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diff --git a/38415.txt b/38415.txt new file mode 100644 index 0000000..be4046e --- /dev/null +++ b/38415.txt @@ -0,0 +1,8791 @@ +Project Gutenberg's Gas-Engines and Producer-Gas Plants, by R. E. Mathot + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Gas-Engines and Producer-Gas Plants + A Practice Treatise Setting Forth the Principles of + Gas-Engines and Producer Design, the Selection and + Installation of an Engine, Conditions of Perfect Operation, + Producer-Gas Engines and Their Possibilities, the Care of + Gas-Engines and Producer-Gas Plants, with a Chapter on + Volatile Hydrocarbon and Oil Engines + +Author: R. E. Mathot + +Commentator: Dugald Clerk + +Translator: Waldemar Kaempffert + +Release Date: December 26, 2011 [EBook #38415] + +Language: English + +Character set encoding: ASCII + +*** START OF THIS PROJECT GUTENBERG EBOOK GAS-ENGINES, PRODUCER-GAS PLANTS *** + + + + +Produced by Erik Reh, Henry Gardiner and the Online +Distributed Proofreading Team at https://www.pgdp.net + + + + + + + * * * * * + +Transcriber's Note: The original publication has been replicated +faithfully except as listed near the end of this text. + +Text in italics is shown like _this_. Text emphasized with bold +characters or other treatment is shown like =this=. + + * * * * * + + + + + Gas-Engines and Producer-Gas Plants + +A PRACTICE TREATISE SETTING FORTH THE PRINCIPLES OF GAS-ENGINES AND +PRODUCER DESIGN, THE SELECTION AND INSTALLATION OF AN ENGINE, CONDITIONS +OF PERFECT OPERATION, PRODUCER-GAS ENGINES AND THEIR POSSIBILITIES, THE +CARE OF GAS-ENGINES AND PRODUCER-GAS PLANTS, WITH A CHAPTER ON VOLATILE +HYDROCARBON AND OIL ENGINES + + BY R. E. MATHOT, M.E. + +Member of the Societe des Ingenieurs Civils de France, Institution of +Mechanical Engineers, Association des Ingenieurs de l'Ecole des Mines du +Hainaut of Brussels + + TRANSLATED FROM ORIGINAL FRENCH MANUSCRIPT BY WALDEMAR B. KAEMPFFERT + + WITH A PREFACE BY DUGALD CLERK, M. INST. C.E., F.C.S. + + ILLUSTRATED + + NEW YORK + MUNN & COMPANY + OFFICE OF THE SCIENTIFIC AMERICAN + 361 BROADWAY + 1905 + + + + + PREFACE TO + + "MATHOT'S GAS-ENGINES AND PRODUCER-GAS PLANTS" + + BY + + DUGALD CLERK, M. INST.C.E., F.C.S. + + +Mr. Mathot, the author of this interesting work, is a well-known Belgian +engineer, who has devoted himself to testing and reporting upon gas and +oil engines, gas producers and gas plants generally for many years past. +I have had the pleasure of knowing Mr. Mathot for many years, and have +inspected gas-engines with him. I have been much struck with the ability +and care which he has devoted to this subject. I know of no engineer +more competent to deal with the many minute points which occur in the +installation and running of gas and oil engines. I have read this book +with much interest and pleasure, and I consider that it deals +effectively and fully with all the principal detail points in the +installation, operation, and testing of these engines. I know of no work +which has gone so fully into the details of gas-engine installation and +up-keep. The work clearly points out all the matters which have to be +attended to in getting the best work from any gas-engine under the +varying circumstances of different installations and conditions. In my +view, the book is a most useful one, which deserves, and no doubt will +obtain, a wide public recognition. + + DUGALD CLERK. + +_March, 1905._ + + + + + INTRODUCTION + + +The constantly increasing use of gas-engines in the last decade has led +to the invention of a great number of types, the operation and care of +which necessitate a special practical knowledge that is not exacted by +other motors, such as steam-engines. + +Explosion-engines, driven by illuminating-gas, producer-gas, oil, +benzin, alcohol and the like, exact much more care in their operation +and adjustment than steam-engines. Indeed, steam-engines are regularly +subjected to comparatively low pressures. The temperature in the +cylinders, moreover, is moderate. + +On the other hand, the explosion-motor is irregularly subjected to high +and low pressures. The temperature of the gases at the moment of +explosion is exceedingly high. It is consequently necessary to resort to +artificial means for cooling the cylinder; and the manner in which this +cooling is effected has a very great influence on the operation of the +motor. If the cooling be effected too rapidly, the quantity of gas +consumed is considerably increased; if the cooling be effected too +slowly, the motor parts will quickly deteriorate. + +In order to reduce the gas consumption to a minimum, a matter which is +particularly important when the motor is driven by street-gas, the +explosive mixture is compressed before ignition. Only if all the parts +are built with joints absolutely gas-tight is it possible to obtain this +compression. The slightest leakage past the valves or around the piston +will sensibly increase the consumption. + +The mixture should be exploded at the exact moment the piston starts on +its working stroke. If ignition occurs too soon or too late, the result +will be a marked diminution in the useful effect produced by the +expansion of the gas. All ignition devices are composed of delicate +parts, which cannot be too well cared for. + +It follows from what has thus far been said that the causes of +perturbation are more numerous in a gas than in a steam engine; that +with a gas-engine, improper care will lead to a much greater increase in +consumption than with a steam-engine, and will cause a waste in power +which would hardly be appreciable in steam-engines, whether their joints +be tight or not. + +It is the purpose of this manual to indicate the more elementary +precautions to be taken in the care of an engine operating under normal +conditions, and to explain how repairs should be made to remedy the +injuries caused by accidents. Engines which are of less than 200 +horse-power and which are widely used in a small way will be primarily +considered. In another work the author will discuss more powerful +engines. + +Before considering the choice, installation, and operation of a +gas-engine, it will be of interest to ascertain the relative cost of +different kinds of motive power. Disregarding special reasons which may +favor the one or the other method of generating power, the net cost per +horse-power hour will be considered in each case in order to show which +is the least expensive method of generating power in ordinary +circumstances. + + R. E. MATHOT. + +MARCH, 1905. + + + + + TABLE OF CONTENTS + + + CHAPTER I + PAGE + MOTIVE POWER AND COST OF INSTALLATION 17 + + + CHAPTER II + + SELECTION OF AN ENGINE + + The Otto Cycle.--The First Period.--The Second Period.--The Third + Period.--The Fourth Period.--Valve Mechanism.--Ignition.-- + Incandescent Tubes.--Electric Ignition.--Electric Ignition by + Battery and Induction-Coil.--Ignition by Magnetos.--The Piston.-- + Arrangement of the Cylinder.--The Frame.--Fly-Wheels.--Straight + and Curved Spoke Fly-Wheels.--The Crank-Shaft.--Cams, Rollers, + etc.--Bearings.--Steadiness.--Governors.--Vertical Engines.-- + Power of an Engine.--Automatic Starting 21 + + + CHAPTER III + + THE INSTALLATION OF AN ENGINE + + Location.--Gas-Pipes.--Dry Meters.--Wet Meters.--Anti-Pulsators, + Bags, Pressure-Regulators.--Precautions.--Air Suction.-- + Exhaust.--Legal Authorization 69 + + + CHAPTER IV + + FOUNDATION AND EXHAUST + + The Foundation Materials.--Vibration.--Air Vibration, etc.-- + Exhaust Noises 87 + + + CHAPTER V + + WATER CIRCULATION + + Running Water.--Water-Tanks.--Coolers 98 + + + CHAPTER VI + + LUBRICATION + + Quality of Oils.--Types of Lubricators 111 + + + CHAPTER VII + + CONDITIONS OF PERFECT OPERATION + + General Care.--Lubrication.--Tightness of the Cylinder.-- + Valve-Regrinding.--Bearings.--Crosshead.--Governor.--Joints.-- + Water Circulation.--Adjustment 121 + + + CHAPTER VIII + + HOW TO START AN ENGINE.--PRELIMINARY PRECAUTIONS + + Care during Operation.--Stopping the Engine 128 + + + CHAPTER IX + + PERTURBATIONS IN THE OPERATION OF ENGINES AND + THEIR REMEDY + + Difficulties in Starting.--Faulty Compression.--Pressure of Water + in the Cylinder.--Imperfect Ignition.--Electric Ignition by + Battery or Magneto.--Premature Ignition.--Untimely + Detonations.--Retarded Explosions.--Lost Motion in Moving + Parts.--Overheated Bearings.--Overheating of the Cylinder.-- + Overheating of the Piston.--Smoke arising from the Cylinder.-- + Back Pressure to the Exhaust.--Sudden Stops 134 + + + CHAPTER X + + PRODUCER-GAS ENGINES + + High Compression.--Cooling.--Premature Ignition.--The Governing + of Engines 153 + + + CHAPTER XI + + PRODUCER-GAS + + Street-Gas.--Composition of Producer-Gases.--Symptoms of + Asphyxiation.--Gradual, Rapid Asphyxiation.--Slow, Chronic + Asphyxiation.--First Aid in Cases of Carbon Monoxide + Poisoning.--Sylvester Method.--Pacini Method.--Impurities of + the Gases 165 + + + CHAPTER XII + + PRESSURE GAS-PRODUCERS + + Dowson Producer.--Generators.--Air-Blast.--Blowers.--Fans.-- + Compressors.--Exhausters.--Washing and Purifying.-- + Gas-Holder.--Lignite and Peat Producers.--Distilling-Producers.-- + Producers Using Wood Waste, Sawdust, and the like.-- + Combustion-Generators.--Inverted Combustion 174 + + + CHAPTER XIII + + SUCTION GAS-PRODUCERS + + Advantages.--Qualities of Fuel.--General Arrangement.-- + Generator.--Cylindrical Body.--Refractory Lining.--Grate and + Support for the Lining.--Ash-pit.--Charging-Box.-- + Slide-Valve.--Cock.--Feed-Hopper.--Connection of Parts.--Air + Supply.--Vaporizer.--Preheaters.--Internal Vaporizers.-- + External Vaporizers.--Tubular Vaporizers.--Partition + Vaporizers.--Operation of the Vaporizers.--Air-Heaters.-- + Dust-Collectors.--Cooler, Washer, Scrubber.--Purifying + Apparatus.--Gas-Holders.--Drier.--Pipes.--Purifying-Brush.-- + Conditions of Perfect Operation of Gas-Producers.-- + Workmanship and System.--Generator.--Vaporizer.--Scrubber.-- + Assembling the Plant.--Fuel.--How to Keep the Plant in Good + Condition.--Care of the Apparatus.--Starting the Fire for the + Gas-Producer.--Starting the Engine.--Care of the Generator + during Operation.--Stoppages and Cleaning 199 + + + CHAPTER XIV + + OIL AND VOLATILE HYDROCARBON ENGINES + + Oil-Engines.--Volatile Hydrocarbon Engines.--Comparative Costs.-- + Tests of High-Speed Engines.--The Manograph.--The Continuous + Explosion-Recorder for High-Speed Engines.--Records 264 + + + CHAPTER XV + + THE SELECTION OF AN ENGINE + + The Duty of a Consulting Engineer.--Specifications.--Testing the + Plant.--Explosion-Recorder for Industrial Engines.--Analysis of + the Gases.--Witz Calorimeter.--Maintenance of Plants.--Test of + Stockport Gas-Engine with Dowson Pressure Gas-Producer.--Test of + a Winterthur Engine.--Test of a Winterthur Producer-Gas + Engine.--Test of a Deutz Producer-Gas Engine and Suction + Gas-Producer.--Test of a 200-H.P. Deutz Suction Gas-Producer and + Engine 279 + + + + + CHAPTER I + + MOTIVE POWER--COST OF INSTALLATION + + +The ease with which a gas-engine can be installed, compared with a +steam-engine is self-evident. In places where illuminating gas can be +obtained and where less than 10 to 15 horse-power is needed, street-gas +is ordinarily employed.[A] The improvements which have very recently +been made in the construction of suction gas-generators, however, would +seem to augur well for their general introduction in the near future, +even for very small powers. + +The installation of small street-gas-engines involves simply the making +of the necessary connections with gas main and the mounting of the +engine on a small base. + +An economical steam-engine of equal power would necessitate the +installation of a boiler and its setting, the construction of a +smoke-stack, and other accessories, while the engine itself would +require a firm base. Without exaggeration it may be asserted that the +installation of a steam-engine and of its boiler requires five times as +much time and trouble as the installation of a gas-engine of equal +power, without considering even the requirements imposed by storing the +fuel (Fig. 1). Small steam-engines mounted on their own boilers, or +portable engines, the consumption of which is generally not economical, +are not here taken into account. + +[Illustration: FIG. 1.--30 H.P. Gas-engine and suction gas-producer.] + +[Illustration: FIG. 1_A_.--30 H.P. Steam-engine, boiler and smoke-stack.] + +So far as the question of cost is concerned, we find that a 15 to 20 +horse-power steam-engine working at a pressure of 90 pounds and having a +speed of 60 revolutions per minute would cost about 16-2/3 per cent. +more than a 15 horse-power gas-engine, with its anti-pulsators and other +accessories. The foundation of the steam-engine would likewise cost +about 16-2/3 per cent. more than that of the gas-engine. Furthermore the +installation of the steam-engine would mean the buying of piping, of a +boiler of 100 pounds pressure, and of firebrick, and the erection of a +smoke-stack having a height of at least 65 feet. Beyond a little +excavating for the engine-base and the necessary piping, a gas-engine +imposes no additional burdens. It may be safely accepted that the +steam-engine of the power indicated would cost approximately 45 per +cent. more than the gas-engine of corresponding power. + +The cost of running a 15 to 20 horse-power steam-engine is likewise +considerably greater than that of running a gas-engine of the same size. +Considering the fuel-consumption, the cost of the lubricating oil +employed, the interest on the capital invested, the cost of maintenance +and repair, and the salary of an engineer, it will be found that the +operation of the steam-engine is more expensive by about 23 per cent. + +This economical advantage of the gas over the steam-engine holds good +for higher power as well, and becomes even more marked when +producer-gas is used instead of street-gas. Comparing, for example, a 50 +horse-power steam-engine having a pressure of 90 pounds and a speed of +60 revolutions per minute, with a 50 horse-power producer-gas engine, +and considering in the case of the steam-engine the cost of a boiler of +suitable size, foundation, firebrick, smoke-stack, etc., and in the case +of the gas-engine the cost of the producer, foundation, and the like, it +will be found that the installation of a steam-engine entails an +expenditure 15 per cent. greater than in the case of the producer-gas +engine. However, the cost of operating and maintaining the steam-engine +of 50 horse-power will be 40 per cent. greater than the operation and +maintenance of the producer-gas engine. + +From the foregoing it follows that from 15 to 20 up to 500 horse-power +the engine driven by producer-gas has considerably the advantage over +the steam-engine in first cost and maintenance. For the development of +horse-powers greater than 500, the employment of compound +condensing-engines and engines driven by superheated steam considerably +reduces the consumption, and the difference in the cost of running a +steam- and gas-engine is not so marked. Still, in the present state of +the art, superheated steam installations entail considerable expense for +their maintenance and repair, thereby lessening their practical +advantages and rendering their use rather burdensome. + + + FOOTNOTES: + +[A] Recent improvements made in suction gas-producers will probably lead +to the wide introduction of producer gas engines even for small power. + + + + + CHAPTER II + + THE SELECTION OF AN ENGINE + + +Explosion-engines are of many types. Gas-engines, of the four-cycle +type, such as are industrially employed, will here be principally +considered. + +=The Otto Cycle.=--The term "four-cycle" motor, or Otto engine, has its +origin in the manner in which the engine operates. A complete cycle +comprises four distinct periods which are diagrammatically reproduced in +the accompanying drawings. + +=The First Period.=--_Suction:_ The piston is driven forward, creating a +vacuum in the cylinder, and simultaneously drawing in a certain quantity +of air and gas (Fig. 2). + +[Illustration: FIG. 2.--First cycle: Suction.] + +=The Second Period.=--_Compression:_ The piston returns to its initial +position. All admission and exhaust valves are closed (Fig. 3). The +mixture drawn in during the first period is compressed. + +=The Third Period.=--_Explosion and Expansion:_ When the piston has +reached the end of its return stroke, the compressed mixture is ignited. +Explosion takes place at the dead center. The expansion of the gas +drives the piston forward (Fig. 4). + +[Illustration: FIG. 3.--Second cycle: Compression.] + +[Illustration: FIG. 4.--Third cycle: Explosion and expansion.] + +=The Fourth Period.=--_Exhaust:_ The piston returns a second time. The +exhaust-valve is opened, and the products of combustion are discharged +(Fig. 5). + +[Illustration: FIG. 5.--Fourth cycle: Exhaust.] + +These various cycles succeed one another, passing through the same +phases in the same order. + +=Valve Mechanism.=--It is to be noted that in modern motors valves are +used which are better adapted to the peculiarities of explosion-engines +than were the old slide-valves used when the Otto engine was first +introduced. The slide-valve may now be considered as an antiquated +distributing device with which it is impossible to obtain a low +consumption. + +In old-time gas-engines rather low compressions were used. Consequently +a very low explosive power of the gaseous mixture, and low temperatures +were obtained. The slide-valves were held to their seats by the pressure +of external springs, and were generously lubricated. Under these +conditions they operated regularly. Nowadays, the necessity of using +gas-engines which are really economical has led to the use of high +compressions with the result that powerful explosions and high +temperatures are obtained. Under these conditions slide-valves would +work poorly. They would not be sufficiently tight. To lubricate them +would be difficult and ineffective. Furthermore, large engines are +widely used in actual practice, and with these motors the frictional +resistance of large slide-valves, moving on extensive surfaces would be +considerable and would appreciably reduce the amount of useful work +performed. + +[Illustration: FIG. 6.--Modern valve mechanism.] + +By reason of its peculiar operation, the slide-valve is objectionable, +the gases being throttled at the time of their admission and discharge. +As a result of these objections there are losses in the charge; and +obnoxious counter-pressures occur. The necessity of using elements +simple in their operation and free from the objections which have been +mentioned, has naturally led to the adoption of the present valve. This +valve is used both for the suction of the gas and of the air, as well as +for the exhaust, with the result that either of these two essential +phases in the operation of the motor can be independently controlled. +The valves offer the following advantages: Their tightness increases +with the pressure, since they always open toward the interior of the +cylinder (Fig. 6). They have no rubbing surfaces, and need not, +therefore, be lubricated. Their opening is controlled by levers provided +with quick-acting cams; and their closure is effected by coiled springs +almost instantaneous in their action (Fig. 7). Each valve, depending +upon the purpose for which it is used, can be mounted in that part of +the cylinder best suited for its particular function. The types of +valved motors now used are many and various. In order to attain economy +in consumption and regularity in operation they should meet certain +essential requirements which will here be reviewed. + +Apart from proportioning the areas properly and from providing a +suitable means of operation, it is indispensable that the valves should +be readily accessible. Indeed, the valves should be regularly examined, +cleaned and ground. It follows that it should be possible to take them +apart easily and quickly. + +[Illustration: FIG. 7.--Controlling mechanism of valve.] + +It is necessary that the exhaust-valve be well cooled; otherwise the +valve, exposed as it is to high temperatures, will suffer derangement +and may cause leakage. The water-jacket should, therefore, surround the +seat of the exhaust-valve, care being taken that the cooling water be +admitted as near to it as possible (Fig. 8). The motor should control +the air-let valve or that of the gaseous mixture. Hence these valves +should not be actuated simply by springs, because springs are apt to +move under the influence of the vacuum produced by suction. + +[Illustration: FIG. 8.--Water-jacketed valve.] + +The mixture of gas and air should not be admitted into the cylinder at +too low a pressure; otherwise the weight of the mixture admitted would +be lower than it ought to be, inasmuch as under these conditions the +valve will be opened too tardily and closed prematurely. At the +beginning as well as at the end of its stroke the linear velocity of the +piston is quite inadequate to create a vacuum sufficient to overcome the +resistance of the spring. It is, therefore, generally the practice +separately to control the opening or closing of the one or the other +valve (gas-valve or mixture-valve). Consequently these valves must be +actuated independently of each other. Nowadays they are mechanically +controlled almost exclusively,--a method which is advocated by +well-known designers for industrial motors in particular. Valves which +are not actuated in this manner (free valves) have only the advantage of +simplicity of operation. Nevertheless, this arrangement is still to be +found in certain oil and benzine engines, notably in automobile-motors. +In these motors it is necessary to atomize the liquid fuel by means of +aspired air, in order to produce an explosive, gaseous mixture. + +=Ignition.=--In the development of the gas-engine, the incandescent tube +and the electric spark have taken the place of the obsolete naked flame. +The last-mentioned mode of exploding the gaseous mixture will not, +therefore, be discussed. + +The hot tube of porcelain or of metal has the indisputable merit of +regularity of operation. The methods by which this operation is made as +perfect as possible are many. Since certainty of ignition is obtained by +means of the tube, it is important to time the ignition, so that it +shall occur exactly at the moment when the piston is at the dead +center. It has been previously stated that premature or belated ignition +of the explosive mixture appreciably lessens the amount of useful work +performed by the expansion of the gas. If ignition occur too soon, the +mixture will be exploded before the piston has reached the dead center +on its return stroke. As a result, the piston must overcome a +considerable resistance due to the premature explosion and the +consequent pressure. Furthermore, by reason of the high temperature of +explosion, the gaseous products are very rapidly cooled. This rapid +cooling causes a sudden drop in the pressure; and since a certain +interval elapses between the moment of explosion and the moment when the +piston starts on its forward stroke, the useful motive effort is the +more diminished as the ignition is more premature. + +=Incandescent Tubes.=--In Figs. 9 and 10 two systems most commonly used +are illustrated. In these two arrangements, in which no valve is used, +the length or height to which the tube is heated by the outer flame is +so controlled that the gaseous mixture, which has been driven into the +tube after compression, reaches the incandescent zone as nearly as +possible at the exact moment when ignition and explosion should take +place. The temperature of the flame of the burner, the richness of the +gaseous mixture, and other circumstances, however, have a marked +influence on the time of ignition, so that the mixture is never fired at +the exact moment mentioned. + +[Illustration: FIGS. 9-10.--Valveless hot tubes.] + +These considerations lead to the conclusion that motors in which the +mixture is exploded by hot tubes provided with an ignition-valve are +preferable to valveless tubes. By the use of a special valve, positively +controlled by the motor itself, the chances of untimely ignition are +lessened, because it is necessary simply to regulate the temperature and +the position of the tube in order that ignition may be surely effected +immediately upon the opening of the valve, at the very moment the +cylinder gases come into contact with the incandescent portion of the +tube (Fig. 11). Many manufacturers, however, do not employ the +ignition-valve on motors of less than 15 to 20 horse-power, chiefly +because of the cheaper construction. The total consumption is of less +moment in a motor of small than of great power, and the loss due to the +lack of an ignition-valve not so marked. In a high-power engine, +premature explosion may be the cause of the breaking of a vital part, +such as the piston-rod or the crank-shaft. For this reason, a valve is +indispensable for engines of more than 20 to 25 horse-power. A breakage +of this kind is less to be feared in a small motor, where the parts are +comparatively stout. The gas consumption of a well-designed burner does +not exceed from 3.5 to 5 cubic feet per hour. + +[Illustration: FIG. 11.--Ignition-tube with valve.] + +=Electric Ignition.=--Electric ignition consists in producing a spark in +the explosion-chamber of the engine. The nicety with which it can be +controlled gives it an undeniable advantage over the hot tube. But the +objection has been raised, perhaps with some force, that it entails +certain complications in installing the engine. Its opponents even +assert that the power and the rapidity of the deflagration of the +explosive mixture are greater with hot-tube ignition. This reason may +have caused the hot-tube system to prevail in England, where +manufacturers of gas-engines are very numerous and not lacking in +experience. + +Electric ignition is effected in gas-engines by means of a battery and +spark-coil, or by means of a small magneto machine which mechanically +produces a current-breaking spark. + +[Illustration: FIG. 12.--Electric ignition by spark-coil and battery.] + +[Illustration: FIG. 13.--Spark-plug.] + +=Electric Ignition by Battery and Induction-Coil.=--The first system is +the cheaper; but it exacts the most painstaking care in maintaining the +parts in proper working condition. It comprises three essential +elements--a battery, a coil, and a spark-plug (Fig. 12). The battery may +be a storage-battery, which must, consequently, be recharged from time +to time; or it may be a primary battery which must be frequently +renewed and carefully cleaned. The induction-coil is fitted with a +trembler or interrupter, which easily gets out of order and which must +be regulated with considerable accuracy. The spark-plug is a +particularly delicate part, subject to many possible accidents. The +porcelain of which it is made is liable to crack. It is hard to obtain +absolutely perfect insulation; for the terminals deteriorate as they +become overheated, break, or become foul (Fig. 13). In oil-engines, +especially, soot is rapidly deposited on the terminals, so that no spark +can be produced. In benzine or naphtha motors, such an accident is less +likely to happen. In automobile-motors, however, the spark-plug only too +often fails to perform its function. The one remedy for these evils is +to be found in the most painstaking care of the spark-plug and of the +other elements of the ignition system. + +[Illustration: FIG. 14.--Magneto ignition apparatus.] + +[Illustration: FIG. 15.--General view and details of a magneto ignition +apparatus.] + +=Ignition by Magnetos.=--Magneto apparatus, on the other hand, are +noteworthy for the regularity of their operation. They may be used for +several years without being remagnetized, and require no exceptional +care. Magneto ignition devices are mechanically actuated, the necessary +displacement of the coil being effected by means of a cam carried on a +shaft turning with half the motor speed (Figs. 14 and 15). At the moment +when it is released by the cam, the coil is suddenly returned to its +initial position by means of a spring. This rapid movement generates a +current that passes through terminals, which are arranged within the +cylinder and which are immediately separated by mechanical means. Thus a +much hotter circuit-breaking spark is produced, which is very much more +energetic than that of a battery and induction-coil, and which surely +ignites the gaseous mixture in the cylinder. The terminals are generally +of steel, sometimes pointed with nickel or platinum (Fig. 16). The only +precaution to be observed is the exclusion of moisture and occasional +cleaning. For engines driven by producer-gas magneto-igniters are +preferable to cells and batteries. In general, electrical ignition is to +be recommended for high-pressure engines. + +[Illustration: FIG. 16.--Contacts of a magneto-igniter.] + +[Illustration: FIG. 17.--Device for regulating the moment of ignition.] + +In order to explain more clearly modern methods of ignition a diagram is +presented, showing an electric magneto-igniter applied to the +cylinder-head of a Winterthur motor, and also a sectional view of the +member varying the make-and-break contacts which are mounted in the +explosion-chamber (Figs. 18 and 19) + +1. The magneto _A_ consists of horseshoe-magnets, between the poles of +which the armature rotates. At its conically turned end, the +armature-shaft carries an arm _B_, held in place by a nut. + +[Illustration: FIG. 18.--Winterthur electric ignition system.] + +2. The igniter _C_ is a casting secured to the cylinder-head by a +movable strap and provided with two axes _D_ and _M_, of which the one, +_D_, made of bronze, is movable, and is fitted with a small interior +contact-hammer, a percussion-lever, and an exterior recoil-spring; the +other, _M_, is fixed, insulated, and arranged to receive the current +from the magneto _A_, by means of an insulated copper wire _E_. + +3. The spring _F_ comprises two continuous coils contained in a brass +casing, and actuating a steel striking or percussion-pin. + +4. The controlling devices of the magneto include a stem or rod _G_, +slidable in a guide _H_, provided with a safety spring and mounted on an +eccentric spindle, the position of which can be varied by means of a +regulating-lever (_I_). The rod is operated from the distributing-shaft, +on the conical end of which a cam _J_ carrying a spindle is secured. + +[Illustration: FIG. 19.--Contacts of the Winterthur system.] + +_Regulation of the Magneto._--The position assumed by the armature when +at rest is a matter of importance in obtaining a good spark on breaking +the circuit. The marks on the armature should be noted. The position of +the armature may be experimentally varied, in order to obtain a spark of +maximum intensity, by changing the position of the arm B on the +armature-shaft. + +_Control of the Magneto._--The controlling gear should enable the +armature to oscillate from 20 to 25 degrees. The time at which the +breaking of the circuit is effected can be regulated by shifting the +handle (_I_). In starting the engine, the circuit can be broken with a +slight retardation, which is lessened as the engine attains its normal +speed. + +_Igniter._--It is advisable that there should be a play of 1/2 mm. +(0.0196 in.) between the lever _Z_ when at rest and the striking-pin. +The axis _D_ of the circuit-breaking device should be easily movable; +and the hammer which it carries at its end toward the interior of the +cylinder should be in perfect contact with the stationary spindle _M_, +which is electrically insulated. This spindle _M_ should be well +enclosed, in order to prevent any leakage that might cause a +deterioration of the insulating material. + +The subject of ignition is of such extreme importance that the author +will recur to it from time to time in the various chapters of this book. +Too much stress cannot be laid upon proper timing; otherwise there will +be a needless waste of power. Cleanliness is a point that must be +observed scrupulously; for spark-plugs are apt to foul only too readily, +with the result that short-circuits and misfires are apt to occur. In +oil and volatile hydrocarbon engines the tendency to fouling is +particularly noticeable. In the chapter devoted to these forms of +motors the author has dwelt upon the precautions that should be taken to +forestall a possible derangement of the ignition apparatus. As a general +rule the ignition apparatus installed by trustworthy manufacturers will +be found best suited for the requirements of the engine. + +The apparatus should be fitted with a device by which the ignition can +be duly timed by hand during operation (Fig. 17). + +[Illustration: FIG. 20.--Design of the piston.] + +=The Piston.=--Coming, as it does, continually in contact with the +ignited gases, the piston is gradually heated to a high temperature. The +rear face of the piston should preferably be plane. Curved surfaces are +not to be recommended because they cool off badly. Likewise, faces +having either inserted parts or bolt-heads are to be avoided, since they +are liable to become red-hot and to ignite the mixture prematurely (Fig. +20). + +[Illustration: FIG. 21.--Piston with lubricated pin.] + +Among the parts of the piston which rapidly wear away because constant +lubrication is difficult, is the connection with the piston-rod (Fig. +21). It is important that the bearing at the piston-pin be formed of two +parts which can be adjusted to take up the wear. The pin itself should +be of case-hardened steel. For large engines, some manufacturers have +apparently abandoned the practice of locking the pin, by set-screws, in +flanges cast in one piece with the piston. Indeed, the piston is often +fractured by reason of the expansion of the pins thus held on two sides. +It seems advisable to secure the pin by means of a single screw in one +of the flanges, fitting it by pressure against the opposite boss. The +use of wedges or of clamping-screws, introduced from without the piston +to hold the pin, should be avoided. It may happen that the wedges will +be loosened, will move out, and will grind the cylinder, causing +injuries that cannot be detected before it is too late. The strength of +the piston-pin should be so calculated that the pressure per square inch +of projected surface does not exceed 1,500 to 2,850 pounds per square +inch. It should be borne in mind that the initial pressure of the +explosion is often equal to 400 to 425 pounds per square inch. Some +manufacturers mount the pin as far to the back of the piston as +possible, so as to bring it nearer the point of application of the +motive force of the explosion. Other manufacturers, on the other hand, +mount the pin toward the front of the piston. No great objection can be +raised against either method. In the former case the position of the +rings will limit that of the pin. + +The number of these rings ought not to be less than four or five, +arranged at the rear of the piston. It is to be observed that makers of +good engines use as many as 8 to 10 rings in the pistons of fair-sized +motors. + +Piston-rings of gray pig-iron can be adjusted with the greatest nicety +in such a manner that, by means of tongues fitting in their grooves, +they are held from turning in the latter, whereby their openings are +prevented from registering and allowing the passage of gas. As a general +rule, a large number of rings may be considered a distinguishing feature +of a well-built engine. In order to prevent a too rapid wear of the +cylinder, several German manufacturers finish off the front of the +piston with bronze or anti-friction metal in engines of more than 40 to +50 horse-power. It is to be observed, however, that this expedient is +not applicable to motors the cylinders of which are comparatively cold; +otherwise the bronze or anti-friction metal will deteriorate. + +=Arrangement of the Cylinder.=--The cylinder shell or liner, in which +the piston travels, and the water-jacket should preferably be made in +separate pieces and not cast of the same metal, in order to permit a +free expansion (Figs. 22 and 23). If for want of care or of proper +lubrication, which frequently occurs in gas-engines, the cylinder should +be injured by grinding, it can be easily renewed, without the loss of +all the connecting parts. + +[Illustration: FIG. 22.--Head, jacket and liner of cylinder, cast in one +piece.] + +[Illustration: FIG. 23.--Cylinder with independent liner and head.] + +For the same reason, the cylinder and its casing should be independent +of the frame. In many horizontal engines, the cylinders overhang the +frame throughout the entire length, by reason of the joining of their +front portions with the frames. Although such a construction is attended +with no serious consequences in small engines, nevertheless in large +engines it is exceedingly harmful. Indeed, in most modern single-acting +engines, the pistons are directly connected with the crank-shaft by the +piston-rod, without any intermediate connecting-rod or cross-head. The +vertical reaction of the motive effort on the piston is, therefore, +taken up entirely by the thrust of the cylinder, which is also vertical +(Fig. 24). This thrust, acting against an unsupported part, may cause +fractures; at any rate, it entails a rapid deterioration of the cylinder +joint. + +[Illustration: FIG. 24.--Single-acting engines.] + +[Illustration: FIG. 25.--Engine with inclined bearings.] + +=The Frame.=--Gas-engines driven as they are, by explosions, giving rise +to shocks and blows, should be built with frames, heavy, substantial, +and broad-based, so as to rest solidly on the ground. This essential +condition is often fulfilled at the cost of the engine's appearance; but +appearance will be willingly sacrificed to meet one of the requirements +of perfect operation. For engines of more than 8 to 10 horse-power, +frames should be employed which can be secured to the masonry foundation +without a separate pedestal or base. Some manufacturers, for the purpose +of lightening the frame, attach but little importance to the foundation +and to strength of construction, and employ the design illustrated in +place of the crank-shaft bearing (Fig. 25); others, in order to +facilitate the adjusting of the connecting-rod bearings, prefer the +second form (Fig. 26). It is evident that, in the first case, a part of +the effort produced by the explosion reacts on the upper portion of the +connecting-rod bearing, on the cap of the crank-shaft bearing, and +consequently on the fastening-bolts. In the second case, if the +adjustment be not very carefully made, or if the rubbing surfaces are +insufficient, the entire thrust due to the explosion will be received +by the meeting parts of the two bushings, thus injuring them and causing +a more rapid wear. In the construction of large engines, some +manufacturers take the precaution of forming the connecting-rod bearings +of four parts, adjustable to take up the wear, so that the effort is +exerted against the parts disposed at right angles to each other. A form +that seems rational is that shown in Fig. 27, in which the reaction of +the thrust is taken up by the lower bearing, rigidly supported by the +braced frame, in the direction opposite to that of the explosive effort. + +[Illustration: FIG. 26.--Engine with straight bearings.] + +[Illustration: FIG. 27.--Engine with correctly designed bearings.] + +The sum of the projecting surfaces of the two bearings should be so +calculated that a maximum explosive pressure of 405 to 425 pounds per +square inch will not subject the bearings to a pressure higher than 425 +to 550 pounds per square inch. + +=Fly-Wheels.=--In gas-engines particularly, the fly-wheel should be +secured to the crank-shaft with the utmost care. It should be mounted as +near as possible to the bearings; otherwise the alinement of the shaft +will be destroyed and its strength impaired. If the fly-wheel be +fastened by means of a key or wedge having a projecting head, it is +advisable to cover the end of the shaft by a movable sleeve. The +fly-wheel should run absolutely true and straight even if the explosion +be premature. In well-built engines the fly-wheels are lined up and +shaped to the rim. The periphery is slightly rounded in order the better +to guide the belt when applied to the wheel. + +[Illustration: FIG. 28.--Single fly-wheel engine with external bearing.] + +Furthermore, fly-wheels should be nicely balanced; those are to be +preferred which have no counter-weights cast or fastened to the hub, the +spokes, or the rim. The system of balancing the engine by means of two +fly-wheels, mounted on opposite sides, is used chiefly for the purpose +of equalizing the inertia effects. Special engines, employed for driving +dynamos, and even industrial engines of high power, are preferably +fitted with but a single fly-wheel, with an outer bearing, since they +more readily counteract the cyclic irregularities or variations of speed +occurring in a single revolution (Fig. 28). If in this case a pulley be +provided, it should be mounted between the engine and the outer +bearing. The following advantages may be cited in favor of the single +fly-wheel, particularly in the case of dynamo-driving engines: + +1. The single fly-wheel permits a more ready access to the parts to be +examined. + +2. It involves the employment of a third bearing, thus avoiding the +overhang caused by two ordinary fly-wheels. + +3. It avoids the torsional strain to which the two-wheel crank is +subjected when starting, stopping, and changing the load, the peripheral +resistance varying in one of the fly-wheels, while the other is +subjected to a strain in the opposite direction on account of the +inertia. + +4. Two fly-wheels, keyed as they are to projecting ends of the shaft, +will be so affected at the rims by the explosions that the belts will +shake. + +The third bearing which characterizes the single-fly-wheel system, is +but an independent support, resting solidly on the masonry bed of the +engine. The bearing with its independent support is sufficiently rigid, +and is not subjected to any stress from the crank at the moment of +explosion, the reaction of the crank affecting only the frame bearings. +With such fly-wheels, reputable firms guarantee a cyclic regularity +which compares favorably with that of the best steam-engines. For a duty +varying from a third of the load to the maximum load, these engines, +when driving direct-current dynamos for directly supplying an +electric-light circuit, will insure perfect steadiness of the light; +and the effectually aperiodic measuring instruments will not indicate +fluctuations greater than 2 to 3 per cent. of the tension or intensity +of the current. The coefficient of the variations in the speed of a +single revolution will thus be not far from 1/60. + +[Illustration: FIG. 29.--Curved spoke fly-wheel.] + +=Straight and Curved Spoke Fly-Wheels.=--The spokes of fly-wheels are +either straight or curved. In assembling the motor parts it too often +occurs that curved spoke fly-wheels are mounted with utter disregard of +the direction in which they are to turn. It is important that curved +spokes should be subjected to compression and not to traction. Hence the +fly-wheels should be so mounted that the concave portions of the spokes +travel in the direction of rotation, as shown in the accompanying +diagram (Fig. 29). If a single fly-wheel be employed on an engine of the +type in which the speed is governed by the "hit-and-miss" system, the +fly-wheel should be extra heavy to counteract the irregularities of the +motive impulses when the engine is not working at its full load, or in +other words, when no explosion takes place at every cycle. + +[Illustration: FIG. 30.--Forged crank-shafts.] + +=The Crank-Shaft.=--The crank-shaft should be made of the best mild +steel. Those shafts are to be preferred the cranks of which are not +forged on (Fig. 30), but cut out of the mass of metal; furthermore, the +brackets or supports should be planed and shaped so that they are square +in cross-section. + +[Illustration: FIG. 31.--Correct design of crank-shaft.] + +Such a design involves fine workmanship and speaks well for the +construction of the whole engine. Moreover, it enables the bearings to +be brought nearer each other, reduces to a minimum that part of the +crank-shaft which may be considered the weakest, and permits a rational +and exact counterbalancing of the moving parts, such as the crank and +the end of the connecting-rod. The best manufacturers have adopted the +method of fastening to the cranks balancing weights secured to the +brackets, especially for high-speed engines or for engines of high +power. The projecting surface of the crank-pin should, as a rule, be +calculated for a pressure of 1,400 pounds per square inch. + +[Illustration: FIG. 32.--Crank-shaft with balancing weight.] + +=Cams, Rollers, etc.=--The cams, rollers, thrust-bearings, as well as +the piston-pin in particular, should be made of good steel, +case-hardened to a depth of at least .08 of an inch. Their hardness and +the degree of cementation may be tested by means of a file. This is the +method followed by the best manufacturers. + +=Bearings.=--All the bearings and all guides should be adjustable to +take up the wear. They are usually made of bronze or of the best +anti-friction metal. + +=Steadiness.=--The steadiness of engines may be considered from two +different standpoints. + +[Illustration: FIG. 33.--Inertia governor.] + +1. _Variation of the Number of Revolutions at Different Loads._--This +depends chiefly on the sensitiveness of the governor, which should be of +the "inertia" or of the "ball" (or centrifugal) type. The first form is +rarely employed, except in small engines up to 10 horse-power, and is +applicable only to engines in which the "hit and miss" system is +employed (Fig. 33). The second form is more widely used, and is +applicable to engines having "hit-and-miss" or variable admission +devices. In the first form, the governor simply displaces a very light +member, whatever may be the size of the engine, for which reason the +dimensions are very small. In the second form, on the other hand, the +governor acts either on a conical sleeve or on some other regulating +member offering resistance. Evidently, in order to overcome the +reactions to which it is subjected, it must be as heavy and powerful as +a steam-engine governor. Sufficient allowance is made in a good engine +for variation in the number of revolutions between no load and full +load, not greater than two per cent. if the admission be of the +"hit-and-miss" type, and five per cent. if it be of the variable type. + +2. _Cyclic Regularity._--This term means simply that the speed of the +engine is constant in a single revolution. In practice this is never +attained. Allowance is made in engines used for driving direct-current +dynamos for a variation of about 1/60; while in industrial engines a +variation of 1/25 is permissible. Cyclic variation depends only on the +weight of the fly-wheel; whereas variation in the number of revolutions +is determined chiefly by the governor. + +=Governors.=--Diagrams are here presented of the principal types of +governors--the inertia governor, the ball or centrifugal governor +controlling an admission-valve of the "hit-and-miss" type (Fig. 34), and +the ball or centrifugal governor controlling a variable gas-admission +valve (Fig. 35). + +In distinguishing between the operation of the two last-mentioned types, +it may be stated that the former bears the same relation to the +hit-and-miss gear as it does, for example, to the valve gear of a +Corliss steam-engine. In other words, it is an apparatus that +_indicates_ without _inducing_, admission or cut-off. The second type, +on the other hand, operates by means of slides and the like, as in the +Ridder type of engine, in which it controls the displacement of the +cut-off or distribution slide-valve and is subjected to variable forces, +depending on the pressure, lubrication, the condition of the +stuffing-boxes, and the like. + +In gas as well as in steam engines, designs are to be commended which +shield the delicate mechanism from strains and stresses that are likely +to destroy its sensitiveness, as is the case in the automatic cut-off of +the Corliss steam-engine. + +[Illustration: FIG. 34.--"Hit-and-miss" governor.] + +Governors should be provided with means to permit the manual variation +of the speed while the engine is in operation. + +For small motors, one of the most widely used admission devices is that +of the "hit-and-miss" type. As its name indicates, this admission +arrangement allows a given quantity of gas to enter the cylinder for a +number of consecutive intervals, until the engine is about to exceed its +normal speed. Thereupon the governor cuts off the gas entirely. The +result is that, in this system, the number of admissions is variable, +but that each admitted charge is composed of a constant proportion of +gas and air. + +The governors employed for the "hit-and-miss" type are either "inertia" +or "centrifugal" governors. + +Inertia governors (Fig. 33) are less sensitive than those of the +centrifugal type. They are generally applied only to industrial engines +of small power, in which regularity of operation is a secondary +consideration. + +Centrifugal governors employed for gas-engines with "hit-and-miss" +regulation are, as a general rule, noteworthy for their small size, +which is accounted for by the fact that, in most systems, merely a +movable member is placed between the admission-controlling means and the +valve-stem (Fig. 34). It follows that this method of operation relieves +the governor of the necessity of overcoming the resistance of the weight +of moving parts, more or less effectually lubricated, and subjected to +the reaction of the parts which they control. + +In engines equipped with variable admission devices for the gas or the +explosive mixture, the governor actuates a sleeve on which the +admission-cam is fastened (Fig. 35). Or, the governor may displace a +conical cam, the reaction of which, on contact with the lever, destroys +the stability of the governor. These conditions justify the employment +of powerful governors which, on account of the inertia of their parts, +diminish the reactionary forces encountered. + +The centrifugal governor should be sufficiently effectual to prevent +variations in the number of revolutions within the limits of 2 to 3 per +cent. between no load and approximately full load. Under equivalent +conditions, the inertia governor can hardly be relied upon for a +coefficient of regularity greater than 4 to 5 per cent. + +[Illustration: FIG. 35.--Variable admission governor.] + +The manner of a governor's operation is necessarily dependent on the +admission system adopted. And the admission system varies essentially +with the size, the purpose of the engine, and the character of the fuel +employed. + +[Illustration: FIG. 36.--Vertical engine.] + +[Illustration: FIG. 37.--Section through an engine of the vertical or +"steam-hammer" type.] + +=Vertical Engines.=--For some years past there seems to have been a +tendency in Europe to use horizontal instead of vertical engines, +especially since engines of more than 10 or 15 horse-power have been +extensively used for industrial purposes. The vertical type is used for +1 to 8 horse-power engines, with the cylinder in the lower part of the +frame, and the shaft and its fly-wheel in the upper part (Fig. 36). The +only merit to be attributed to this arrangement is a great saving of +space. It is evident, however, that beyond a certain size and power, +such engines are unstable. In America particularly, many manufacturers +of high-power engines (50 to 100 horse-power or more) prefer the +vertical or "steam-hammer" arrangement, which consists in placing the +cylinder in the upper part, and the shaft in the lower part of the frame +as close to the ground as possible (Figs. 37 and 38). The problem of +saving space, as well as that of insuring stability, is thus solved, so +that it is easily possible to run up the speed of the engine. There is +also the advantage that the shaft of a dynamo can be directly coupled +up with the crank-shaft of the engine, thus dispensing with a belt, +which, at the least, absorbs 4 to 6 per cent. of the total power. It +should, nevertheless, be borne in mind that the direct coupling of +electric generators to engine-shafts implies the use of extremely large +and, therefore, of extremely costly dynamos. Furthermore, by reason of +this arrangement, groups of electro-generators can be disposed in a +comparatively small amount of space. Some English manufacturers are also +beginning to adopt the "steam-hammer" type of engine for high powers, +the result being a marked saving in material and lowering of the cost of +installation. + +[Illustration: FIG. 38.--Side and end elevations of a vertical or +"steam-hammer" engine.] + +=Power of the Engine.=--The first thing to be considered is that the +power of a gas-engine is always given in "effective" horse-power, and +that the power of a steam-engine is always given in "indicated" +horse-power in contracts of sale. In England and in the United States, +the expression "nominal" horse-power is still employed. It may be +advisable to define these various terms exactly, since unscrupulous +dealers, to the buyer's loss, have done much to confuse them. + +"Indicated" horse-power is a designation applied to the theoretical +power produced by the action of the motive agent on the piston. The work +performed is measured on an indicator card, by means of which the +average pressure to be considered in the computation of the theoretical +power is ascertained. + +The "effective" or brake horse-power is equal to the "indicated" +horse-power, less the energy absorbed by passive resistance, friction of +the moving parts, etc. + +The "effective" work is an experimental term applied to the power +actually developed at the shaft. This work is of interest solely to the +engine user. + +In a well-built motor, in which the passive resistance by reason of the +correct adjustment and simplicity of the parts, is reduced to a minimum, +the "effective" horse-power is about 80 to 87 per cent. of the +"indicated" horse-power, when the engine runs under full load. This +reduced output is usually called the "mechanical efficiency" of the +engine. + +"Nominal" horse-power is an arbitrary term in the sense in which it is +used in England and America, where it is quite common. The manufacturers +themselves do not seem to agree on its absolute value. A "nominal" +horse-power, however, is equal to anything from 3 to 4 "effective" +horse-power. The uncertainty which ensues from the use of the term +should lead to its abandonment. + +In installing a motor, the determination of its horse-power is a matter +of grave importance, which should not be considered as if the motor were +a steam-engine or an engine of some other type. It must not be forgotten +that, especially at full load, explosion-engines are most efficient, and +that, under these conditions, it will generally be advisable to +subordinate the utility of having a reserve power to the economy which +follows from the employment of a motor running at a load close to its +maximum capacity. On the other hand, the gas-engine user is unwilling to +believe that the stipulated horse-power of the motor which is sold to +him is the greatest that it is capable of developing under industrial +conditions. Business competition has led some firms to sell their +engines to meet these conditions. It is probably not stretching the +truth too far to declare that 80 per cent. of the engines sold with no +exact contract specifications are incapable of maintaining for more than +a half hour the power which is attributed to them, and which the buyer +expects. It follows that the power at which the engine is sold should be +both industrially realized and maintained, if need be, for an entire +day, without the engine's showing the slightest perturbation, or +faltering in its silent and regular operation. To attain this end, it is +essential that the energy developed by the engine in normal or constant +operation should not exceed 90 to 95 per cent. of the maximum power +which it is able to yield, and which may be termed its "utmost power". +As a general rule, especially for installations in which the power +fluctuates from the lowest possible to double this, as much attention +must be paid to the consumption at half load as at full load; and +preference should be given to the engine which, other things being +equal, will operate most economically at its lowest load. In this case +the consumption per effective horse-power is appreciably higher. +Generally, this consumption is greater by 20 to 30 per cent. than that +at full load. This is particularly true of the single-acting engines so +widely used for horse-powers less than 100 to 150. + +In some double or triple-acting engines, according to certain writers, +the diminution in the consumption will hardly be proportional to the +diminution of the power, or at any rate, the difference between the +consumption per B.H.P. at full load and at reduced load will be less +than in other engines. It should be observed, however, that this +statement is apparently not borne out by experiments which the author +has had occasion to make. To a slight degree, this economy is obtained +at the cost of simplicity, and consequently, at the cost of the engine. +At all events, the engines have the merit of great cyclic regularity, +rendering them serviceable for driving electric-light dynamos; but this +regularity can also be attained by the use of the extra heavy fly-wheels +which English firms, in particular, have introduced. + +=Automatic Starting.=--When the gas-engine was first introduced, +starting was effected simply by manually turning the fly-wheel until +steady running was assured. This procedure, altogether too crude in its +way, is attended with some danger. In a few countries it is prohibited +by laws regulating the employment of industrial machinery. If the engine +be of rather large size one, moreover, which operates at high +pressure--such a method of starting is very troublesome. For these +reasons, among others, manufacturers have devised automatic means of +setting a gas-engine in motion. + +Of such automatic devices, the first that shall be mentioned is a +combination of pipes, provided with cocks, by the manipulation of which, +a certain amount of gas, drawn from the supply pipe, is introduced into +the engine-cylinder. The piston is first placed in a suitable position, +and behind it a mixture is formed which is ignited by a naked flame +situated near a convenient orifice. When the explosion takes place the +ignition-orifice is automatically closed, and the piston is given its +motive impulse. The engine thus started continues to run in accordance +with the regular recurrence of the cycles. In this system, starting is +effected by the explosion of a mixture, without previous compression. + +Some designers have devised a system of hand-pumps which compress in the +cylinder a mixture of air and gas, ignited at the proper time by +allowing it to come into contact with the igniter, through the +manipulation of cocks (Fig. 39). + +These two methods are not absolutely effective. They require a certain +deftness which can be acquired only after some practice. Furthermore, +they are objectionable because the starting is effected too violently, +and because the instantaneous explosion subjects the stationary piston, +crank, and fly-wheel to a shock so sudden that they may be severely +strained and may even break. Moreover, the slightest leakage in one of +the valves or checks may cause the entire system to fail, and, +particularly in the case of the pump, may induce a back explosion +exceedingly dangerous to the man in charge of the engine. + +These systems are now almost generally supplanted by the compressed-air +system, which is simpler, less dangerous, and more certain in its +effect. + +The elements comprising the system in question include essentially a +reservoir of thick sheet iron, capable of resisting a pressure of 180 to +225 pounds and sufficient in capacity to start an engine several times. +This reservoir is connected with the engine by piping, which is disposed +in one of two ways, depending upon whether the reservoir is charged by +the engine itself operatively connected with the compressor, or by an +independent compressor, mechanically operated. + +[Illustration: FIG. 39.--Tangye starter.] + +In the first case, the pipe is provided with a stop-cock, mounted +adjacent to the cylinder, and with a check-valve. When the engine is +started and the gas cut off, the air is drawn in at each cycle and +driven back into the reservoir during the period of compression. When +the engine, running under these conditions by reason of the inertia of +the fly-wheel, begins to slow down, the check-valve is closed and the +gas-admission valve opened, so as to produce several explosions and to +impart a certain speed to the engine in order to continue the charging +of the reservoir with compressed air. This done, the valve on the +reservoir itself is tightly closed, as well as the check-valve, so as to +avoid any leakage likely to cause a fall in the reservoir's pressure. + +In the second case, which applies particularly to engines of more than +50 horse-power, the charging pipe connected with the reservoir is +necessarily independent of the pipe by means of which the motor is +started. The reservoir having been filled and the decompression cam +thrown into gear, starting is accomplished: + +1. By placing the piston in starting position, which corresponds with a +crank inclination of 10 to 20 degrees in the direction of the piston's +movement, from the rear dead center, immediately after the period of +compression; + +2. By opening the reservoir-valve; + +3. By allowing the compressed air to enter the cylinder rapidly, through +the quick manipulation of the stop-cock, which is closed again when the +impulse is given and reopened at the corresponding period of the +following cycle, this operation being repeated several times in order to +impart sufficient speed to the motor; + +4. By opening the gas-valve and finally closing the two valves of the +compressed-air pipe. + +The pipes and compressed-air reservoirs should be perfectly tight. The +reservoirs should have a capacity in inverse ratio to the pressure under +which they are placed, _i.e._, they increase in size as the pressure +decreases. If, for example, the reservoirs should be operated normally +at a pressure of 105 to 120 pounds per square inch, their capacity +should be at least five or six times the volume of the engine-cylinder. +If these reservoirs are charged by the engine itself, the pressure will +always be less by 15 to 20 per cent. than that of the compression. + + + + + CHAPTER III + + THE INSTALLATION OF AN ENGINE + + +In the preceding chapter the various structural details of an engine +have been summarized and those arrangements indicated which, from a +general standpoint, seem most commendable. No particular system has been +described in order that this manual might be kept within proper limits. +Moreover, the best-known writers, such as Hutton, Hiscox, Parsell and +Weed, in America; Aime Witz, in France; Dugald Clerk, Frederick Grover, +and the late Bryan Donkin, in England; Gueldner, Schottler, Thering, in +Germany, have published very full descriptive works on the various types +of engines. + +We shall now consider the various methods which seem preferable in +installing an engine. The directions to be given, the author believes, +have not been hitherto published in any work, and are here formulated, +after an experience of fifteen years, acquired in testing over 400 +engines of all kinds, and in studying the methods of the leading +gas-engine-building firms in the chief industrial centers of Europe and +America. + +=Location.=--The engine should be preferably located in a well-lighted +place, accessible for inspection and maintenance, and should be kept +entirely free from dust. As a general rule, the engine space should be +enclosed. An engine should not be located in a cellar, on a damp floor, +or in badly illuminated and ventilated places. + +=Gas-Pipes.=--The pipes by which fuel is conducted to engines, driven by +street-gas, and the gas-bags, etc., are rarely altogether free from +leakage. For this reason, the engine-room should be as well ventilated +as possible in the interest of safety. Long lines of pipe between the +meter and the engine should be avoided, for the sake of economy, since +the chances for leakage increase with the length of the pipe. It seldom +happens that the leakage of a pipe 30 to 50 feet long, supplying a 30 +horse-power engine, is much less than 90 cubic feet per hour. The +beneficial effect of short supply pipes between meter and engine on the +running of the engine is another point to be kept in mind. + +An engine should be supplied with gas as cool as possible, which +condition is seldom realized if long pipe lines be employed, extending +through workshops, the temperature of which is usually higher than that +of underground piping. On the other hand, pipes should not be exposed to +the freezing temperature of winter, since the frost formed within the +pipe, and particularly the crystalline deposition of naphthaline, +reduces the cross section and sometimes clogs the passage. Often it +happens that water condenses in the pipes; consequently, the piping +should be disposed so as to obviate inclines, in which the water can +collect in pockets. An accumulation of water is usually manifested by +fluctuations in the flame of the burner. In places where water can +collect, a drain-cock should be inserted. In places exposed to frost, a +cock or a plug should be provided, so that a liquid can be introduced to +dissolve the naphthaline. To insure the perfect operation of the engine, +as well as to avoid fluctuations in nearby lights, pipes having a large +diameter should preferably be employed. The cross-section should not be +less than that of the discharge-pipe of the meter, selected in +accordance with the prescriptions of the following table: + + GAS-METERS. + + Table Headings-- + Column A: Capacity. + Column B: Normal hourly flow. + Column C: Height. + Column D: Width. + Column E: Depth. + Column F: Diameter of pipe. + Column G: Power of engine to be fed. + _________________________________________________________________ + | | | + | | Dimension in inches. | + | |_______________________________________| + | | | | | | + A. | B. | C. | D. | E. | F. | G. + ________|_________|_________|__________|__________|_______|______ + | | | | | | + burners | cu. ft. | | | | | h.-p. + 3 | 14.726 | 13 | 11 | 9-13/16 | 0.590 | 1/2 + 5 | 24.710 | 18 | 13-3/4 | 10-5/8 | 0.787 | 3/4 + 10 | 49.420 | 21-1/4 | 18-1/2 | 12-9/16 | 0.984 | 1-2 + 20 | 98.840 | 23-3/16 | 19-11/16 | 15-5/16 | 1.181 | 3-4 + 30 | 148.260 | 25-5/8 | 21-11/16 | 18-3/16 | 1.456 | 5-6 + 50 | 247.100 | 29-1/2 | 24-5/16 | 20-7/16 | 1.592 | 7-10 + 60 | 296.520 | 30-5/16 | 25-5/8 | 25-5/8 | 1.671 | 11-14 + 80 | 395.360 | 33-5/16 | 30-5/16 | 27-1/8 | 1.968 | 15-19 + 100 | 494.200 | 35 | 33-7/16 | 29-15/16 | 1.968 | 20-25 + 150 | 741.300 | 40-3/16 | 40-3/16 | 33-13/16 | | 30-40 + ________|_________|_________|__________|__________|_______|______ + +The records made are exact only when the meters (Fig. 40) are installed +and operated under normal conditions. Two chief causes tend to falsify +the measurements in wet meters: (1) evaporation of the water, (2) the +failure to have the meter level. + +Evaporation occurs incessantly, owing to the flowing of the gas through +the apparatus, and increases with a rise in the temperature of the +atmosphere surrounding the meter. Consequently this temperature must be +kept down, for which reason the meter should be placed as near the +ground as possible. The evaporation also increases with the volume of +gas delivered. Hence the meter should not supply more than the volume +for which it was intended. In order to facilitate the return of the +water of condensation to the meter and to prevent its accumulation, the +pipes should be inclined as far as possible toward the meter. The +lowering of the water-level in the meter benefits the consumer at the +expense of the gas company. + +[Illustration: FIG. 40.--Wet gas-meter.] + +Inclination from the horizontal has an effect that varies with the +direction of inclination. If the meter be inclined forward, or from left +to right, the water can flow out by the lateral opening at the level, +and incorrect measurements are made to the consumer's cost. + +During winter, the meter should be protected from cold. The simplest way +to accomplish this, is to wrap substances around the meter which are +poor conductors of heat, such as straw, hay, rags, cotton, and the like. +Freezing of the water can also be prevented by the addition of alcohol +in the proportion of 2 pints per burner. The water is thus enabled to +withstand a temperature of about 5 degrees F. below zero. Instead of +alcohol, glycerine in the same proportions can be employed, care being +taken that the glycerine is neutral, in order that the meter may not be +attacked by the acids which the liquid sometimes contains. + +[Illustration: FIG. 41.--Dry gas-meter.] + +=Dry Meters.=--Dry meters are employed chiefly in cold climates, where +wet meters could be protected only with difficulty and where the water +is likely to freeze. In the United States the dry meter is the type most +widely employed. In Sweden and in Holland it is also generally +introduced (Fig. 41). + +In the matter of accuracy of measurement there is little, if any, +difference between wet and dry meters. The dry meter has the merit of +measuring correctly regardless of the fluctuations in the water level. +On the other hand, it is open to the objection of absorbing somewhat +more pressure than the wet meter, after having been in operation for a +certain length of time. This is an objection of no great weight; for +there is always enough pressure in the mains and pipes to operate a +meter. + +[Illustration: FIG. 42.--Section through a dry gas-meter.] + +In many cases, where the employment of non-freezing liquids is +necessary, the dry meter may be used to advantage, since all such +liquids have more or less corroding effect on sheet lead and even tin, +depending upon the composition of the gas. + +[Illustration: FIG. 43.--Section through a dry gas-meter.] + +The dry meter comprises two bellows, operating in a casing divided into +two compartments by a central partition. The gas is distributed on one +or the other side of the bellows, by slides _B_. The slides _B_ are +provided with cranks _E_, controlled by levers _M_, actuated by +transmission shafts _O_, driven by the bellows. The meter is adjusted by +a screw which changes the throw of the cranks _E_ and consequently +affects the bellows. The movement of the crank-shaft _D_ is transmitted +to the indicating apparatus. In order to obviate any leakage, this shaft +passes through a stuffing-box, _G_. The diagrams (Figs. 42-43) show the +construction of a dry meter, the arrows indicating the course taken by +the gas. + +[Illustration: FIG. 44.--Rubber bag to prevent fluctuations of the +ignition flame.] + +[Illustration: FIG. 45.--Rubber bags on gas-pipes.] + +Care should be taken to provide the gas-pipe with a drain-cock, at a +point near the engine. By means of this cock, any air in the pipe can be +allowed to escape before starting; otherwise the engine can be set in +motion only with difficulty. If the engine be provided with an +incandescent tube, the gas-supply pipe of the igniter should be fitted +with a small rubber pouch or bag, in order to obviate fluctuations in +the burner flame, caused by variations in the pressure (Fig. 44). As a +general rule, the supply-pipe should be connected with the main pipe on +the forward side of the bags and gas-governors. The main pipe and all +other piping near the engine should extend underground, so that free +access to the motor from all sides can be obtained, without possibility +of injury. + +=Anti-pulsators, Bags, Pressure-Regulators.=--The most commonly employed +means of preventing fluctuation of nearby lights, due to the sharp +strokes of the engine, consists in providing the gas-supply pipe with +rubber bags (Fig. 45), which form reservoirs for the gas and, by reason +of their elasticity, counteract the effect produced by the suction of +the engine. Nevertheless, in order to insure a supply of gas at a +constant pressure, which is necessary for the perfect operation of the +engine, there are generally used, in addition to the bags, devices +called gas-governors, or anti-pulsators (Fig. 46). + +Although these devices are constructed in different ways, the underlying +principle is the same in all. They comprise a metallic casing, +containing a flexible diaphragm of rubber or of some fabric impermeable +to gas. Suction of the engine creates a vacuum in the casing. The +diaphragm bends, thereby actuating a valve, which cuts off the gas +supply. During the three following periods (compression, explosion, and +exhaust) the gas, by reason of its pressure on the diaphragm, opens the +valve and fills the casing, ready for the next suction stroke. + +[Illustration: FIG. 46.--An anti-pulsator.] + +Other devices, which are never sold with the engine, but are rendered +necessary by reason of the conditions imposed by the gas supply are sold +under the name "pressure-regulators" (Fig. 47). They consist of a bell, +floating in a reservoir containing water and glycerine (or mercury), and +likewise actuate a valve which partially controls the flow of gas. This +valve being balanced, its mechanical action is the more certain. Such +devices are very effective in maintaining the steadiness of lights. On +the other hand, they are often an obstacle to the operation of the +engine because they reduce the flow and pressure of the gas too much. In +order to obviate this difficulty, a pressure-regulator should be chosen +with discrimination, and of sufficiently large size to insure the +maintenance of an adequate supply of gas to the engine. Frequent +examinations should be made to ascertain if the bell of the regulator is +immersed in the liquid. In the case of anti-pulsators, care should be +taken that they are not spattered with oil, which has a disastrous +effect on rubber. Anti-pulsators are generally mounted about 4 inches +from a wall, in order that the diaphragm may be actuated by hand, if +need be. + +[Illustration: FIG. 47.--A pressure-regulator.] + +=Precautions.=--In order not to strain the rubber of the bags or of the +anti-pulsators, it is advisable to place a stop-cock in advance of these +devices so that they can not be filled while the motor is at rest. + +The capacity of the rubber bags that can be bought in the market being +limited, it is necessary to place one, two, or three extra bags in +series (Figs. 48 and 49), for large pipes; but it should be borne in +mind that the total section of the branch pipes should be at least equal +to that of the main pipe. It is also advisable to extend the tube +completely through the bag as shown in Figs. 48 and 49. + +[Illustration: FIGS. 48-49.--Arrangement of rubber bags.] + +If there be two branch pipes the minimum diameter which meets this +requirement is ascertained as follows: Draw to any scale a semicircle +having a diameter equal or proportional to that of the main pipe (Fig. +50). The sides of the isosceles triangle inscribed within this +semicircle give the minimum diameter of each of the branch pipes. + +Sometimes engines are provided with a cock having an arrangement by +means of which the gas feed is permanently regulated, according to the +quality and pressure of the gas and according to the load at which the +engine is to run. This renders it possible to open the cock always to +the same point (Fig. 51). + +[Illustration: FIG. 50.] + +[Illustration: FIG. 51.] + +=Air Suction.=--In a special chapter the precautions to be taken to +counteract the influence of the suction of the engine in causing +vibration will be treated. The manner in which the suction of air is +effected necessarily has as marked an influence on the operation of the +engine as the supply of gas, since air and gas constitute the explosive +mixture. + +Resistance to the suction of air should be carefully avoided, for which +reason the length of the pipe should be reduced to a minimum, and its +cross-section kept at least equal to that of the air inlet of the +engine. Since the quality of street-gas varies with each city, the +proper proportions of gas and air are not constant. In order that these +proportions may be regulated, it is a matter of some importance to fit +some suitable device on the pipe. Good engines are provided with a plug +or flap valve. Generally the air-pipe terminates either in the hollowed +portion of the frame, or in an independent pot, or air chest. The first +arrangement is not to be recommended for engines over 20 to 25 +horse-power. Accidents may result, such as the breaking of the frame by +reason of back firing, of which more will be said later. If an +independent chest be employed, its closeness to the ground renders it +possible for dust easily to pass through the air-holes in the walls at +the moment of suction, and even to enter the cylinder, where its +presence is particularly harmful, leading, as it does, to the rapid wear +of the rubbing surfaces. This evil can be largely remedied by filling +the air-chest with cocoa fiber or even wood fiber, provided the latter +does not become packed down so as to prevent the air from passing +freely. Such fibers act as air-filters. Regular cleaning or renewal of +the fiber protects the cylinder from wear. In a general way, care should +be taken, before fitting both the gas and air pipes, to tap the pipes, +elbows, and joints lightly with a hammer on the outside in order to +loosen whatever rust or sand may cling to the interior; otherwise this +foreign matter may enter the cylinder and cause perturbations in the +operation of the engine. Under all circumstances, care should be taken +not to place the end of the air-pipe under the floor or in an enclosed +space, because leakage may occur, due to the bad seating of the +air-valve, thereby producing a mixture which may explode if the flame +leaps back, as we shall see in the discussion of suction by pipes +terminating in the hollow of the frame. On the other hand, sand or +sawdust should not be sprinkled on the floor. + +=Exhaust.=--For the exhaust, cast-iron or drawn pipes as short as +possible should be used. Not only the power of the engine, but also its +economic consumption, can be markedly affected by the employment of long +and bent pipes. Resistance to the exhaust of the products of combustion +not only causes an injurious counter-pressure, but also prevents the +clearing of the cylinder of burnt gases, which contaminate the aspired +mixture and rob it of much of its explosiveness. The necessity of +evacuating the cylinder as completely as possible is, nevertheless, not +always reconcilable with local surroundings. To a certain extent, the +objections to long exhaust-pipes are overcome by rigorously avoiding the +use of elbows. Gradual curves are preferable. In the case of very long +pipes it is advisable to increase their diameter every 16 feet from the +exhaust. The exhaust-chest should be placed as near as possible to the +engine; it should never be buried; for the joints of the inlet and +outlet pipes of the exhaust-chest should be easily accessible, so that +they may be renewed when necessary. The author recommends the placing +of the exhaust-chest in a masonry pit, which can be closed with a +sheet-metal cover. For engines of 20 horse-power and upward, these +joints should be entirely of asbestos. Pipes screwed directly into the +casting are liable to rust. Exposed as they are to the steam or water of +the exhaust, they cannot be detached. + +[Illustration: FIG. 52.--Method of mounting pipes.] + +The water, which results from the combination of the hydrogen of the gas +with the oxygen of the air, is deposited in most cases at the bottom of +the exhaust-chest. It is advisable to fit a plug or iron cock in the +base of the chest. Alkaline or acid water will always corrode a bronze +cock. In order that the pipes may not also be attacked, they are not +disposed horizontally, but are given a slight incline toward the point +where the water is drained off. If pipes of some length be employed, +they should be able to expand freely without straining the joints, as +shown in the accompanying diagram (Fig. 52), in which the exhaust-chest +rests on iron rollers which permit a slight displacement. + +For the sake of safety, at least that portion of the piping which is +near the engine should be located at a proper distance from woodwork and +other combustible material. By no means should the exhaust discharge +into a sewer or chimney, even though the sewer or chimney be not in use; +for the unburnt gases may be trapped, and dangerous explosions may ensue +at the moment of discharge. + +The joints or threaded sleeves employed in assembling the exhaust-pipe +should be tested for tightness. The combined action of the moisture and +heat causes the metal to rust and to deteriorate very rapidly at leaky +spots. + +When several engines are installed near one another, each should be +provided with a special exhaust-pipe; otherwise it may happen, when the +engines are all running at once, that the products of combustion +discharged by the one may cause a back pressure detrimental to the +exhaust of the next. + +It is possible to employ a pipe common to all the exhausts if the pipe +starts from a point beyond the exhaust-chests, in which case Y-joints +and not T-joints are to be used. + +The manner of securing the pipes to walls by means of detachable +hangers, lined with asbestos, is shown in a general way in the +accompanying Fig. 53. The object of this arrangement is to render +detachment easy and to prevent the transmission of shocks to the +masonry. + +The precautions to be taken for muffling the noise of the exhaust will +be discussed later. + +The end of the exhaust-pipe should be slightly curved down in order to +prevent the entrance of rain. Exhaust-pipes are subjected to +considerable vibration, due to the sudden discharge of the gases. To +protect the joints, the pipes should be rigidly fastened in place. + +[Illustration: FIG. 53.--Method of securing pipes to walls.] + +=Legal Authorization.=--In most countries gas-engines may be installed +only in accordance with the provision of general or local laws, which +impose certain conditions. These laws vary with different localities, +for which reason they are not discussed here. + + + + + CHAPTER IV + + FOUNDATION AND EXHAUST + + +The reader will remember from what has already been said that a +gas-engine is a motor which, more than any other, is subjected to +forces, suddenly and repeatedly exerted, producing violent reactions on +the foundation. It follows that the foundation must be made particularly +resistant by properly determining its shape and size and by carefully +selecting the material of which it is to be built. + +=The Foundation Materials.=--Well-hardened brick should be used. The top +course of bricks should be laid on edge. It is advisable to increase the +stability of the foundation by longitudinally elongating it toward the +base, as shown in the accompanying diagram (Fig. 54). + +As a binding material, only mortar composed of coarse sand or river sand +and of good cement, should be used. Instead of coarse sand, crushed +slag, well-screened, may be employed. The mortar should consist of 2/3 +slag and 1/3 cement. Oil should not in any way come into contact with +the mortar; it may percolate through the cement and alter its resistant +qualities. + +As in the construction of all foundations, care should be taken to +excavate down to good soil and to line the bottom with concrete, in +order to form a single mass of artificial stone. A day or two should be +allowed for the masonry to dry out, before filling in around it. + +When the engine is installed on the ground floor above a vaulted cellar, +the foundation should not rest directly on the vault below or on the +joists, but should be built upon the very floor of the cellar, so that +it passes through the planking of the ground floor without contact. + +[Illustration: FIG. 54.--Method of building the foundation.] + +When the engine is to be installed on a staging, the method of securing +it in place illustrated in Fig. 55 should be adopted. + +Although a foundation, built in the manner described, will fulfill the +usual conditions of an industrial installation, it will be inadequate +for special cases in which trepidation is to be expected. Such is the +case when engines are to be installed in places where, owing to the +absence of factories, it is necessary to avoid all nuisance, such as +noise, trepidations, odors, and the like. + +[Illustration: FIG. 55.--Elevated foundation.] + +=Vibration.=--In order to prevent the transmission of vibration, the +foundation should be carefully insulated from all neighboring walls. For +this purpose various insulating substances called "anti-vibratory" are +to be recommended. Among these may be mentioned horsehair, felt packing, +cork, and the like. The efficacy of these substances depends much on the +manner in which they are applied. It is always advisable to interpose a +layer of one of these substances, from one to four inches thick, between +the foundation and the surrounding soil, the thickness varying with the +nature of the material used and the effect to be obtained. Between the +bed of concrete, mentioned previously, and the foundation-masonry and +between the foundation and the engine-frame, a layer of insulating +material may well be placed. Preference is to be given to substances not +likely to rot or at least not likely to lose their insulating property, +when acted upon by heat, moisture or pressure. + +Here it may not be amiss to warn against the utilization of cork for the +bottom of the foundation; for water may cause the cork to swell and to +dislocate the foundation or destroy its level. + +The employment of the various substances mentioned does not entail any +great expense when the foundations are not large and the engines are +light. But the cost becomes considerable when insulating material is to +be employed for the foundation of a 30 to 50 horse-power engine and +upwards. For an engine of such size the author recommends an arrangement +as simple as it is efficient, which consists in placing the foundation +of the engine in a veritable masonry basin, the bottom of which is a bed +of concrete of suitable thickness. The foundation is so placed that the +lateral surfaces are absolutely independent of the supporting-walls of +the basin thus formed. Care should be taken to cover the bottom with a +layer of dry sand, rammed down well, varying in thickness with each +case. This layer of sand constitutes the anti-vibratory material and +confines the trepidations of the engine to the foundation. + +As a result of this arrangement, it should be observed that, being +unsupported laterally, the foundation should be all the more resistant, +for which reason the base-area and weight should be increased by 30 to +40 per cent. The expense entailed will be largely offset by saving the +cost of special anti-vibratory substances. In places liable to be +flooded by water, the basin should be cemented or asphalted. + +When the engine is of some size and is intended for the driving of one +or more dynamos which may themselves give rise to vibrations, the +dynamos are secured directly to the foundation of the engine, which is +extended for that purpose, so that both machines are carried solidly on +a single base. + +The foregoing outline should not lead the proprietor of a plant to +dispense with the services of experts, whose long experience has brought +home to them the difficulties to be overcome in special cases. + +It should here be stated, as a general rule, that the bricks should be +thoroughly moistened before they are laid in order that they may grip +the mortar. + +After having been placed on the foundation and roughly trimmed with +respect to the transmission devices, the engine is carefully leveled by +means of hardwood wedges driven under the base. This done, the bolts are +sealed by very gradually pouring a cement wash into the holes, and +allowing it to set. When the holes are completely filled and the bolts +securely fastened in place, a shallow rim, or edge of clay, or sand is +run around the cast base, so as to form a small box or trough, in which +cement is also poured for the purpose of firmly binding the engine frame +and foundation together. When, as in the case of electric-light engines, +single extra-heavy fly-wheels are employed, provided with bearings held +in independent cast supports, the following rule should be observed to +prevent the overheating due to unlevelness, which usually occurs at the +bushings of these bearings: That part of the foundation which is to +receive such a support should rest directly on the concrete bed and +should be rigidly connected at the bottom with the main foundation. When +the foundation is completely blocked up, the fly-wheel bearing with its +support is hung to the crank-shaft; and not until this is effected is +the masonry at the base of the support completed and rigidly fixed in +its proper position. + +For very large engines, the foundation-bolts should be particularly well +sealed into the foundation. In order to attain this end the bricks are +laid around the bolt-holes, alternately projected and retracted as shown +in Fig. 54. Broken stone is then rammed down around the fixed bolt; in +the interstices cement wash is poured. + +=Air Vibration, etc.=--Vibration due chiefly to the transmission of +noises and the displacement of air by the piston should not be confused +with the trepidations previously mentioned. + +The noise of an engine is caused by two distinct phenomena. The one is +due to the transmitting properties of the entire solid mass constituting +the frame, the foundation, and the soil. The other is due to vibrations +transmitted to the air. In both cases, in order to reduce the noise to a +minimum, the moving parts should be kept nicely adjusted, and above all, +shocks avoided, the more harmful of which are caused by the play between +the joint at the foot of the connecting-rod and the piston-pin, and +between the head of the connecting-rod and the crank-shaft. + +Although smooth running of the engine may be assured, there is always an +inherent drawback in the rapid reciprocating movement of the piston. In +large, single-acting gas-engines, a considerable displacement of air is +thus produced. In the case of a forty horse-power engine having a +cylinder diameter and piston-stroke respectively of 13-3/4 inches and +21-3/5 inches, it is evident that at each stroke the piston will +displace about 2 cubic feet of air, the effect of which will be doubled +when it is considered that on the forward stroke back pressure is +created and on the return stroke suction is produced. + +The air motion caused by the engine is the more readily felt as the +engine-room is smaller. If the room, for example, be 9 feet by 15 feet +by 8 feet, the volume will be 1,080 cubic feet. From this it follows +that the 2 cubic feet of air in the case supposed will be alternately +displaced six times each second, which means the displacement of 12 +cubic feet at short intervals with an average speed of 550 feet per +minute. Such vibrations transmitted to halls or neighboring rooms are +due entirely to the displacement of the air. + +In installations where the air-intake of the engine is located in the +engine-room, a certain compensation is secured, at the period of +suction, between the quantity of air expelled on the forward stroke of +the piston and the quantity of air drawn into the cylinder. From this it +follows that the vibration caused by the movement of the air is felt +less and occurs but once for two revolutions of the engine. + +This phenomenon is very manifest in narrow rooms in which the engine +happens to be installed near glass windows. By reason of the elasticity +of the glass, the windows acquire a vibratory movement corresponding in +period with half the number of revolutions of the engine. It follows +from the preceding that, in order to do away with the air vibration +occasioned by the piston in drawing in and forcing out air in an +enclosed space, openings should be provided for the entrance of large +quantities of air, or a sufficient supply of air should be forced in by +means of a fan. + +The author ends this section with the advice that all pipes in general +and the exhaust-pipe in particular be insulated from the foundation and +from the walls through which they pass as well as from the ground, as +metal pipes are good conductors of sound and liable to carry to some +distance from the engine the sounds of the moving parts. + +=Exhaust Noises.=--Among the most difficult noises to muffle is that of +the exhaust. Indeed, it is the exhaust above all that betrays the +gas-engine by its discharge to the exterior through the exhaust-pipe. +The most commonly employed means for rendering the exhaust less +perceptible consists in extending the pipe upward as far as possible, +even to the height of the roof. This is an easy way out of the +difficulty; but it has a bad effect on the operation of the engine. It +reduces the power generated and increases the consumption, as will be +explained in a special paragraph. + +Expansion-boxes, more commonly called exhaust-mufflers, considerably +deaden the noise of explosion by the use of two or three successive +receptacles. But this remedy is attended with the same faults that mark +the use of extremely long pipes. The best plan is to mount a single +exhaust-muffler near the discharge of the engine in the engine-room +itself, where it will serve at least the purpose of localizing the +sound. + +[Illustration: FIG. 56.--Exhaust-muffler.] + +The employment of pipes of sufficiently large cross-section to +constitute expansion-boxes in themselves will also muffle the exhaust. A +more complete solution of the problem is obtained by causing the +exhaust-pipe, after leaving the muffler, to discharge into a masonry +trough having a volume equal to twelve times that of the engine-cylinder +(Fig. 56). This trough should be divided into two parts, separated by a +horizontal iron grating. Into the lower part, which is empty, the +exhaust-pipe discharges; in the upper part, paving-blocks or hard stones +not likely to crumble with the heat, are placed. Between this layer of +stones and the cover it is advisable to leave a space equal to the +first. Here the gases may expand after having been divided into many +parts in passing through the spaces left between adjacent stones. The +trough should not be closed by a rigid cover; for, although efficient +muffling may be attained, certain disadvantages are nevertheless +encountered. It may happen that in a badly regulated engine, unburnt +gases may be discharged into this trough, forming an explosive mixture +which will be ignited by the next explosion, causing considerable +damage. Still, the explosion will be less dangerous than noisy. It may +be mentioned in passing that this disadvantage occurs rarely. + +A second arrangement consists in superposing the end of the exhaust-pipe +upon a casing of suitable size, which casing is partitioned off by +several perforated baffle-plates. This casing is preferably made of +wood, lined with metal, so that it will not be resonant. The size of the +casing, the number of partitions and their perforations, and the manner +of disposing the partitions have much to do with the result to be +obtained. Here again the experience of the expert is of use. + +Various other systems are employed, depending upon the particular +circumstances of each case. Among these systems may be mentioned those +in which the pipe is forked at its end to form either a yoke (Fig. 57) +or a double curve, each branch of which terminates in a muffler (Fig. +58). + +[Illustration: FIG. 57.] + +[Illustration: FIG. 58.--Two types of exhaust-mufflers.] + +It should be observed that, under ordinary conditions, noises heard as +hissing sounds are often due to the presence of projections, or to +distortion of the pipes near the discharge opening. Consequently, in +connecting the pipes, care should be taken that the joints or seams have +no interior projections. Occasionally, water may be injected into the +exhaust-muffler in order to condense the vapors of the exhaust, the +result being a deadening of the noises; but in order to be truly +efficient this method should be employed with discretion, for which +reason the advice of an expert is of value. + + + + + CHAPTER V + + WATER CIRCULATION + + +Circulation of water in explosion-engines is one of the essentials of +their perfect operation. Two special cases are encountered. In the one +the jacket of the engine is supplied with running water; in the other, +reservoirs are employed, the circulation being effected simply by the +difference in specific gravity in a thermo-siphon apparatus. Coolers are +also used. + +=Running Water.=--A water-jacket fed from a constant source of running +water, such as the water mains of a town, is certainly productive of the +best results, the supply, moreover, being easily regulated; but the +system is not widely used because the water runs away and is entirely +lost. If running water be employed, the outlet of the jacket is so +disposed that the water gushes out immediately on leaving the cylinder, +and that the flow is visible and accessible, in order that the +temperature may be tested by the hand. Apart from the relatively great +cost of water in towns, the use of running water is objectionable on +account of its chemical composition. Though it may be clear and limpid, +it frequently contains lime salts, carbonates, sulphates, and silicates +which are precipitated by reason of the sudden change of temperature to +which the water is subjected as it comes into contact with the walls of +the cylinder. That part of the water-jacket surrounding the head or +explosion-chamber, where the temperature is necessarily the highest, +becomes literally covered with calcareous incrustations, which are the +more harmful because they are bad conductors of heat and because they +reduce and even obstruct the passage exactly at the point where the +water must circulate most freely to do any good. If the circulating +water be pumped into the jacket, it is preferable, wherever possible, to +use cistern water, which is not likely to contain lime salts in +suspension. If river water be used, it should be free from the +objections already mentioned, which are all the more grave if the water +be muddy, as sometimes happens. The water-jacket can be easily freed +from all non-adhering deposits by flushing it periodically through the +medium of a conveniently placed cock. It is always preferable to pass +the water through a reservoir where its impurities can settle, before it +flows to the cylinder. In the case considered, the water usually has an +average temperature of 54 to 60 degrees F., under which condition the +hourly flow should be at least 5-1/2 gallons per horse-power per hour, +the temperature rising at the outlet-pipe of the cylinder to 140 and 158 +degrees F., which should not be surpassed. However, in engines working +with high compression, 104 to 122 degrees F. should not be exceeded. + +If the water-jacket be fed by a reservoir, it is essential that the +reservoir comply with the following conditions: + +In horizontal engines the water-inlet is always located in the base of +the cylinder, while the outlet is located at the top. By providing the +inlet-pipe extending to the cylinder with a cock, the circulation of +water can be regulated to correspond with the work performed by the +engine. Another cock at the end of the outlet-pipe near the reservoir +serves, in conjunction with the first, to arrest the circulating water. +When the weather is very cold or when the cylinder must be repaired, +these two cocks may be closed, and the pipe and water-jacket of the +cylinder drained by means of the drain-cock _V_ (Fig. 59), mounted at +the inlet of the engine's water-jacket. In order that the pressure of +the atmosphere may not prevent the flowing of the water, the highest +part of the pipe is provided with a small tube, _T_, communicating with +the atmosphere. + +[Illustration: FIG. 59.--Thermo-siphon cooling system.] + +On account of the importance of preventing losses of the charge in the +pipes the author recommends the utilization of sluice-valves of the type +shown in Fig. 60, instead of the usual cone or plug type. + +[Illustration: FIG. 60.--Vanne sluice-cock.] + +=Water-Tanks.=--The reservoir is mounted in such a way that its base is +flush with the top of the cylinder; it should be as near as possible to +the cylinder in order to obviate the use of long inlet and return pipes. +This fact, however, does not necessarily render it advisable to place +the reservoir in the engine-room; for such a disposition is doubly +disadvantageous in so far as it does not permit a sufficiently rapid +cooling of the circulating water by reason of the high temperature of +the surrounding air, and in so far as it is liable to cause the +formation of vapors which injuriously affect the engine. Consequently, +the reservoir should be placed in as cool a place as possible, +preferably even in the open air; for the water is not likely to freeze, +except when it has been allowed to stand for a considerable time. The +reservoir should be left uncovered so as to facilitate cooling by the +liberation of the vapors formed on the surface of the water. + +Circulation being effected solely by the difference in specific gravity +or density between the warmer water emerging from the cylinder and the +cooler water which flows in from the reservoir, the slightest +obstruction will impede the flow. Hence, the cross-section of the pipes +should not be less than that of the inlet and outlet openings of the +cylinder of the engine. Good circulation cannot be attained if the water +must overcome inclines or obstacles in the pipes themselves. Instead of +elbows, long curves of great radius, limited to the smallest possible +number, should be employed. This is particularly true of the return-pipe +extending from the cylinder back to the reservoir. For this pipe a +minimum incline of 10 to 15 per cent. should be allowed, in order that +the water may run up into the reservoir. The height of the water in the +reservoir should be from 2 to 4 inches above the discharge of the +return-pipe. In order to maintain this level it is advisable to use some +automatic device such as a float-valve, in which case the reservoir +should not be allowed to become too full. + +[Illustration: FIG. 61.--Correct arrangement of tanks and piping.] + +The size of a reservoir is determined by the engine; it should be large +enough to enable the engine to run smoothly at its maximum load for +several hours consecutively. Under these conditions, the reservoir +should have a capacity of 45 to 55 gallons per horse-power for engines +with "hit-and-miss" admission, and 55 to 65 gallons for engines +controlled by variable admission. It is not advisable to employ +reservoirs having a capacity of more than 330 to 440 gallons, the usual +diameter being about 3 feet. + +[Illustration: FIG. 62.--Incorrect arrangement of tanks and piping.] + +If the power of the engine be such that several reservoirs are +necessary, then the reservoirs should be connected in such a manner that +the top of the first communicates with the bottom of the next and so +on, the first reservoir receiving the water as it comes from the +cylinder (Fig. 61). + +Intercommunication of the reservoirs by means of a common top tube (_a_) +is objectionable; and simultaneous intercommunication at top and bottom +(_a_ and _b_) is ineffective, so far as one of the reservoirs is +concerned (Fig. 62). + +[Illustration: FIG. 63.--Tanks connected by inclined pipes.] + +The reservoirs are true thermo-siphons. Consequently the water should be +methodically circulated; in other words, the hottest water, flowing from +the engine into the top of the first reservoir and having, for example, +a temperature of 104 degrees F., is cooled off to 86 degrees F. and +drops to the bottom of the reservoir, thence to be driven, at a +temperature sensibly equal to 86 degrees F., to the second reservoir, +where a further cooling of 18 degrees F. takes place. In passing on to +the following reservoirs the temperature is still further lowered, until +the water finally reaches its minimum temperature, after which it flows +back to the engine-cylinder. + +[Illustration: FIG. 64.--Circulating pump with by-pass.] + +In order to effect this cooling, the reservoirs can be connected in +several ways. The most common method, as shown in Fig. 63, consists in +connecting the reservoirs by oblique pipes. This is open to criticism, +however, since leakage occurs, caused by the employment of elbows which +retard the circulation. A less cumbrous and more efficient method of +connection consists in joining the reservoirs by a single pipe at the +top, as shown in Fig. 61; but care must be taken to extend this pipe at +the point of its entrance into the adjoining reservoir by means of a +downwardly projecting extension, or to fit its discharge-end with a box, +closed by a single partition, open at the bottom. + +In order to prevent incrustation of the water-jacket surrounding the +cylinder, a pound of soda per 17 cubic feet of the reservoir capacity is +monthly introduced, and the jacket flushed weekly by a cock conveniently +mounted near the cylinder (Fig. 59). The jacket is thus purged of +calcareous sediments, which are prevented by the soda from adhering to +the metal. The flushing-cock mentioned also serves to drain the +water-jacket of the cylinder in case of intense or persistent cold, +which would certainly freeze the water in the jacket, thereby cracking +the cylinder or the exposed pipes. + +In order to regulate the circulation of the water in accordance with the +work performed by the engine, a cock should be fitted to the water +supply pipe at a convenient place. + +In engines of large size, driven at full load for long periods, cooling +by natural circulation is often inadequate. In such cases, circulation +is quickened by a small rotary or reciprocating pump, driven from the +engine itself and fitted with a by-pass provided with a cock. This +arrangement permits the renewal of the natural thermo-siphon circulation +in case of accident to the pump (Fig. 64). + +[Illustration: FIG. 65.--Water-cooler in which tree branches are +employed.] + +=Coolers.=--The arrangement which is illustrated in Fig. 65, and which +has the merit of simplicity, will be found of service in cooling the +water. It comprises a tank _B_ surmounted by a set of trays _E_, formed +of frames to which iron rods are secured, spaced 1 to 2 feet apart, so +as to form superimposed series separated by 1-1/2 to 2-1/3 feet. On +these trays bundles of tree branches are placed. The cold water at the +bottom of the tank is forced by the pump _P_i into the water-jacket, +from which it emerges hot, and flows through the pipe _T_, which ends in +a sprinkler _G_, formed of communicating tubes and perforated with a +sufficient number of holes to enable the water to fall upon the trays in +many drops. Thus finely divided, the water falls from one tray to +another, retarded as it descends by the bundles of tree branches. It +finally reaches the tank in a very cold condition and is then ready to +be pumped to the engine. Birch branches are to be preferred on account +of their tenuity. + +Great care should be taken to cover the tank with a sheet-metal closure +in order to prevent twigs and foreign bodies from entering and from +being drawn into the pump. + +[Illustration: FIG. 66.--Fan-cooler.] + +In the following table the dimensions of an operative apparatus of this +kind are given,--an apparatus, moreover, that may be constructed of wood +or of iron:-- + + Table Headings-- + Column A: Horse-power. + Column B: Volume in cubic ft. + Column C: Base. + Column D: Height. + Column E: Height of tray-base. + Column F: Pump--Capacity in gals. per min. + ______________________________________________ + | | | | + | | Tank. | | + | |____________________| | + | | | | | + A. | B. | C. | D. | E. | F. + _____|_____|_____________|______|______|______ + | | | | | + 30 | 105 | 4.9' x 4.9' | 4.4' | 6.6' | 16.71 + 40 | 154 | 5.2' x 5.2' | 5.6' | 7.4' | 18.69 + 50 | 190 | 5.7' x 5.7' | 6.4' | 8.1' | 21.99 + 75 | 350 | 6.6' x 6.6' | 8.1' | 9.1' | 35.18 + 100 | 490 | 7.4' x 7.4' | 9.1' | 9.1' | 43.98 + _____|_____|_____________|______|______|______ + +In order that the water may not drop to one side, the base of the +apparatus should be made 10 to 12 inches less in width than the tank. + +The size of these apparatus may be considerably reduced by constructing +them in the form of closed chests, into the bottom of which air maybe +injected by means of fans in order to accelerate cooling (Fig. 66). + + + + + CHAPTER VI + + LUBRICATION + + +Lubrication is a subject that should be studied by every gas-engine +user. So far as the piston is concerned it is a matter of the utmost +importance. The piston does its work under very peculiar conditions. It +is driven at great linear velocities; and it is, moreover, subjected to +high temperatures which have nothing in common with good lubrication if +care be not exercised. + +The piston is the essential, vital element of an engine. Upon its +freedom from leakage depends the maintenance of a proper compression, +and, consequently, the production of power and economical consumption. +As it travels forward and as it recedes from the explosion-chamber, it +uncovers more and more of the frictional surface constituting the +interior wall of the cylinder. This surface, as a result, is regularly +brought into contact with the ignited, expanding gases after each +explosion. For this reason the oil which covers the wall is constantly +subjected to high temperatures, by which it is likely to be volatilized +and burned. Therefore, the first condition to be fulfilled in properly +lubricating the piston is a constant and regular supply of oil. + +=Quality of Oils.=--For cylinder lubrication only the very best oils +should be used; perfect lubrication is of such importance that cost +should not be considered. Besides, the surplus oil which is usually +caught in the drip-pan is by no means lost. After having been filtered +it can be used for lubricating the bearings of the crank, the cam-shaft, +and like parts. + +Cylinder-oil should be exceedingly pure, free from acids, and composed +of hydrocarbons that leave no residue after combustion. Only mineral +oils, therefore, are suitable for the purpose. Those oils should be +selected which, with a maximum of viscosity, are capable of withstanding +great heat without volatilizing or burning. The point at which a good +cylinder-oil ignites should not be lower than 535 degrees F. + +Whether an oil possesses this essential quality is easily enough +ascertained in practice without resorting to laboratory tests. All that +is necessary is to heat the oil in a metal vessel or a porcelain dish. +In order that the temperature may be uniform the vessel is shielded from +the direct flame by interposing a piece of sheet metal or a layer of dry +sand. As soon as gases begin to arise a lighted match is held over the +oil. When the gases are ignited the thermometer reading is taken, the +instrument being immersed in the oil. The temperature recorded is that +corresponding with the point of ignition. + +For cylinder lubrication American mineral oil is preferable to Russian +oil. The specific gravity should lie somewhere between .886 and .889 at +70 degrees F. Oil of this quality begins to evaporate at about 365 +degrees F. Ignition occurs at 535 degrees F. The point of complete +combustibility lies between 625 and 645 degrees F. Oil of this quality +solidifies at 39 or 41 degrees F. Its color is a reddish yellow with a +greenish fluorescence. Compared with water its degree of viscosity lies +between 11.5 and 12.5 at a temperature of 140 degrees F. + +Before lubricating other parts of the engine with oil that has been used +for the piston, heavy particles and foreign matter, such as dust, +bearing incrustations, and the like, should be filtered out. The +piston-pivot and the connecting-rod head are preferably lubricated with +fresh oil, because their constant movement renders inspection difficult +and the control of lubrication irksome. A good, industrial mineral oil +of usual market quality will be found satisfactory. In order to bring +home the importance of employing good cylinder-oil and of proper +lubrication the author can only state that in his personal experience he +has frequently detected losses varying from 10 to 15 per cent. in the +power developed by engines poorly lubricated. + +=Types of Lubricators.=--Among the more common apparatus employed for +automatically lubricating the cylinder, the author mentions an English +oiler of the type pictured in Fig. 67 which is driven simply by a belt +from the intermediary shaft, and which rotates the pulley _P_ secured on +the shaft _a_ of the apparatus, at a very slow speed. The shaft _a_ is +provided at its end with a small crank, from which a small iron arm _f_ +is suspended, which arm dips in the oil contained in the cup _G_ of the +oiler. When the shaft _a_ is turned this arm, as it sweeps through the +oil-bath, collects a certain quantity of oil which it deposits on the +collector _b_. From this spindle the oil passes through an outlet-pipe +opening into the bottom of the oiler, and thence to the cylinder. The +entire apparatus is closed by a cover _D_ which can be easily removed in +order to ascertain the quantity of oil still remaining in the apparatus. +Many other systems are utilized which, like the one that has been +described, enable the feed to be controlled. Often small force-pumps are +employed as cylinder-lubricators. Whatever may be the type selected, +preference should be given to that in which the feed is visible (Fig. +68). + +[Illustration: FIG. 67.--An automatic English oiler.] + +If the oil be fed under pressure the cylinder is more constantly +lubricated. Pressure-lubricators are nowadays widely used on large +engines. It is advisable to add a little salt to the water contained in +sight-feed lubricators so that the drop of oil is easily freed. + +These oil-pumps are provided with small check-valves at their outlets as +well as at the inlets of cylinders. In order that pressure-lubricators +may operate perfectly they should be regularly inspected and the +check-valves ground from time to time. + +The lubrication of the crank-shaft and of the two connecting-rod heads +should receive every attention. + +[Illustration: FIG. 68.--Sight-feed lubricating-pump.] + +[Illustration: FIG. 69.--Method of oiling the piston and end of the +connecting-rod.] + +Lubricating devices should be employed which, besides being efficient, +do not necessitate the stopping of the engine in order to oil the +bearings. The foot of the connecting-rod at the point where it is +pivoted to the piston is generally lubricated with cylinder-oil which is +supplied by a tube mounted in the proper place across the piston-wall +(Fig. 69). This arrangement may be adequate enough for small engines; +but it is not sufficiently sure for engines of considerable size. An +independent lubricating system should be employed, lubrication being +effected either by a splasher mounted in front of the cylinder or by a +lubricator secured to the connecting-rod by which the pivot is +lubricated through the medium of a small tube supplying special oil +(Fig. 21). The head of the connecting-rod where it meets the crank, must +also be carefully lubricated because of the important nature of the work +which it must perform, and because of the shocks to which it is +subjected at each explosion. For motors of high power the system which +seems to give most satisfactory results is that illustrated in Fig. 70. +The arrangement there shown consists of an annular vessel secured at one +side of the crank and turning concentrically on its axis; the vessel +being connected with a long tube extending into a channel formed in the +crank and discharging at the surface of the crank-pin within the bearing +at the head of the connecting-rod. An adjustable sight-feed lubricator +conducts the oil along a pipe to the vessel. Turning with the shaft, the +vessel retains the oil in the periphery so that the feed in the +previously mentioned channel in the connecting-rod head, is constant. + +[Illustration: FIG. 70.--Method of oiling the crank-shaft.] + +The main crank-shaft bearings are more easily lubricated. Among the +systems commonly used with good results may be mentioned that shown in +Fig. 71, in which the half section represents a small tube starting from +the bearing and terminating in the interior of an oil recess or +reservoir cast integrally with the bearing-cap. This reservoir is filled +up to the level of the tube opening. A piece of cotton waste held on a +small iron wire is inserted in the tube, part of the cotton being +allowed to hang down in the reservoir. This cotton serves as a kind of +siphon and feeds the bearing by capillary attraction with a constant +quantity of oil, the supply being regulated by varying the thickness of +the cotton. When the motor is stopped, the cotton should be removed in +order that oil-feeding may not uselessly continue. Glass, sight-feed +lubricators with stop-cocks, are very often used on crank-shafts. They +are cleaner and much more easily regulated. Of all shaft-bearing +lubricators, those which are most to be recommended are of the +revolving-ring type (Fig. 72). They presuppose, however, bearings of +large size and a special arrangement of bushings which renders their +application somewhat expensive. Furthermore, the revolving-ring system +can hardly be used in connection with engines of less than 20 +horse-power. Since the system is applied almost exclusively to +dynamo-shafts, it need not here be described in detail. As its name +indicates, it consists of a metal ring having a diameter larger than +that part of the shaft from which it is suspended and by which it is +rotated. The lower part of the ring is immersed in an oil bath so that +a certain quantity of lubricant is continually transferred to the shaft. + +[Illustration: FIG. 71.--Cotton-waste lubricator.] + +The revolving ring bearing should be fitted with a drain-cock and a +glass tube in order to control the level of the oil in the bearing. + +Many manufacturers have adopted lubricating devices for valve-stems, and +especially for exhaust-valves. The system adopted consists of a small +tube curved in any convenient direction and discharging in the +stem-guide. The free end is provided with a plug. A few drops of +petroleum are introduced once or twice a day. + +[Illustration: FIG. 72.--Ring type of bearing oiler.] + +The lubrication of an engine entails certain difficulties which are +easily overcome. One of these is the splashing of oil by the +connecting-rod head. In order that this splashed oil may be collected in +the base of the engine a suitably curved sheet-metal guard is mounted +over the crank. A more serious difficulty is presented when the oil from +a crank-bearing finds its way to the hub of the fly-wheel, whence it is +driven by the centrifugal force to the rim. The oil is not only splashed +against the walls of the engine-room, but it also destroys the adhesion +of the belt if the fly-wheel be employed as a pulley. In order to +overcome this objection the oil is prevented from spreading along the +shaft by means of a circular guard (Fig. 73) mounted on that portion of +the shaft toward the interior of the bearing. + +[Illustration: FIG. 73.--Shaft with oil-guard.] + +The problem of lubrication is of particular importance if the engine is +driven for several days at a time without a stop. This happens in the +case of mill and shop engines. Lubricators of large volume or +lubricators which can be readily filled without stopping the engine +should be employed. + + + + + CHAPTER VII + + THE CONDITIONS OF PERFECT OPERATION + + +=General Care.=--Gas-engines, as well as most machines in general, +should be kept in perfect condition. Cleanliness, even in the case of +parts of secondary importance, is indispensable. Unpainted and polished +surfaces such as the shaft of the engine, the distributing cam-shafts, +the levers, the connecting-rod and the like, should be kept in a +condition equal to that when they were new. The absence of all traces of +rust or corrosion in these parts affords sufficient evidence of the care +taken of the invisible members such as the piston, the valves, ignition +devices, and the like. + +=Lubrication.=--The rubbing surfaces of a gas-engine should be regularly +and perfectly lubricated. The absence of lost motion and backlash in the +bearings, guides, and joints is of particular importance not only +because of its influence on steady and silent running, but also on the +power developed and on the consumption. As we have already seen in the +chapter on lubrication, a special quality of oil should be employed for +the lubrication of the cylinder. The feed of the lubricator supplying +this most vital part of the engine is so regulated that it meets the +actual requirements with the utmost nicety possible. In a subsequent +chapter, in which faulty operation will be discussed, it will be shown +how too much and too little oil may cause serious trouble. + +=Tightness of the Cylinder.=--The amount of power developed depends +principally on the degree of compression to which the explosive mixture +is subjected. The economical operation of the engine depends in general +upon perfect compression. It is, therefore, necessary to keep those +parts in good order upon which the tightness of the cylinder depends. +These parts are the piston, the valves, and their joints, and the +ignition devices whether they be of the hot-tube or electrical variety. +In order to prevent leakage at the piston, the rings should be protected +from all wear. It is of the utmost importance that the surfaces both of +the piston and of the cylinder, be highly polished so that binding +cannot occur. In cleansing the cylinder, emery paper or abrasive powder +should not be employed; for the slightest particle of abrasive between +the surfaces in contact will surely cause leakage. The oil and dirt, +which is turned black by friction and which may adhere to the piston +rings, should be washed away with petroleum. Similarly the other parts +of the cylinder should be cleaned to which burnt oil tends to adhere. + +=Valve-Regrinding.=--The valves should be regularly ground. Even in +special cases where they may show no trace of rapid wear they should be +removed at least every month. In order to avoid any accident, care +should be taken in adjusting the valves after the cap has been unbolted +not to introduce a candle or a lighted match either in the +valve-chambers or in the cylinder, without first closing the gas-cock. +Furthermore, a few turns should be given to the engine, in order to +drive out any explosive mixture that may still remain in the cylinder or +the connected passages. The exhaust-valve, by reason of the high +temperature to which the disk and the seat are subjected, should receive +special attention. The valve should be ground on its seat every two or +three months at least, depending upon the load of the engine. + +=Bearings and Crosshead.=--The bushings of the engine shaft should +always be held tightly in place. The looseness to which they are liable, +particularly in gas-engines on account of the sharp explosions, tends to +unscrew the nuts and to hasten the wear of the brass, which is the +result of frequent tightening. The slightest play in the bearings of the +engine-shaft as well as in the bearings of connecting-rods increases the +sound that engines naturally produce. + +=Governor.=--The governor should receive careful attention so far as its +cleanliness is concerned; for if its operation is not easy it is apt to +become "lazy" and to lose its sensitiveness. If the governor be of the +ball type, or of the conical pendulum type operated by centrifugal +force, it is well to lubricate each joint without excess of oil. In +order to prevent the accumulation and the solidification of oil, the +governor should be lubricated from time to time with petroleum. If the +governor is actuated by inertia, which is the case in most engines of +the hit-and-miss variety, it needs less care; still, it is advisable to +keep the contact at which the thrust takes place well oiled. + +The operation of any of these governors is usually controlled by the +tension of a spring, or by a counterweight. In order to increase the +speed of the engine, or in other words, to increase the number of +admissions of gas in a given time, all that is usually necessary is to +tighten up the spring, or to change the position of the counterweight. +It should be possible to effect this adjustment while the engine is +running in such a manner that the speed can be easily changed. + +=Joints.=--In most well-built engines the caps of the valve-chests and +other removable parts are secured "metal on metal" without interposing +special joints. In other words, the surfaces are themselves sufficiently +cohesive to insure perfect tightness. In engines which are not of this +class, asbestos joints are very frequently employed, particularly at the +exhaust-valve cap and the suction-valve. + +In some engines, where for any reason it is necessary frequently to +detach the caps, certain precautions should be taken to protect the +joints so that they may not be exposed to deterioration whenever they +are removed. For this purpose, they are first immersed in water in order +to be softened, then dried and washed with olive or linseed oil on the +side upon which they rest in the engine. On the cap side they are dusted +with talcum or with graphite. Treated in this manner, the joint will +adhere on one side and will be easily released on the other. +Joints that are liable to come in contact with the gases in the +explosion-chamber should be free from all projections toward the +interior of the cylinder; for during compression these uncooled +projections may become incandescent and may thus cause premature +ignition. As a general rule when the cap is placed in position the joint +should be retightened after a certain time, when the surfaces have +become sufficiently heated. In order to tighten the joints the bolts and +nuts should not be oiled; otherwise the removal of the cap becomes +difficult. + +=Water Circulation.=--In a previous chapter, the importance of the water +circulation and the necessity of keeping the cylinder-jacket hot, have +been sufficiently dwelt upon. As the cylinder tends to become hotter +with an increase in the load, because of the greater frequency of +explosions, it is advisable to regulate the flow of the water in order +to prevent its becoming more than sufficient in quantity when the engine +is lightly loaded; for under these conditions the cylinder will be cold +and the explosive mixture will be badly utilized. A suitable temperature +of 140 to 158 degrees F. is easily maintained by adjusting the +circulation of the water. This can be accomplished by providing the +water-inlet pipe leading to the cylinder with a cock which can be opened +more or less, as may be necessary. The temperature of 140 to 158 degrees +F., which has been mentioned, may, at first blush, seem rather high +because it would be impossible to keep the hand on the outlet-pipe. The +cylinder, however, will not become overheated so long as it is possible +to hold the hand beneath the jacket near the water-inlet. This relates +only to engines having a compression of 50 to 100 lbs. per square inch. +For engines of higher compression, a lower running temperature will be +safer. On this matter the instructions of the engine maker should be +carried out. + +=Adjustment.=--Gas-engines, at least those which are built by +trustworthy firms, are always put to the brake test before they are sent +from the shops, and are adjusted to meet the requirements of maximum +efficiency. But since the nature and quality of gas necessarily vary +with each city, it is evident that an engine adjusted to develop a +certain horse-power with a gas of a certain richness, may not fulfil all +expectations if it is fed with a gas less rich, less pure, hotter, and +the like. The altitude also has some influence on the efficiency of the +engine. As it increases, the density of the mixture diminishes; that is +to say, for the same volume the engine is using a smaller amount. From +this it follows that a gas-engine ought to be adjusted as a general rule +on the spot where it is to be used. + +The fulfilment of this condition is particularly important in the case +of explosion-engines, because an advancement or retardation of only +one-half a second in igniting the explosive mixture will cause a +considerable loss in useful work. From this it would follow that +gas-engines should be periodically inspected in order that they may +operate with the highest efficiency and economy. As in the case of +steam-engines, it is advisable to take indicator records which afford +conclusive evidence of the perturbations to which every engine is +subject after having run for some time. + +Most gas-engine users either have no indicating instruments at their +disposal or else are not sufficiently versed in their employment and the +interpretation of their records to study perturbations by their means. +For this reason the advice of experts should be sought,--men who +understand the meaning of the diagrams taken and who are able by their +means to effect a considerable saving in gas. + + + + + CHAPTER VIII + + HOW TO START AN ENGINE--PRELIMINARY PRECAUTIONS + + +The first step which is taken in starting an engine driven by street-gas +is, naturally, the opening of the meter-cock and the valves between the +meter and the engine. When the gas has reached the engine, the rubber +bags will swell up and the anti-pulsator diaphragm will be forced out. +The drain-cock of the gas-pipe is then opened. In order to ascertain +whether the flow of gas is pure, a match is applied to the outlet of the +cock. The flame is allowed to burn until it changes from its original +blue color to a brilliant yellow. + +If the hot-tube system of ignition be employed, the Bunsen burner is +ignited, care being taken that the flame emerging from the tube is blue +in color. If necessary the admission of air to the burner is regulated +by the usual adjusting-sleeve. A white or smoky flame indicates an +insufficient supply of air to the burner. A characteristic sooty odor is +still other evidence of the same fact. Sometimes a white flame may be +produced by the ignition of the gas at the opening of the +adjusting-sleeve. A blue or greenish flame is that which has the highest +temperature and is the one which should, therefore, be obtained. About +five or ten minutes are required to heat up the tube, owing to the +material of which it is made. When the proper temperature has been +attained the tube becomes a dazzling cherry red in color. While the tube +is being heated up, it is well to determine whether the engine is +properly lubricated and all the cups and oil reservoirs are duly filled +up. The cotton waste of the lubricators should be properly immersed, and +the drip lubricators examined to determine whether they are supplying +their normal quantity of oil. + +The regulating-levers of the valves should be operated in order to +ascertain whether the valves drop upon their seats as they should. The +stem of the exhaust-valve should be lubricated with a few drops of +petroleum. + +If the ignition system employed be of the electric type, with batteries +and coils, tests should be made to determine whether the current passes +at the proper time on completing the circuit with the contact mounted on +the intermediary shaft. This contact should produce the characteristic +hum caused by the operation of the coil. + +If a magneto be used in connection with the ignition apparatus, its +inspection need not be undertaken whenever the engine is started, +because it is not so likely to be deranged. Still, it is advisable, as +in the case of ignition by induction-coils, to set in position the +device which retards the production of the spark. This precaution is +necessary in order to avoid a premature explosion, liable to cause a +sharp backward revolution of the fly-wheel. + +After the ignition apparatus and the lubricators have been thus +inspected, the engine is adjusted with the piston at the starting +position, which is generally indicated by a mark on the cam-shaft. The +starting position corresponds with the explosion cycle and is generally +at an angle of 40 to 60 degrees formed by the crank above the horizontal +and toward the rear of the engine. The gas-cock is opened to the proper +mark, usually shown on a small dial. If there be no mark, the cock is +slowly opened in order that no premature explosion may be caused by an +excess of gas. + +The steps outlined in the foregoing are those which must be taken with +all motors. Each system, however, necessitates peculiar precautions, +which are usually given in detailed directions furnished by the builder. + +As a general rule the engines are provided on their intermediary shafts +with a "relief" or "half-compression" cam. By means of this cam the +fly-wheel can be turned several times without the necessity of +overcoming the resistance due to complete compression. Care should be +taken, however, not to release the cam until the engine has reached a +speed sufficient to overcome this resistance. + +Engines of considerable size are commonly provided with an automatic +starting appliance. In order to manipulate the parts of which this +appliance is composed, the directions furnished by the manufacturer +must be followed. Particularly is this true of automatic starters +comprising a hand-pump by means of which an explosive mixture is +compressed,--true because in the interests of safety great care must be +taken. + +The tightness and free operation of the valves or clacks which are +intended to prevent back firing toward the pump should be made the +subject of careful investigation. Otherwise, the piston of the pump is +likely to receive a sudden shock when back firing occurs. + +When the engine has been idle for several days, it is advisable, before +starting, to give it several turns (without gas) in order to be sure +that all its parts operate normally. The same precaution should be taken +in starting an engine, if a first attempt has failed, in order to +evacuate imperfect mixtures that may be left in the cylinder. Before +this test is made, the gas-cock should, of course, be closed in order to +prevent an untimely explosion. It is advisable in starting an engine not +to bend the body over the ignition-tube, because the tube is likely to +break and to scatter dangerous fragments. + +Under no condition whatever should the fly-wheel be turned by placing +the foot upon the spokes. All that should be done is to set it in motion +by applying the hand to the rim. + +=Care During Operation.=--When the engine has acquired its normal speed, +the governor should be looked after in order that its free operation may +be assured and that all possibility of racing may be prevented. After +the engine has been running normally for a time, the cocks of the water +circulation system should be manipulated in order to adjust the supply +of water to the work performed by the engine. In other words the +cylinder should be kept hot, but not burning, as previously explained in +the paragraph in which the water-jacket is discussed. The maintenance of +a suitable temperature is extremely important so far as economy is +concerned. All the bearings should be inspected in order that hot boxes +may be obviated. + +=Stopping the Engine.=--The steps to be taken in stopping the engine are +the following: + +1. Stopping the various machines driven by the engine,--a practice which +is followed in the case of all motors; + +2. Throwing out the driving-pulley of the engine itself, if there be +one; + +3. Closing the cock between the meter and the gas-bags in order to +prevent the escape of gas and the useless stretching of the rubber of +the bags or of the anti-pulsating devices; + +4. Actuating the half-compression or relief cam as the motor slows down, +in order to prevent the recoil due to the compression; + +5. Closing the gas-admission cock; + +6. Shutting off the supply of oil of free flowing lubricators, and +lifting out the cotton from the others. + +If the engine be used to drive a dynamo, particularly a dynamo provided +with metal brushes, the precaution should be taken of lifting the +brushes before the engine is stopped in order to prevent their injury +by a return movement of the armature-shaft; + +7. Shutting off the cooling-water cock if running water is used. + +If the engine is exposed to great cold, the freezing of the water in the +jacket is prevented while the engine is at rest, either by draining the +jacket entirely, or by arranging a gas jet or a burner beneath the +cylinder for the purpose of causing the water to circulate. If such a +burner be used the cocks of the water supply pipe should, of course, be +left open. + + + + + CHAPTER IX + + PERTURBATIONS IN THE OPERATION OF ENGINES AND THEIR REMEDY + + +In this chapter will be discussed certain perturbations which affect the +operations of gas-engines to a more marked degree than lack of care in +their construction. In previous chapters defects in operation due to +various causes have been dwelt upon, such as objectionable methods in +the construction of an engine, ill-advised combination of parts, defects +of installation, and the like; and an attempt has been made to determine +in each case the conditions which must be fulfilled by the engine in +order to secure efficiency and economy at a normal load. + +=Difficulties in Starting.=--The preliminary precautions to be taken in +starting an engine having been indicated, it is to be assumed that the +advice given has been followed. Nevertheless various causes may prevent +the starting of the engine. + +=Faulty Compression.=--Defective compression, as a general rule, +prevents the ignition of the explosive mixture. Whether or not the +compression be imperfect can be ascertained by moving the piston back to +the period corresponding with compression, in other words, that position +in which all valves are closed. If no resistance be encountered, it is +evident that the air or the gaseous mixture is escaping from the +cylinder by way of the admission-valve, the exhaust-valve, or the +piston. The valves, ordinarily seated by springs, may remain open +because their stems have become bound, or because some obstruction has +dropped in between the disk and the seat. In a worn-out or badly kept +engine the valves are likely to leak. If that be the case grinding is +the only remedy. If a valve be clogged, which becomes sufficiently +evident by manipulating the controlling levers, it is necessary simply +to clean the stem and its guides in order to remove the caked oil which +accumulates in time. If the engine be new, the binding of the +valve-stems is often caused by insufficient play between the stems and +their guides. Should this prove to be the case, the defect is remedied +by rubbing the frictional surface of the stem with fine emery paper and +by lubricating it with cylinder-oil. The exhaust-valve, however, should +be lubricated only with petroleum. + +It is not unlikely that the exhaust-valve may leak for two other +reasons. In the first place, the tension of the spring which serves to +return the valve may have lessened and may be insufficient to prevent +the valve from being unseated during suction. Again, the screw or roller +serving as a contact between the lever and the valve-stem, may not have +sufficient play, so that the lengthening of the stem on account of its +expansion may prevent the valve from falling back on its seat. The +first-mentioned defect is remedied by renewing the spring, or by the +provision of an additional spring or of a counterweight in order to +prevent the stoppage of the motor. The second defect can be remedied by +regulating the contact. + +Leakage past the piston may be caused by the breaking of one or more +rings, by wear or binding of the rings, or by wear or binding of the +cylinder. The whistling caused by the air or the mixture as it passes +back proves the existence of this fault. + +=Presence of Water in the Cylinder.=--It may sometimes happen that water +may find its way into the cylinder with the gas by reason of the bad +arrangement of the piping. It may also happen that water may enter the +cylinder through the water-jacket joint. Again, the presence of water in +the cylinder may be due to condensation of the steam formed by the +chemical union of the hydrogen of the gas and the oxygen of the air, +which condensation is caused by the cool walls of the cylinder. The +water may sometimes accumulate in the exhaust pipe and box, when they +have been improperly drained, and may thus return to the cylinder. +Whatever may be its cause, however, the presence of water in the cylinder +impedes the starting of the engine, because the gases resulting from the +explosion are almost spontaneously chilled, thereby diminishing the +working pressure. + +If electric ignition be employed, drops of water may be deposited +between the contacts, thereby causing short circuits which prevent the +passing of the spark. + +If there be no drain-cock on the cylinder, the difficulty of starting +the engine can be overcome only by ceaseless attempts to set it in +motion. The leaky condition of a joint as well as the presence of a +particle of gravel in the cylinder-casting, through which the water can +pass from the jacket, is attested by the bubbling up of gas in the +water-tank at the opening of the supply tube. These bubbles are caused +by the passage of the gas through the jacket after the explosion. If +such bubbles be detected, the cylinder should be renewed or the defect +remedied. In order to obviate any danger, the stop-cocks of the +water-jacket, which have already been described in a previous chapter, +should be closed while the engine is idle. + +=Imperfect Ignition.=--The difficulties encountered in starting an +engine, and caused by imperfect ignition, vary in their nature with the +character of the ignition system employed, whether that system, for +example, be of the electric, or of the incandescent or hot tube type. +Frequently it happens that in starting an engine a hot tube may break. +If the tube be of porcelain the accident may usually be traced to +improper fitting or to the presence of water in the cylinder. If the +tube be of metal, its breaking is caused usually by a weakening of the +metal through long use--an accident that occurs more often in starting +the engine than in normal operation, because the explosions at starting +are more violent, owing to the tendency of the supply-pipes to admit an +excess of gas at the beginning. + +A misfire arising from a faulty tube in starting may be caused by an +obstruction or by leaks at the joints or in the body of the tube +itself, thereby allowing a certain quantity of the mixture to escape +before ignition. This defect in the tube is usually disclosed by a +characteristic whistling sound. + +A tube may leak either at the bottom or at the top. In the first case, +starting is very difficult, because the part of the mixture compressed +toward the tube will escape through the opening before it reaches the +incandescent zone. In the second case, ignition may be simply retarded +to so marked an extent that a sufficient motive effect cannot be +produced. An example of this retardation, artificially produced to +facilitate the starting and to obviate premature explosions, is found in +a system of ignition-tubes provided with a small cock or variable valve +(Figs. 74 and 75). + +[Illustration: FIG. 74.] + +[Illustration: FIG. 75.--Ignition-tubes provided with needle valves to +facilitate starting.] + +The mere enumeration of defects caused by leakage is sufficient to +indicate the remedy to be adopted. It may be well to recall in this +connection the important part played by the ignition-valve. If it be +leaky, or if its free operation be impeded, starting will always be +difficult. + +=Electric Ignition by Battery or Magneto.=--If the electric ignition +apparatus, whatever may be the method by which the spark is produced, be +imperfect in operation, the first step to be taken is to ascertain +whether the spark is produced at the proper time, in other words, +slightly after the dead center in the particular position given to the +admission device at starting. If a coil and a battery be employed, it is +advisable to remove the plug and to place it with its armature upon a +well-polished metal surface to produce an electrical contact, +preventing, however, the contact of the binding post with this metallic +surface. The same method of inspection is adopted with the +make-and-break apparatus of an electric magneto. In both cases it should +be ascertained whether or not there is any short-circuiting. The +contacts should be cleaned with a little benzine if they are covered +with oil or caked grease. + +If no spark is produced at the plug or at the make-and-break device it +may be inferred that the wires are broken or that the generating +apparatus is out of order. A careful examination will indicate what +measures are to be taken to cure the defects. + +=Premature Ignition.=--It has several times been stated that the moment +of ignition of the gaseous mixture has a pronounced influence on the +operation of gas-engines and upon their economy. + +Premature ignition takes place when there is a violent shock at the +moment when the piston leaps from the rear dead center to the end of the +compression stroke. The violent effects produced are all the more +harmful because they tend to overheat the interior of the engine and +thereby to increase in intensity. + +Premature ignition may be due to several causes. If a valveless hot tube +be employed it may happen that the incandescent zone is too near the +base. If the tube be provided with a valve, it very frequently happens +that the valve leaks or that it opens too soon. In the case of electric +ignition, the circuit may be completed before the proper time, because +of faulty regulation. The suggestions made in the preceding chapters +indicate the method of remedying these defects. + +Faulty ignition may have its origin not only in the method of ignition +employed, but also in excessive heating of the internal parts of the +engine, caused by continual overloading or by inadequate circulation of +water. + +Passing to those cases of premature ignition of a special nature which +are not due to any functional defect in the engine, but which are purely +accidental in origin, such as the uncleanliness of the parts within the +cylinder or the presence of some projecting part which becomes heated to +incandescence during compression, it should first be stated that these +ignitions, usually termed spontaneous, often occur well in advance of +the end of the compression stroke. They are characterized by a more +marked shock than that caused by ordinary premature ignition and +usually result in bringing the engine to a complete stop in a very short +time. These spontaneous explosions counteract to such an extent the +impulse of the compression period, during which the piston is moving +back, that they have a tendency to reverse the direction in which the +engine is running. In such cases a careful inspection and a scrupulous +cleaning of the cylinder and of the piston should be undertaken. + +The bottom of the piston is particularly likely to retain grease which +has become caked, and which is likely to become heated to incandescence +and spontaneously to ignite the explosive mixture. + +=Untimely Detonations.=--The sound produced by the explosions of a +normally operating engine can hardly be heard in the engine-room. +Untimely detonations are produced either at the exhaust, or in the +suction apparatus, near the engine itself. These detonations are noisier +than they are dangerous; still, they afford evidence of some fault in +the operation which should be remedied. + +Detonations produced at the exhaust are caused by the burning of a +charge of the explosive mixture in the exhaust-pipe, which charge, for +some reason, has not been ignited in the cylinder, and has been driven +into the exhaust-pipe, where it catches fire on coming into contact with +the incandescent gases discharged from the cylinder after the following +explosion. + +Detonations produced in the suction apparatus of the engine, which +apparatus is either arranged in the base itself or in a separate chest, +are often noisier than the foregoing. They are caused by the accidental +backward flowing of the explosive mixture, and by its ignition outside +of the cylinder. The accident may be traced to three causes: + +1. The suction-valve of the mixture may not be tight and may leak during +the period of compression, allowing a certain quantity of the mixture to +pass into the suction-chest or into the frame. When the explosion takes +place in the cylinder that part of the mixture which has passed back is +ignited, as we have just seen, thereby producing a very loud +deflagration. The obvious remedy consists in making the suction-valve +tight by carefully grinding it. + +2. It may happen that at the end of the exhaust stroke incandescent +particles may remain in the cylinder, which particles may consist of +caked oil or may be retained by poorly cooled projections. The result is +that the mixture is prematurely ignited during the suction period. + +3. The engine is so regulated, particularly in the case of English-built +engines, as to effect what is technically called "scavenging" the +products of combustion. In order to obtain this result, the +mixture-valve is opened before the end of the exhaust stroke of the +piston and the closing of the exhaust-valve. Owing to the inertia and +the speed acquired by the products of combustion shot into the +exhaust-pipe after explosion, a lowering of the pressure is produced in +the cylinder toward the end of the stroke, causing the entrance of air +by the open admission-valve and consequently effecting the scavenging of +the burnt gases, part of which would otherwise remain in the cylinder. +It is evident that if a charge of the mixture has not been normally +exploded, either because its constituents have not been mingled in the +proper proportion, or because the ignition apparatus has missed fire, +this charge at the moment of exhausting will pass out of the cylinder +without any acquired speed, and will flow back in part at the end of the +exhaust stroke past the prematurely opened admission-valve, thereby +lodging in the air suction apparatus. Despite the suction which takes +place immediately following the re-entrance of the gas into the +cylinder, a certain quantity of the mixture is still confined in the +suction-pipe and its branches, where it will catch fire at the end of +the exhaust stroke after the opening of the mixture-valve. + +In order to avoid these detonations it is necessary simply to see to it +that the mixture is regularly ignited. This is accomplished by mixing +the gas and air in proper proportions or by correcting the ignition +time. + +=Retarded Explosions.=--Retarded explosions considerably reduce the +power which an engine should normally yield, and sensibly increase the +consumption. They are due to three chief causes: (1), faulty ignition; +(2), the poor quality of the mixture; (3), compression losses. The +existence of the defect cannot be ascertained with any certainty without +the use of an indicator or of some registering device which gives +graphic records. Nevertheless, it is possible in some degree to detect +retarded explosions, simply by observing whether there is a diminution +in the power or an excessive consumption, despite the perfect operation +and good condition of all the engine parts. + +In order to remedy the defect it should be ascertained if the +compression is good, if the supply of gas is normal, and if the +conditions under which the mixture of air and gas is produced have not +been changed. Lastly, the ignition apparatus is gradually adjusted to +accelerate its operation until a point is reached when, after explosion, +shocks are produced which indicate an excessive advance. The ignition +apparatus is then adjusted to a point slightly ahead of the +corresponding position. Recalling the descriptions already given of the +various systems of ignition, the manner of regulating the moment of +ignition in each case may be summarized as follows: + +1. For the valveless incandescent tube, provided with a burner the +position of which can be varied, ignition can be accelerated by bringing +the burner nearer to the base. Retardation is effected by moving the +burner away from the base. + +2. In the case of the incandescent tube of the fixed burner type, the +moment of ignition will depend upon the length of the tube. The +retardation will be greater as the tube is shorter, and _vice versa_. + +3. If the tube be provided with an ignition-valve, the time of ignition +having been regulated by the maker, regulation need not be undertaken +except if the valve-stem be worn or the controlling-cam be distorted. +If these defects should be noted, the imperfect parts should be repaired +or renewed. + +4. In electric igniters the controlling apparatus is generally provided +with a regulating device which may be manipulated during the operation +of the motor. If the manual adjustment of the regulating apparatus be +unproductive of satisfactory results, it is advisable to ascertain +whether the spark is being produced normally. Before the engine has come +to a stop, one of the valve-casings is raised, and through the opening +thus produced it is easily seen whether the spark is of sufficient +strength, the engine in the meanwhile being turned by hand. Care should +always be taken to purge the cylinder of the gas that it may contain, in +order to prevent dangerous explosions. If the spark should prove to be +too feeble, or if there be no spark at all, despite the fact that every +part of the mechanism is properly adjusted, it may be inferred that the +fault lies with the current and is caused by + +1. Imperfect contact with the binding-posts, with the conducting wire, +or with the contact-breaking members; + +2. A short circuit in one of the dismembered pieces; + +3. The presence of a layer of oil or of caked grease forming an +insulator, injurious to induction, between the armature and the magnets; + +4. A deposit of oil or moisture on the contact-breaking parts; + +5. The exhaustion of the magnets, which, however, occurs only after +several years of use, except when the magneto has been subjected for a +long time to a high temperature. + +The mere discovery of any of these defects sufficiently indicates the +means to be adopted in remedying them. + +=Lost Motion in Moving Parts.=--Lost motion of the moving parts is due +to structural errors. Its cause is to be found in the insufficient size +of the frictional bearing surfaces, and improper proportioning of +shafts, pins, and the like. The result is a premature wear which cannot +be remedied. Imperfect adjustment, lack of care, and bad lubrication, +may also hasten the wear of certain parts. This wear is manifested in +shocks, occurring during the operation of the engine,--shocks which are +particularly noticeable at the moment of explosion. + +Besides the inconveniences mentioned, wearing of the gears and of the +moving parts leads to derangement of the power-transmitting members. + +So far as the admission and exhaust valves are concerned, the wearing of +the cams, rollers, and lever-pivots is evidenced by a retardation in the +opening of these valves and an acceleration in their closing. + +The ignition, whatever may be the system employed, is affected by lost +motion and is retarded. The engine appreciably loses in power, and its +consumption becomes excessive. + +=Overheated Bearings.=--Apart from the imperfect adjustment of a member, +it may happen that the bushings of the main bearings of the ends of the +connecting-rod, and of the piston-pivot, may become heated because of +excessive play, or of too much tightening, or of a lack of oil, or of +the employment of oil of bad quality. The overheating may lead to the +binding of frictional surfaces and even to the fusion of bushings if +they be lined with anti-friction metal. In order to avoid the +overheating of parts, it is advisable, while the engine is running, to +touch them from time to time with the back of the hand. As soon as the +slightest overheating is felt, the temperature may be lowered often by +liberal oiling. If this be inadequate and if for special reasons it is +impossible to stop the engine, the overheated part may be cooled by +spraying it with soapy water. + +If the overheating has not been detected or reduced in time, a +characteristic odor of burnt oil will be perceived, accompanied by +smoke. The part overheated will then have attained a temperature so high +that it cannot be touched with the hand. Should this occur, it is +inadvisable to employ oil, because it would immediately burn up and +would only aggravate the conditions. Cotton waste should be carefully +applied to the overheated member, and gradual spraying with soapy water +begun. + +In special cases where the lubricating openings or channels are not +likely to be obstructed, a little flowers of sulphur may be added to the +oil, if this be very fluid. Castor oil may also be successfully +employed. + +If the binding of the rubbing surfaces should prevent the reduction of +the overheated member's temperature, the engine must necessarily be +stopped, and the parts affected detached. All causes of binding are +removed by means of a steel scraper. The surfaces of the bushings and of +the shaft which they receive are smoothed with a soft file and then +polished with fine emery paper. Before the parts are replaced, the +precaution of ascertaining whether they touch at all points should be +taken. Careful inspection and copious lubrication should, of course, be +undertaken when the engine is again started. + +=Overheating of the Cylinder.=--The overheating of the cylinder may be +due to a complete lack of water in the jacket or to an accidental +diminution in the quantity of water supplied. If this discovery is made +too late, and if the cylinder has reached a very high temperature, the +circulation of the water should not be suddenly re-established, because +of the liability of breaking the casting. It is best to stop the engine +and to restore the parts to their normal condition. + +It is well to recall at this point that if the calcareous incrustation +of the water-jacket or the branch pipes should hinder the free +circulation of water, cleaning is, of course, necessary. The jacket may +be washed several times with a twenty per cent. solution of hydrochloric +acid. After this treatment the jacket should, of course, be rinsed with +fresh water before the piping of the water-circulating apparatus is +again connected. + +=Overheating of the Piston.=--If the overheating of the piston is not +due to faulty adjustment, it may be caused by lack of oil or to the +employment of a lubricant not suitable for the purpose. In a previous +chapter the importance of using a special oil for cylinder lubrication +has been insisted upon. The overheating of the piston can also result +from that of the piston-pin. Should this be the case it is advisable to +stop the engine, to ascertain the condition and the degree of +lubrication of this member and its bearing. Overheating of the piston is +manifested by an increase of the temperature of the cylinder at the +forward end. If this overheating be not checked, binding of the piston +in the cylinder is likely to result. + +=Smoke Arising from the Cylinder.=--This is generally a sign either of +overheating, which causes the oil to evaporate, or of an abnormal +passage of gas, caused by the explosion. Abnormal passage of gas may +result from wear or from distortion of the cylinder, or from wear or +breakage of the piston-rings. The result is always the overheating of +the cylinder and a reduction in compression and power. + +If the engine is well kept and shows no sign of wear, leakage may be +caused simply by the fouling of the piston-rings, which then adhere in +their grooves and have but insufficient play. This defect is obviated by +cleaning the rings in the manner explained in Chapter VII. + +Lubrication is faulty when the quantity of lubricant supplied is either +insufficient or too abundant, or when the oils employed are of bad +quality. It has already been shown that insufficient lubrication and the +utilization of bad oils leads to the overheating of the moving parts. + +Insufficient lubrication may be caused by imperfect operation of the +lubricators, or, particularly during cold weather, by too great a +viscosity or congelation of the oil. If a lubricator be imperfect in its +operation, the condition of its regulating mechanism should be +ascertained, if it has any, and an examination made to discover any +obstruction in the oil-ducts. Such obstructions are very likely to occur +in new devices which have been packed in cotton waste or excelsior, with +the result that the particles of the packing material often find their +way into openings. + +An oil may be bad in quality because of its very nature, or because of +the presence of foreign bodies. In either case an oil of better quality +should be substituted. + +The freezing of oil by intense cold may be retarded by the addition of +ordinary petroleum to the amount of 10 to 20 per cent. + +An excess of oil in the bearings results simply in an unnecessary waste +of lubricant, and the splashing of oil on the engine and about the room. +If too much oil be used in the cylinder, grave consequences may be the +result; for a certain quantity of the oil is likely to accumulate within +the cylinder, where it burns and forms a caky mass that may be heated to +incandescence and prematurely ignite the explosive mixture. Especially +in producer-gas engines is an excess of cylinder-lubricant likely to +cause such accidents. Indeed, the temperature of explosion not being as +high as in street-gas engines, the excess oil cannot be so readily +removed with certainty by evaporation or combustion. On the other hand, +the compression of the mixture being generally higher, premature +ignition is very likely to occur. + +=Back Pressure to the Exhaust.=--How the pipes and chests for the +exhaust should be arranged in order not to exert a harmful influence on +the motor has already been explained. Even if the directions given have +been followed, however, the exhaust may not operate properly from +accidental causes. Among these causes may be mentioned obstructions in +the form of foreign bodies, such as particles of rust, which drop from +the interior of the pipes after the engine has been running for some +time and which, accumulating at any place in the pipe, are likely to +clog the passage. Furthermore, the products of combustion may contain +atomized cylinder oil which finds its way into the exhaust-pipe. This +oil condenses on the walls of the elbows and bends of the pipe in a +deposit which, as it carbonizes, is converted into a hard cake and which +reduces the cross-section of the passage, thereby constituting a true +obstacle to the free exhaust of the gases. + +These various defects are manifested in a loss in engine power as well +as in an abnormal elevation of the temperature of the parts surrounding +the exhaust opening. + +=Sudden Stops.=--Sudden stops are occasioned by faulty operation of the +engine, and by imperfect fuel supply. Among the first class the chief +causes to be mentioned are the following: + +1. Overheating, which has already been discussed and which may block a +moving part. + +2. Defective ignition. + +3. Binding of the admission-valve or of the exhaust-valve, preventing +respectively suction or compression. + +4. The breaking or derangement of a member of the distributing +mechanism. + +5. A weakening of the exhaust-valve spring, so that the valve is opened +by the suction of fresh quantities of mixture. + +These faults are due to carelessness and improper inspection of the +engine. + +So far as the fuel supply of the engine is concerned, the causes of +stoppage will vary if street-gas or producer-gas be employed. In the +former case the difficulty may be occasioned by the improper operation +of the meter, by the formation of a water-pocket in the piping, by the +binding of an anti-pulsator valve, by the derangement of a +pressure-regulator, or by a sudden change in the gas pressure when no +pressure-regulator is employed. If producer-gas be used, stoppages may +be occasioned by a sudden change in the quality, quantity, or +temperature of the gas. These defects will be examined in detail in the +chapter on Gas-Producers. + + + + + CHAPTER X + + PRODUCER-GAS ENGINES + + +Thus far only street-gas or illuminating-gas engines have been +discussed. If the engine employed be small--10 to 15 horse-power, for +instance--street-gas is a fuel, the richness, purity and facility of +employment of which offsets its comparatively high cost. But the +constantly increasing necessity of generating power cheaply has led to +the employment of special gases which are easily and cheaply generated. +Such are the following: + + Blast-furnace gases, + Coke-oven gases, + Fuel-gas proper, + Mond gas, + Mixed gas, + Water-gas, + Wood-gas. + +The practical advantages resulting from the utilization of these gases +in generating power were hardly known until within the last few years. +The many uses to which these gases have been applied in Europe since +1900 have definitely proved the industrial value of producer-gas engines +in general. + +The steps which have led to this gradually increasing use of +producer-gas have been learnedly discussed and commented upon in the +instructive works and publications of Aime Witz, Professor in the +Faculty of Sciences of Lille, in those of Dugald Clerk, of London, F. +Grover, of Leeds, and Otto Gueldner, of Munich, and in those of the +American authors, Goldingham, Hiscox, Hutton, Parsell and Weed, etc. The +new tendencies in the construction of large engines may be regarded as +an interesting verification of the forecasts of these men--forecasts +which coincide with the opinion long held by the author. Aime Witz has +always been an advocate of high pressures and of increased piston speed. +English builders who made experiments in this direction conceded the +beneficial results obtained; but while they increased the original +pressure of 28 to 43 pounds per square inch employed five or six years +ago to the pressure of 85 to 100 pounds per square inch nowadays +advocated, the Germans, for the most part, have adopted, at least in +producer-gas engines, pressures of 114 to 170 pounds per square inch and +more. + +=High Compression.=--In actual practice, the problem of high pressures +is apparently very difficult of solution, and many of the best firms +still seem to cling to old ideas. The reason for their course is, +perhaps, to be found in the fact that certain experiments which they +made in raising the pressures resulted in discouraging accidents. The +explosion-chambers became overheated; valves were distorted; and +premature ignition occurred. Because the principle underlying high +pressures was improperly applied, the results obtained were poor. + +High pressures cannot be used with impunity in cylinders not especially +designed for their employment, and this is the case with most engines of +the older type, among which may be included most engines of English, +French, and particularly of American construction. In American engines +notably, the explosion-chamber, the cylinder and its jacket, are +generally cast in one piece, so that it is very difficult to allow for +the free expansion of certain members with the high and unequal +temperatures to which they are subjected (Fig. 22). + +Some builders have attempted to use high pressures without concerning +themselves in the least with a modification of the explosive mixture. +The result has been that, owing to the richness of the mixture, the +explosive pressure was increased to a point far beyond that for which +the parts were designed. Sudden starts and stops in operation, +overheating of the parts, and even breaking of crank-shafts, were the +results. The engines had gained somewhat in power, but no progress had +been made in economy of consumption, although this was the very purpose +of increasing the compression. + +High pressures render it possible to employ poor mixtures and still +insure ignition. A quality of street-gas, for example, which yields one +horse-power per hour with 17.5 cubic feet and a mixture of 1 part gas +and 8 of air compressed to 78 pounds per square inch, will give the same +power as 14 cubic feet of the same gas mixed with 12 parts of air and +compressed to 171 pounds per square inch. + +"Scavenging" of the cylinder, a practice which engineers of modern +ideas seem to consider of much importance, is better effected with high +pressures, for the simple reason that the explosion-chamber, at the end +of the return stroke, contains considerably less burnt gases when its +volume is smaller in proportion to that of the cylinder. + +In impoverishing the mixture to meet the needs of high pressures, the +explosive power is not increased and in practice hardly exceeds 365 to +427 pounds per square inch. With the higher pressures thus obtained +there is consequently no reason for subjecting the moving parts to +greater forces. + +[Illustration: FIG. 76.--Method of cooling the cylinder-head.] + +=Cooling.=--The increase in temperature of the cylinder-head and of the +valves, due wholly to high compression, is perfectly counteracted by an +arrangement which most designers seem to prefer, and which, as shown in +the accompanying diagram (Fig. 76), consists in placing the mixture and +exhaust-valves in a passage forming a kind of antechamber completely +surrounded by water. The immediate vicinity of this water assures the +perfect and equal cooling of the valve-seats. This arrangement, while it +renders it possible to reduce the size of the explosion-chamber to a +minimum, has the additional mechanical advantage of enabling the builder +to bore the seats and valve-guides with the same tool, since they are +all mounted on the same line. From the standpoint of efficiency, the +design has the advantage of permitting the introduction of the explosive +mixture without overheating it as it passes through the admission-valve, +which obtains all the benefit of the cooling of the cylinder-head, +literally surrounded as it is by water. + +In large engines the cooling effect is even heightened by separately +supplying the jackets of the cylinder-head and of the cylinder. In +engines of less power the top of the cylinder-head jacket is placed in +communication with that of the cylinder, so that the coldest water +enters at the base of the head and, after having there been heated, +passes around the cylinder in order finally to emerge at the top toward +the center. The water having been thus methodically circulated, the +useful effect and regularity of the cooling process is increased. + +Notwithstanding the care which is devoted to water circulation, it is +advisable to run the producer-gas engine "colder" than the older +street-gas types, in which the more economic speed is that at which the +water emerges from the jacket at about a temperature of 104 degrees F. +It would seem advisable to meet the requirements of piston lubrication +by reducing to a minimum the quantity of heat withdrawn by the +circulating water. Indeed, the personal experiments of the author bear +out this principle. + +For street-gas engines, however, the cylinders should be worked at the +highest possible temperature consistent with the requirements of +lubrication. It should not be forgotten that, in large engines fed with +producer-gas, economy of consumption is a secondary consideration, +because of the low quantity of fuel required. The cost, moreover, may +well be sacrificed to that steadiness of operation which is of such +great importance in large engines furnishing the power of factories; for +in such engines sudden stops seriously affect the work to be performed. +For this reason engine builders have been led to the construction of +motors provided with very effective cooling apparatus. Since the +circulation of the water around the explosion-chamber and the cylinder +is not sufficient to counteract the rise of temperature, it has become +the practice to cool separately each part likely to be subjected to +heat. The seats of the exhaust-valves, the valves themselves, the +piston, and sometimes the piston-rod, have been provided with +water-jackets. + +=Premature Ignition.=--Returning to the causes of the discouragements +encountered by some designers who endeavored to use high pressures, it +has already been mentioned that premature ignition of the explosive +mixture in cylinders not suited for high pressures is one reason for the +bad results obtained. An explanation of these results is to be found in +the high theoretical temperature corresponding with great pressures and +in the quantity of heat which must be absorbed by the walls of the +explosion-chamber. These two circumstances are in themselves sufficient +to produce spontaneous ignition of excessively rich mixtures, compressed +in an overheated chamber unprovided with a sufficient circulation of +water. A third cause of premature ignition may also be found in the old +system of ignition which, in most English engines, consists of a +metallic or porcelain tube, the interior of which communicates with the +explosion-chamber, an exterior flame being employed to heat the tube to +incandescence. In tubes of this type which are not provided with a +special ignition-valve, the time of ignition is dependent only on the +moment when the explosive mixture, driven into the tube, comes into +contact, at the end of the compression stroke, with the incandescent +zone, thereby causing the ignition. This very empirical method leads +either to an acceleration or retardation of the ignition, depending upon +the temperature of the tube, the position of the red-hot zone, its +dimensions, and the temperature of the mixture, which is determined by +the load of the engine. Although this system, the only merit of which is +its simplicity, may meet the requirements of small engines, there is not +the slightest doubt that it is quite inapplicable to those of more than +20 to 25 horse-power, for in such engines greater certainty in operation +is demanded. Even if only the more improved of the two types of hot-tube +ignition be considered, with or without valves, it must still be held +that they are inapplicable to high compression engines. The +ignition-valve is the part which suffers most from the high temperature +to which it is subjected. Its immediate proximity to the incandescent +tube, and its contact with the burning gas when it flares up, render it +almost impossible to employ any cooling arrangement. Although with the +exercise of great care it may work satisfactorily in engines of normal +pressure, it is evident that it cannot meet the requirements of high +pressure engines, because the temperature of the compressed mixture is +such that the charge is certain to catch fire by mere contact with the +overheated valve. In industrial engines of small size, premature +ignition has little, if any, effect except upon silent operation and +economic consumption. This does not hold true, however, of large +engines. Besides the inconveniences mentioned, there is also the danger +of breaking the cranks or other moving parts. The inertia of these +members is a matter of some concern, because of their weight and of the +linear speed which they attain in large engines. Some idea of this may +be obtained when it is considered that in a producer-gas or +blast-furnace-gas engine having a piston diameter of 24 inches and an +explosive pressure of 299 pounds per square inch, the force exerted at +the moment of explosion is about 132,000 pounds. Naturally, engine +builders have adopted the most certain means of avoiding premature +ignition and its grave consequences. + +The method of ignition which at present seems to be preferred to any +other for producer-gas is that employing a break-spark obtained with +the magneto apparatus previously described. Some builders of large +engines, particularly desirous of assuring steadiness of running, have +provided the explosion-chamber with two independent igniters. It may be +that they have adopted this arrangement largely for the purpose of +avoiding the inconveniences resulting from a failure of one of the +igniters, rather than for the purpose of igniting the mixture in several +places so as to obtain a more uniform ignition and one better suited for +the propagation of the flame. + +=The Governing of Engines.=--Various methods have been adopted for the +purpose of varying the motive power of an engine between no load and +full load, still preserving, however, a constant speed of rotation. +These methods consist in changing either the quantity or the quality of +the mixture admitted into the cylinder. Thus it may happen that an +engine may be supplied: + +1. With a mixture constant in quality and in quantity; + +2. With a mixture variable in quality and constant in quantity; + +3. With a mixture constant in quality and variable in quantity. + +1. _Mixture Constant in Quality and Quantity._--This method implies the +use of the hit-and-miss system of admission, in which the number of +admissions and explosions varies, while the value or the composition of +each admitted charge remains as constant as the compression itself (Fig. +34). This system has already been referred to and its simplicity fully +set forth. By its use a comparatively low consumption is obtained, even +when the engine is not running at full load. On the other hand, it has +the disadvantage of necessitating the employment of heavy fly-wheel to +preserve cyclic regularity. + +2. _Mixture Variable in Quality and Constant in Quantity._--The +governing system most commonly employed to obtain a mixture variable in +quality and constant quantity is based upon the control of the +gas-admission valve by means of a cam having a conical longitudinal +section, as shown in Fig. 35. This cam, commonly called a "conical cam," +is connected with a lever actuated from the governor. As the lever +swings under the action of the governor, the cam is shifted along the +half-speed shaft of the engine. The result is that the gas-admission +valve is opened for a longer or shorter period. + +In another system a cylindrical valve is mounted between the chamber in +which the mixture is formed and the gas-supply pipe, the valve being +carried on the same stem as the mixture-valve itself. The cylindrical +valve is displaced by the governor so as to vary the quantity of gas +drawn in with relation to the quantity of air. + +When the engines are fed with producer-gas the parts which have just +been described should be frequently inspected and cleaned; for they are +only too easily fouled. + +Engines thus governed should be run at high pressure so as to insure +the ignition of the producer-gas mixtures formed when the position of +the cam corresponds with the minimum opening of the gas-valve. Powerful +governors should be employed, capable of overcoming the resistance +offered by the cylindrical valve or the cam. + +It may often happen that variations in the load of the engine render it +necessary to actuate the air valve, so as to obtain a mixture which will +be ignited and exploded under the best possible conditions. + +3. _Mixture Constant in Quality and Variable in Quantity._--In supplying +an engine with a mixture constant in quality and variable in quantity, +the compression does not remain constant. The quantity of mixture drawn +in by the cylinder may even be so far reduced that the pressure drops +below the point at which ignition takes place. For that reason engines +of this type should be run at high pressures. + +The variation of the quantity of mixture may be effected in various +ways. The simplest arrangement consists in mounting a butterfly-valve in +the mixture pipe, which valve is controlled by the governor and +throttles the passage to a greater or lesser degree. A very striking +solution of the problem consists in varying the opening of the +mixture-valve itself. To attain this end the valve is moved by levers. +The point of application of one of these levers is displaced under the +action of the governor so as to vary the travel of the valve within +predetermined limits. Under these conditions a mixture of constant +homogeneity is introduced into the cylinder, so proportioned as to +insure ignition even at low pressures. + +[Illustration: FIG. 76_a_.--Governing system for producer-gas engines.] + +In recent experiments conducted by the author it was proved that with +this governing system ignition still takes place even though the +pressure has dropped to 43 pounds per square inch. This system has the +merit of rendering it possible to employ ordinary governors of moderate +size, since the resistance to be overcome at the point of application of +the lever is comparatively small. In the accompanying illustration the +Otto Deutz system is illustrated. + + + + + CHAPTER XI + + PRODUCER-GAS + + +It may here be not amiss to point out the differences between +illuminating gas and those gases which are called in English "producer" +gases, and in French "poor" gases, because of their low calorific value. + +=Street-Gas.=--This gas, the composition of which varies with different +localities, has a calorific value, which is a function of its +composition, and which varies from 5,000 to 5,600 calories per cubic +meter (19,841 to 24,896 B.T.U. per 35.31 cubic feet) measured at +constant pressure and corrected to 0 degrees C. (32 degrees F.) at a +pressure of 760 millimeters (29.9 inches of mercury, or atmospheric +pressure), not including the latent heat of the water of condensation. +The following table gives the average volumetric composition of +illuminating gas in various cities: + + ____________________________________________________________________ + | + | Cities. + |______________________________________________ + | | | | | + | | Manches- | New | | + | London. | ter. | York. | Paris. | Berlin. + _____________________|_________|__________|_______|________|________ + | | | | | + Hydrogen | 48 | 46 | 40 | 52 | 50 + Carbon monoxide | 4 | 7 | 4 | 6 | 9 + Methane | 38 | 35 | 37 | 32 | 33 + Various hydrocarbons | 4 | 6 | 7 | 6 | 5 + Carbon dioxide | | 4 | 3 | | 2 + Nitrogen | 5 | 2 | 8 | 4 | 1 + Oxygen | 1 | ... | 1 | ... | ... + |_________|__________|_______|________|________ + | | | | | + | 100 | 100 | 100 | 100 | 100 + _____________________|_________|__________|_______|________|________ + +Furthermore, these constituents vary within certain limits. This is also +true of the calorific value. Experiments made by the author have +demonstrated that in the same place at an interval of a few hours, +variations of approximately ten per cent. occur. + +=Composition of Producer-Gases.=--The average chemical composition of +producer-gases varies with the conditions under which they are generated +and the nature of the fuel. The following are the proportions of its +constituents expressed volumetrically: + + Table Headings-- + A: Blast Furnace. + B: Producer. + C: Mond. + D: Mixed (Fichet). + E: Water (Stache). + F: Wood (Riche). + ________________________________________________________________________ + | + | Gas. + |_________________________________________________ + | | | | | | + | A. | B. | C. | D. | E. | F. + ______________________|_______|_______|_______|________|________|_______ + | | | | | | + Nitrogen and oxygen | 60 | 59 | 42 | 50 | 5 | 1 + Carbon monoxide | 24 | 25 | 11 | 20 | 40 | 29 + Carbon dioxide | 12 | 5 | 16 | 7 | 4 | 11 + Hydrocarbons | 2 | 2 | 2 | 3 | 1 | 15 + Hydrogen | 2 | 9 | 29 | 20 | 50 | 44 + |_______|_______|_______|________|________|_______ + | | | | | | + | 100 | 100 | 100 | 100 | 100 | 100 + |_______|_______|_______|________|________|_______ + Calorific value | | | | | | + in calories. | 950 | 1,100 | 1,400 | 1,300 | 2,400 | 2,960 + Average weight of a | | | | | | + cubic meter in kilos| 1.30 | 1.1 | 1.02 | 1.05 | 0.680 | 0.824 + Or of a cubic foot | | | | | | + in pounds | 0.008 | 0.007 | 0.006 | 0.0068 | 0.0042 | 0.0051 + ______________________|_______|_______|_______|________|________|_______ + +Blast-furnace gas has been used for generating power by means of +gas-engines for about ten years. At the present time it is used in +engines of very high power, a discussion of which engines more properly +belongs to a work on metallurgy, and has no place, therefore, in a +manual such as this. + +Producer-gas, in the true sense of the term, is generated in special +apparatus either under pressure or by suction in a manner to be +described in the following chapters. + +Mond gas is produced in generators of the blowing or pressure type from +bituminous coal, necessitating the employment of special purifiers and +permitting the collection of the by-products of the fractional +distillation of the coal. Mond gas plants are, therefore, rather +complicated and can be advantageously utilized only for large engines. +More exhaustive information can be obtained from the descriptions +published by the builders of Mond gas generators. + +Mixed gas is generated in apparatus arranged so that the retort is kept +at a high temperature, thereby producing a gas richer in hydrogen than +that made by producers. It should be observed that in practice the +generators at present used yield a producer-gas, the calorific value of +which fluctuates between 1,000 and 1,400 calories per cubic meter (3,968 +to 5,158 B.T.U. per 35.31 cubic feet); and the composition varies +accordingly, in the manner that has already been indicated in the tables +for producer-gas and mixed gas. There is no necessity, therefore, for +drawing a distinction between these two qualities of gas. + +Water-gas should theoretically be composed of 50 per cent. carbon +monoxide and 50 per cent. hydrogen, resulting from the decomposition of +steam by incandescent coal. In practice, however, it contains a little +nitrogen and carbon dioxide. The gas is obtained from generators in +which air is alternately blown in to fan the fire and then steam to +produce gas. Water-gas is employed in soldering on account of its +reducing properties and of the high temperature of its flame. The great +quantity of carbon monoxide which it contains renders it very poisonous +and exceedingly dangerous, because it is generated under pressure. From +the economical standpoint, its generation is more expensive than that of +producer-gas, for which reason its employment in gas-engines is hardly +of much value. + +Wood-gas, the composition of which has already been given, is generated +in apparatus of the Riche type, the principle of which consists in +heating a cast retort charged with any kind of fuel, namely wood, and +vertically mounted on a masonry base. + +This apparatus should be of particular interest to the proprietors of +sawmills, furniture factories, and the like, since it offers a means of +using the waste products of their plants. + +The relatively high proportion of carbon monoxide in producer-gas is +objectionable from a hygienic standpoint, so much so, indeed, that it +has attracted the attention of manufacturers. Carbon monoxide, the +specific gravity of which is 0.967, is a gas peculiarly poisonous and +dangerous. It cannot be breathed without baneful effects, and is even +more dangerous than carbonic-acid gas, which eventually causes +asphyxiation by reducing the quantity of oxygen in the air. For this +reason, it is necessary to take the utmost precaution in efficiently and +continuously ventilating the rooms in which the gas-generators and their +accessories are installed. This suggestion should be followed, above +all, when the apparatus in question are installed in cellars and +basements. As a further precaution, where the plant is rather large a +workman should not be allowed to enter the generator room alone. + +Blowing-generators, or those in which the gas is produced under +pressure, are more dangerous than suction-generators. In the former a +leaky joint may cause the vitiation of the surrounding air as the +producer-gas escapes; in the suction apparatus the same fault simply +causes more air to be drawn in. + +Dr. Melotte recommends the following procedure in cases of carbon +monoxide asphyxiation: + + + CARBON MONOXIDE ASPHYXIATION + +Cases of poisoning by carbon monoxide are both frequent and dangerous. +The gas is extremely poisonous, and all the more dangerous because it is +odorless, colorless and tasteless. When it comes into contact with the +blood, it forms a combination so stable that it is reacted upon by the +oxygen of the air only with difficulty. It follows, therefore, that with +each respiration of air charged with carbon monoxide, a certain quantity +of blood is poisoned. In consequence of this, there is a possibility of +poisoning in open air. + +=Symptoms.=--The symptoms observed will vary with the manner in which +the blood has been poisoned. There are two ways in which this poisoning +can occur. The one depends upon whether the atmosphere contains an +excess of carbon monoxide; the other whether the air breathed contains +only traces of the gas. + +=Gradual, Rapid Asphyxiation.=--At first a vague sickness is felt, +rapidly followed by violent headaches, vertigo, anxiety, oppression, +dimness of vision, beating of the pulse at the temples, hallucinations, +and an irresistible desire to sleep. If at this stage the patient has a +sufficient idea of danger to prompt him to open a window or door, he +will escape death. + +In the second stage, the victim's legs are paralyzed, but he can still +move his arms and his head. The mind still preserves its clearness, and +in a measure assists the further process of asphyxiation because of its +impotency. Then follow coma and death. + +=Slow, Chronic Asphyxiation.=--Slow, chronic asphyxiation is not +infrequent. Its symptoms are often difficult to detect. Poisoning is +manifested by weakness, cephalalgia, vomiting, pallor, general anemia, +lassitude, and local paralysis. If any of these symptoms appear in the +men who work in the vicinity of the producers, immediate steps should be +taken to prevent the possibility of carbon monoxide asphyxiation. + + + FIRST AID IN CASES OF CARBON MONOXIDE POISONING + +It has already been stated that the oxygen of the air has no oxidizing +effect upon blood contaminated by carbon monoxide. Only a liberal +current of pure oxygen can oxidize the combination formed and render +hematosis possible. This liberal current can be obtained from an oxygen +tank of the portable variety, provided with a tube carrying at its free +end a mask which is held over the mouth and the nostrils. The +absorption of gas takes place by artificial respiration, which is +effected in several ways. The most practical of these are the Sylvester +and Pacini methods. + +=Sylvester Method.=--The patient is laid on his back. His arms are +raised over his head and then brought back on each side of the body. +This operation is repeated fifteen times per minute approximately. The +method is very frequently employed and is excellent in its results. + +=The Pacini Method.=--Four fingers are placed in the pit of the arm, +with the thumb on the shoulder. The shoulder is then alternately raised +and lowered, producing a marked expansion of the chest. This method is +the more effective of the two. The movements described are repeated +fifteen to twenty times each minute very rhythmically. + +One or the other of these two methods of treatment should be immediately +applied in serious cases. Certain preliminary precautions should be +taken in all cases, however. The patient should be carried to a +well-ventilated and moderately heated room, stripped of his clothes, and +warmed by water-bottles and heated linen. Reflex action should be +excited, the peripheral nervous system stimulated in order to contract +the heart and the respiratory muscles, and the precordial region +cauterized. In addition to this treatment, the region of the diaphragm +should be rubbed and pinched, the skin rubbed, cold showers given, +flagellations administered, urtications (whipping with nettles) +undertaken, the skin and the mucous membranes excited, the mucous +membrane of the nose and of the pharynx titillated with a feather dipped +in ammonia, alcohol, vinegar, or lemon juice. Rhythmic traction of the +tongue is effective when carried out as follows: The tongue is seized +with a forceps and kept extended by means of a coarse thread. It is then +pulled out from the mouth sharply and allowed to reenter after each +traction. These movements should be rhythmic and should be repeated +fifteen to twenty times a minute. + +All these efforts should be continued for several hours. When the +patient has finally been revived, he should be placed in a warm bed. +Stimulants such as wine, coffee, and the like should be administered. If +the head should be congested, local blood-letting should be resorted to +and four or six leeches applied behind the ears. It should be borne in +mind that the various steps enumerated are to be taken pending the +arrival of a physician. + + + IMPURITIES OF THE GASES + +Most of the coal used in generating producer-gas contains sulphur. +Sulphuretted hydrogen is thus produced, which mixes with the gas and +imparts to it its characteristic odor. In some gas-generators, purifiers +are employed in which sawdust mixed with iron salts is utilized, with +the result that a combination is formed with the sulphuretted hydrogen, +thereby removing it from the producer-gas. In other forms of generators +a more summary method of purification is adopted, so that traces of +sulphuretted hydrogen still remain. Since this gas attacks copper, the +employment of this metal is not advisable for the following apparatus: +Generator (openings, cock for testing the gas); piping (gas-pressure +cocks, drain and pet cocks); engine (gas-admission cock, lubricating +joint in the cylinder, valves and cocks of the compressed-air +starting-pipe). + +The distillation of coal in generators results in the formation of +ammonia gas. This also has a corrosive action on copper and its alloys; +but owing to its great solubility, it is eliminated by the waters of the +"scrubber" and does not reach the engine. + + + PRODUCTION AND CONSUMPTION + +The quantity of gas produced in most generators varies from 6.4 to 8.2 +pounds per cubic foot of raw coal burnt in the generator. The engine +consumes per horse-power per hour 70 to 115 cubic feet of gas, depending +upon its richness. + + + + + CHAPTER XII + + PRESSURE GAS-PRODUCERS + + +As we have already seen, producer-gas as a fuel for engines may be +generated in two kinds of apparatus, the one operating under pressure, +and the other by suction. + +=Dowson Gas-Producers.=--The first pressure-generators were introduced +by Dowson of London and necessitated installations of quite a +complicated nature. Later improvements made by the designers contributed +much to the general employment of their system. Many installations +varying from 50 to 100 horsepower and more may be found in the United +Kingdom, all of them made by Dowson. Indeed, for a long time the name of +Dowson was coupled with producer-gas itself. The Dowson system +necessitates the utilization of anthracite or of comparatively hard +coal, such as that mined in Wales and Pennsylvania. Owing to the +necessity of employing this special quality of coal the Dowson system +and the systems that sprang from it were burdened with cooling, washing, +and purifying apparatus, which complicated the installations to such an +extent that they resembled gas works. The generator that took the place +of the retort was fed with air and steam, blown in under pressure, +necessitating the employment of a boiler. Furthermore, the production +of the gas under pressure necessitated the use of a gasometer for its +collection before it was supplied to the engine-cylinder. Such +Installations were evidently costly, and were, moreover, difficult to +maintain in proper working order. Nevertheless, there are many cases in +which they must be industrially employed. + +[Illustration: FIG. 77.--A complete Dowson producer-gas plant.] + +[Illustration: FIG. 78.--A Simplex producer-gas plant.] + +Among these may be cited works in which producer-gas is employed as a +furnace fuel or as a soldering or roasting medium. Still other cases are +those in which the producer-gas must be piped to some distance from a +central generating installation to various engines, in the manner +rendered familiar in gas-lighting practice. + +Most pressure gas-generators have been copied from the original type +invented by Dowson. These include a generator in which the gas is +produced; an injector fed by a boiler; a fan or a compressor by means of +which a mixture of steam and air is blown under the generator-furnace; +washing apparatus termed "scrubbers"; gas-purifying apparatus; and a +gas-holder (Fig. 77). + +=Generators.=--The generator consists of a retort made of refractory +clay, vertically mounted, and cylindrical or conical in form. This +retort is protected on its exterior by a metal jacket with an +intermediate layer of sand which serves to reduce the heat lost by +radiation. The fuel is charged through the top of the retort, which is +provided with a double closure in order to prevent the entrance of air +during the charging operation. The generator rests on a grid arranged at +the base of the retort, upon which grid the ashes fall. The outlet of +the injector-pipe opens into the ash-pit, and this injector constantly +supplies a mixture of steam and air. The mixture is generally +superheated by passing it through a coil arranged in the fire-box of the +boiler, in the generator, or in the outlet for burnt gases. Sometimes +the air is subjected to a preliminary heating by recuperating in some +way the waste heat of the apparatus. + +The chief features in the arrangement of generators which have received +the attention of manufacturers are the following: Good distribution of +the fuel in charging; easy descent of the fuel; reduction of the +destructive action of the clinkers on the walls; means for cleaning the +grate without interfering with the generation of gas; prevention of +leakage. Many devices have been employed to fulfil these requisites. + +A perfect distribution of the fuel during charging is attained chiefly +by the form of the hopper, and of its gate, which is generally conical. +In most apparatus the gate opens toward the interior of the generator, +and the inclination of its walls causes a uniform scattering of the fuel +in the retort. It is all the more necessary to disperse the fuel in this +manner when the cross-section of the retort is small compared with its +height. + +_The facility of the fuel's_ descent is dependent largely upon the +nature and the size of the coal employed. Porous coal gives better +results than dense and compact coal. It is therefore preferable to +employ screened coal free from dust in pieces each the size of a +hazel-nut. The various sections given to the interior, including as they +do cylindrical forms, truncated at the summit or the base, partially +truncated toward the base and the like, would lead to the conclusion +that this question is not of the importance which some writers would +have us believe. Still, it must be considered that if the fuel drops +slowly, its prolonged detention within the walls of the hopper and its +transformation into fusible slag may result in a disintegration of the +refractory lining of the furnace. + +The quantity of steam injected, greater or less, according to the nature +of the fuel, renders it possible to obtain friable slags and +consequently to prevent grave injury to the retort. Red-ash coal is in +general fusible, containing as it does some iron. Its temperature of +fusion varies between 1,832 to 2,732 degrees F. + +_Cleanliness_ is most important so far as the operation of the generator +is concerned. It should be possible to scrape the generator during +operation without changing the composition of the gas, when the +incandescent zone is chilled, or an excess of air is introduced, or the +steam-injector be momentarily thrown out of operation. Mechanical +cleaners with movable grates or revolving beds have the merit of causing +the ashes to drop without interfering with the operation of the +apparatus. The same meritorious feature is characteristic of ash-pits +having water-sealed joints. + +Pressure gas-generators need not be as perfectly gas-tight as suction +apparatus. Leakage of gas, which is usually manifested by a +characteristic odor, results in a loss of consumption and renders the +air unfit to breathe. + +A generator should be provided in its upper part with openings through +which a poker can easily be introduced in order to shake up the fuel and +to dislodge the clinkers which tend to form and which cause the +principal defects in operation, particularly with fuels that tend to +swell, cake, and adhere to the furnace walls when heated. Many +apparatus, moreover, are provided with lateral openings having mica +panes through which the progress of combustion can be observed (Fig. +79). + +[Illustration: FIG. 79.--Fichet-Heurtey producer with rotating +bed-plate.] + +=Air-Blast.=--The system by which air and steam are injected +necessitates the employment of a steam-boiler of 75 pounds pressure. +This method of blowing, which is rather complicated, has the +disadvantage of varying in feed with the pressure of the steam in the +boiler, which pressure is not easily maintained at a given number of +pounds per square inch. Moreover, when more or less resistance is +offered by the fuel in the generator the quantity of air which is +injected is likely to be diminished in quantity while the quantity of +steam remains the same. The result is a change in speed which follows +from the modification of the proportions of the two elements. For these +reasons some manufacturers have resorted of late years to the employment +of fans and blowers. + +[Illustration: FIG. 80.--Koerting blower.] + +=Blowers.=--The fans or blowers employed vary considerably in +arrangement. Most of them are based on the Koerting system (Fig. 80), +and comprise essentially (1) a tube through which the steam is supplied +under pressure, and (2) a cylindro-conical blast-pipe. The tube is +placed in the axis of the blast-pipe at its outer opening. As it escapes +under pressure the steam is caught in the blast-pipe and draws with it a +certain quantity of air, which can be regulated. It is important that +these injection blowers should operate in such a manner that the +pressure and the feed of air and steam can be controlled. + +=Fans.=--Mechanical blowers have the advantage of dispensing with the +employment of steam under pressure and the consequent installation of a +boiler (Fig. 78). Driven by the engine itself or from some separate +source of power, these apparatus are easily placed in position, require +no great amount of attention, and utilize but little energy. They are +either of the centrifugal type or of the rotary type, exemplified in the +Root blower (Fig. 81). The latter system has the advantage of high +efficiency, and of enabling comparatively high pressures--19 to 27 +inches of water--to be attained, which, however, are used only for +special fuels, such as lignite, peat, and the like. The air supplied by +the blower, before reaching the fire-box, is superheated, either before +or after it is charged with steam. + +[Illustration: FIG. 81.--Root blower.] + +=Compressors.=--In some installations air is supplied by compressor +under the high pressure of 70 to 90 pounds per square inch, and seem +well adapted to the production of a gas of good quality. Moreover, +neither tar nor ammoniacal waters are produced. The Gardie producer may +be considered typical of this class of apparatus (Fig. 82). The chief +feature of this producer is to be found in simple washing and purifying +apparatus. It may be well to state here that the compression of air at +high pressure occasions some complications, and a considerable +expenditure of power. + +[Illustration: FIG. 82.--Gardie producer.] + +=Exhausters.=--Some designers have invented devices which draw gas into +the generator whence it is supplied to the engines, these suction +apparatus being connected with the blowers or used separately. But with +the exception of a few special instances, such arrangements are not +widely used--at least not for the production of motive power alone. + +Whatever may be the arrangement employed for the introduction of a +mixture of air and steam under the grate of the generator, the +blast-pipe as a general rule discharges toward the center of the +apparatus. Still, in large producers it becomes desirable to provide a +means for varying the quantity of air and steam within wide limits so as +to regulate the heat of the fire. For that reason several outlets are +symmetrically arranged below the fuel. + +[Illustration: FIG. 83.--Sawdust purifier.] + +=Washing and Purifying.=--In pressure producers the gas is generally +washed and purified with much more care than in suction apparatus. Given +a sufficient pressure, the gas can be driven through the different +apparatus and the spaces between the material which they contain without +any difficulty. The gases emerge from the generator highly heated, and +this heat is used either to warm the injection water or to generate the +steam fed to the furnace. The gases then enter the washing apparatus, +which most frequently consists of a succession of contrivances in which +the gas is washed either by causing it to bubble up through the water, +or by subjecting it to superficial friction against a sheet of water, or +by systematically circulating it in a mass of continuously besprinkled +inert material. The object of washing is to remove the dust contained in +the gas and to precipitate it in the form of a slime which can be +removed by flushing. + +[Illustration: FIG. 84.--Moss or fiber purifier.] + +Physical purification thus begun is completed by passing the gas through +a filtering bed consisting of fiber, sawdust, or moss (Figs. 83 and 84). +Chemical purification if it is necessary, is effected by means of +calcium hydrate, iron oxide, or, still better, by a mixture of lime and +iron sulphate. This filtering material must necessarily be renewed after +it is exhausted. + +[Illustration: FIG. 85.--Combined gas-holder and washer.] + +=Gas-Holder.=--The gas-holder is composed essentially of a tank and a +bell. Sometimes, for the purpose of simplifying the apparatus, the tank +is so arranged as to take the place of a washer or scrubber (Fig. 85). +The bell should be provided with mechanism which, when the bell is full, +automatically diminishes or stops the generation of gas. It is advisable +to provide the bell with a blow or flap valve opening toward the +interior. If, therefore, it should happen that the gas supply is cut off +while the engine still continues to run, the suction of the engine will +not draw the water from the tank of the gas-holder. + +When engines are employed the horse-power of which does not exceed 50, +it is sometimes customary to use the water of the tank (placed at a +higher elevation than the engine) to cool the cylinder. In this manner +the cost of installing special reservoirs is saved. If such an +arrangement be employed, however, the quantity of water contained in the +tank should be at least double that ordinarily contained in reservoirs. +If this precaution be not observed, the water may become excessively +heated and expand the gas in the bell. + +The volume of the bell of the gas-holder should preferably be +not less than about 3 cubic feet per effective horse-power of the +engine to be supplied. Under these circumstances the bell acts as a +pressure-regulator, assures a sufficient homogeneity of the remaining +gas, and renders it possible to supply the engine during the short +intervals in which it is necessary to stop the blast to poke the fire. +But if the engine consumes 60 to 80 cubic feet of producer-gas per +horse-power per hour, the bell must be very much larger in size if the +generation of gas is to be checked for some time. + +It may be well to recall here that coal is not the only fuel which lends +itself to the generation of gas suitable for driving engines, but that +some generators are able to utilize lignite, peat, and the like. In +others, straw, wood, shavings and sawdust, tannery waste, and other +organic matter is burnt with an efficiency very much higher than that +which they would give in the fireboxes of steam-boilers. + +[Illustration: FIG. 86.--Otto Deutz lignite-producer.] + +=Lignite and Peat Producers.=--Lignite and peat generators (Fig. 86) +cannot operate on the suction principle because of the resistance +offered to the passage of gas by the layer of fuel. This resistance is +considerable and extremely variable. Consequently, lignite and peat +generators must operate on the pressure principle by utilizing a blast +of air or a steam injector, depending upon the amount of water contained +in the lignite. As a general rule a Root blower operating at a pressure +of 8 to 27 inches of water, depending upon the quality of the lignite, +is employed. These generators are not to be recommended for powers less +than 50 horse-power, for the cost of the apparatus becomes too great. + +The best lignite is that which, after combustion, leaves a fine ash and +no agglomerated clinker. Lignite has the peculiarity of forming dust +which ignites very easily when air is admitted into the generator. For +this reason the generator should not be scraped during operation, in +order to avoid the production of a flame which may escape from the +apparatus. + +The scrubber is simply a column without coke, and is provided with an +interior sprinkler. The coke is too rapidly clogged with tar. Much of +this tar is deposited in a chamber which precedes the gas-holder. +Several quarts of tar may be tapped from the chamber daily. + +The gas-holder serves merely to regulate the production of gas. The +pipes leading to the engine should be cleaned several times each month, +in order to remove the thin layer of tar which is deposited within them. + +There are many kinds of lignite, and the gas-generator should be +constructed to meet the peculiar requirements of the variety employed. +The layer of fuel should be such in thickness that the gas as it emerges +from the generator has a temperature of about 77 degrees F. This is the +temperature of the gas which leaves the scrubber in the case of +anthracite-generators. If the lignite contains much water, the greater +part is retained in the washer by the gas in the form of drops. +Sometimes the water drips through the grate of the generator. +Lignite-generators may also be operated with peat, and even with town +refuse, with slight modifications. The consumption per horse-power per +hour is 3.3 pounds of lignite containing 2,400 calories (9,424.9 +B.T.U.). In order to generate the same power with a boiler and +steam-engine, 8.8 pounds would be required. An engine driven unloaded +with fuel furnished by a lignite-generator will consume 50 per cent. of +the weight of the fuel required at full load. This depends upon the +proportion of water contained in the lignite and on losses of heat by +radiation from the generator. In street-gas engines running without +load, the absorption is 20 per cent., in anthracite-generators 40 per +cent. of the consumption at full load. + +Passing now to the utilization of wood, of which something has already +been said in Chapter XI, two entirely distinct processes are +successfully employed in apparatus of the Riche type, these processes +depending upon the form of the wood used--whether, in other words, the +wood be consumed in the form of sticks or blocks or in the form of +chips, sawdust, bark, and the like, all of them the wastes of factories +in which wood is used. + +=Distilling-Producers.=--If the wood consists of logs, it is burnt in a +generator comprising a fire-box and a distilling retort. The fire-box is +charged with ordinary coal which serves to heat the retort to redness. +The wood is discharged through the top of the retort, and the gas, +produced by the distillation, escapes through the bottom and passes to +the washing apparatus. The base of the retort is heated to about 1,652 +degrees F., while at the top this temperature is reduced to 752 degrees +F. The wood thus treated is transformed into charcoal, which is a +by-product of some value. + +[Illustration: FIG. 87.--Riche distilling-producer.] + +The lower part of this cast retort (Fig. 87) is lined with charcoal, the +residue of previous distillations. The wood which is introduced in the +upper part of the retort is distilled in the chamber. The retort is held +by its own weight in a socket on the foot, which socket is lined with a +special refractory cement, made of silicate, asbestos forming the joint. +The products of combustion, issuing from the furnace, pass by way of +the flue to the lower part of the casing, and raise the temperature of +the retort and the charcoal it contains to that of a cherry red (1,652 +degrees F.). These products of combustion then float to the upper part +of the casing and heat the top of the retort to a temperature of about +752 degrees F., in which part the wood or the wooden waste to be +distilled is enclosed. Thence the products of combustion pass through a +horizontal flue, provided with a damper, into a collecting flue by which +they are led to the smoke-stack. The products of distillation formed in +the chamber, having no outlet at the top of the retort, must traverse +the zone filled with incandescent carbon. The condensible products are +conducted as permanent gases (carbonic-acid gas in the state of carbon +monoxide) and are collected in the receptacle, after having passed the +funnel and the bell of the purifying apparatus. + +A gas-furnace is formed by grouping in a single mass of masonry a +certain number of elements of the kind just described. It is essential +that the retorts should be vertically placed, that they be made only of +cast metal and not of refractory clay, and, finally, that their diameter +be not much more than 10 inches, which size has been found most +expedient in practice. The gas collected in the bell or in one or more +of the receptacles passes into the gasometer and then into the service +pipes. If 2.2 pounds of wood be distilled by burning in the furnace 8/9 +of a pound of coal of average quality or 2.2 pounds of wood (either +sawdust or waste), 24.5 to 28 cubic feet of gas will be generated +having a thermal value of 3,000 to 3,300 calories per cubic meter +(11,904 to 13,094 B.T.U. per 35.31 cubic feet), and a residue 44 pounds +of charcoal will be left. + +In practice only the wood of commerce containing in the green state 20 +to 40 per cent. of water, depending upon the variety, is used. Hornbeam +contains the least water (18 per cent.), while elmwood and spruce +contain the most (44 to 45 per cent.). + +The blast apparatus of the generator being started, the gas is supplied +under pressure. By reason of its permanent composition and its richness, +it is an excellent substitute for street-gas in incandescent lighting, a +good furnace fuel reducing agent. + +_Producers Using Wood Waste, Sawdust, and the Like._--If waste wood in +the form of shavings, sawdust, straw, bark, and the like, should be +employed, a still higher efficiency is obtained with self-reducing +generators of the Riche type. + +_Combustion-Generators._--In combustion-generators (Fig. 88) the fuel is +burnt and not distilled. The generator comprises two distinct elements. +The first is the generator proper, in which the combustion takes place. +Upon it is placed a hopper or fuel supply box. The Second element is the +reducer, in which by an independent process the reduction of the +carbonic-acid gas, the dissociation of the steam, and the transformation +of the hydrocarbons takes place. The generator is provided at its base +with a grate having oblique bars in tiers, which grate is furnished with +a channel in which the water for the generation of hydrogen flows. On a +level with this grate, at the opposite side, is a flue communicating +with the reduction column of coke. The incandescent zone of the +generator should not extend above the level of the grate. Instead of +passing through the layers of fresh fuel and out by way of the top, the +gas generated flows directly into the reduction column where it heats +the coke to incandescence. The high temperature to which the coke is +subjected, coupled with the injection of air, effects useful reactions. +This additional air, however, is not used if the fuel is free from all +products of distillation. + +[Illustration: FIG. 88.--Riche combustion-producer.] + +Experience has shown that gas of 1,000 to 1100 calories per cubic meter +(3,968 to 4,365 B.T.U. per 35.31 cubic feet), which heat content is +necessary to develop one horse-power per hour, can be obtained with 3.96 +pounds of wood in the form of shavings and sawdust containing 30 per +cent. of water. The corresponding quantity of coke consumed in the +reduction column is insignificant, and may be placed at about 0.112 +pounds per horse-power per hour. + +It has been proven in actual practice that, both in the distilling and +combustion types of apparatus, the wood, either in the green state or in +the form of saw-mill waste, may contain as much as 60 per cent. of +water. Either of the two systems can be operated under pressure with an +air-blast, in which case a gas-holder and bell must be employed. The gas +as it passes from the generator to the gas-holder is conducted through a +cooler and washer and through a moss filter, which removes traces of the +products that may have escaped the distillation. + +=Inverted Combustion.=--With a few exceptions the pressure-generators +which have been described, as well as suction gas-producers which will +be later discussed, are fed with anthracite coal or with coke. They +cannot be operated with moderately soft or bituminous coal. For this +reason they limit the employment of producer-gas engines. Manufacturers +have long sought generators in which any fuel whatever can be consumed. + +Among the producers which seem to overcome the objections cited to a +certain degree, are those which are based on the principle of inverted +combustion. These apparatus embody the ideas of Ebelmen, the products of +distillation being decomposed by passing them over layers of +incandescent fuel. + +[Illustration: FIG. 89.--Deschamps inverted-combustion producer.] + +Many writers place in the class of inverted combustion producers, +apparatus of the Riche, Thwaite, and Duff type, in which this idea is +also carried out. Riche employs an independent incandescent mass to +reduce the products of distillation of another mass. Thwaite employs two +vessels which serve alternately as distilling retorts and reducing +columns. Duff draws in the products of distillation for the purpose of +blowing them under the fire. All these generators can hardly be said to +be of the inverted combustion type. + +[Illustration: FIG. 90.--Fange-Chavanon inverted-combustion producer.] + +The generators of Deschamps (Fig. 89) and of Fange and Chavanon (Fig. +90), on the other hand, are producers in which the combustion is really +inverted, and which are worked continuously. The air enters at the upper +part of the retort, passes through the entire mass of fuel, carrying +with it the distilled volatile products, and when the mixture reaches +the incandescent zone, chemical reactions occur that result in the +production of a gas entirely free from tar and other impurities. + + + + + CHAPTER XIII + + SUCTION GAS-PRODUCERS + + +The high cost and the complicated nature of the pressure gas-generators +which have just been discussed have led manufacturers to attempt in some +other way the generation of producer-gas intended for operating motors. + +Several inventors, among whom we will mention Benier and A. Taylor (in +France), made some praiseworthy although not immediately very successful +attempts to simplify the manufacture of producer-gas. + +=Advantages.=--In these systems the suction occasioned by the motor +itself has taken the place of a forced draft, produced in the generator +by an air-injector or a fan, so that the gas, instead of being stored +under pressure in a gas-holder, is kept in the apparatus under a +pressure below that of the atmosphere. + +As the device for producing a draft by means of boiler pressure or of a +fan, and the gas-holder, are dispensed with, the result is a saving, +first in the cost of installation, consumption, and floor space. +Furthermore, the cooler and washer are supplanted by a single scrubber. + +Manufacturers have succeeded in devising apparatus remarkable for the +simplicity of the processes employed and yielding economical results +which would never be obtained with pressure-generators employing +gas-holders and boilers, considering that the boiler alone calls for a +consumption of from 15 to 30 per cent. of the total amount of coal used +for making the gas. + +The best results obtained by the author with pressure gas-producers have +indicated a consumption of not much less than 1 to 1-1/4 pounds of +anthracite per horse-power per hour at the motor, while with +suction-generators, under similar conditions and with the same grade of +fuel, he has repeatedly found a consumption of from 9/10 pounds per +effective horse-power per hour. In either case, the gas obtained +developed between 1,100 and 1,300 calories (4,365 and 5,158 B.T.U. per +35.31 cubic feet) if produced from anthracite yielding from 7,500 to +8,000 calories (29,763 to 31,746 B.T.U.) per 2.2 pounds. + +The suction apparatus will also work very well with inferior coal +containing up to 6 to 8 per cent. of volatile matter and from 8 to 10 +per cent. of ash. This great advantage added to all the others explains +the favorable reception which European manufacturers at once gave to +suction-producers. The petroleum engine itself will find a serious +competitor in the new system. + +As regards the possibility of employing suction gas generators with +respect to the somewhat peculiar properties of the fuel, it may be said +at the outset that coke from gas works yielding from 6,000 to 6,500 +calories (22,911 to 24,995 B.T.U.) and also charcoal are perfectly +available. + +One horse-power per hour is obtained with a consumption of 1.1 to 1.3 +pounds of coke. + +Blast-furnace coke may be used in case of need, but its employment is +not to be recommended on account of the sulphides it contains, which +sulphides, being carried along by the gas, are liable to form sulphuric +acid with the steam, the corrosive action of which would soon destroy +the cylinder and other important parts of the engine. + +=Qualities of Fuel.=--Anthracite coal is, upon the whole, so far the +best available fuel for generators. However, it should possess certain +qualities which will now be briefly indicated. + +In suction gas-generators, above all, it is important that no harmful +resistance should be opposed to the passage of the air and of the gas +produced. It is therefore necessary to employ coal of a size that will +answer the foregoing condition, without being too expensive. + +The size of the pieces, to a certain extent, determines the price; and +with coal of the same properties, pieces 1.1 to 2 inches may cost 1.4 of +the price for the ordinary size of 0.59 to 0.98 inches, which is very +well adapted for gas-generators. This is the size of a hazel-nut. + +Moreover, it will be advisable to select the dryest coals, containing a +minimum of volatile matter and having no tendency to coke or to cohere, +in order that the volatilized products may not by distillation obstruct +the interstices through which the gases must pass. For the same reason +coal which breaks up and becomes pulverized under the action of the +fire is not to be recommended. The coal should also be such as to avoid +the formation of arches which would interfere with the proper settling +of the fuel during its combustion. It may be stated as a rule that, with +coal that does not cohere, the content of volatile matter should not +exceed 5 to 8 per cent. + +Coal which contains more than 10 to 15 per cent. of ash should not be +used, for the reason that it chokes up and obstructs generators in which +the dropping and discharge of the ashes is done automatically, a fact +which should not pass unnoticed. The furnace cannot be cleaned safely +with a fire of this kind, where combustion takes place in an enclosed +space, without hindering the production of gas. Here again a point may +be raised very much in favor of suction gas-producers. In a good +generator, the ash-pit can be cleaned and the fire stoked without +interrupting the liberation of the gas drawn in and without appreciably +impairing the quality of the gas. These considerations are of importance +so far as the gas-generator itself is concerned. Other conditions which +should be noticed affect the engine fed by the generator, the grade of +coal used, and the purification of the gas obtained from it. + +Unless special chemical cleaners and purifiers are employed, thereby +complicating the plant, the coal utilized should yield as little tar as +possible during distillation; for the tendency of the tar to choke up +the pipes and to clog the valves is one of the chief causes of defective +operation of producer-gas engines. + +Tar changes the proper composition of the explosive mixture. When it +catches fire in the cylinder it causes premature ignition, which is so +dangerous in large engines. + +From what has been said in the foregoing, it follows that, in the +present state of the art, the satisfactory operation of gas-generators +depends no longer on the use of pure anthracite, such as Pennsylvania +coal in America and Welsh coal in England, containing an amount of +carbon as high as 90 to 94 per cent. and having a thermal value of +33,529 B.T.U. On the contrary, good dry coal yielding from 29,763 to +31,746 B.T.U. is quite suitable for the generation of producer-gas. + +A final, practical advantage which speaks in favor of a generator and +motor plant as compared with a steam-engine, is the small amount of +water required. Apart from the water used for cooling the engine, which +may be used over and over again if cooled, any water, whether it forms +scale or deposits, may be employed for cooling and washing the gas in +the scrubber. + +According to the author's personal experience, an average of 3.3 gallons +of water per effective horse-power per hour is sufficient for this +purpose. This is about one-half of the amount required by a +non-condensing slide-valve engine of from 15 to 30 horse-power. The +difference in the consumption of water is quite important in city +plants, where water is rather expensive as a rule. + +=General Arrangement.=--A suction gas-generator plant of the character +we have been discussing is shown in Fig. 91. + +[Illustration: FIG. 91.--Engine and suction gas-producer.] + +The apparatus _A_ is the generator proper, in which combustion takes +place. The gas produced passes into the apparatus _B_ through a series +of tubes, to be conveyed to the washer _C_. In the apparatus _B_, which +is the vaporizer, the water admitted at the top under atmospheric +pressure is vaporized by contact with a series of tubes, heated by the +gas coming from the generator. The steam, together with air, is drawn +into the lower part of the generator to support combustion. This +vaporizer is provided with an overflow for the outlet of the water which +has not been vaporized. The producer-gas pipe which leads from the +vaporizer to the washer has a branch _D_, for the temporary escape to +the atmosphere of the gas produced before and after the operation of the +engine. In the washer, as the drawing shows, the gas enters at the +bottom and leaves at the top to pass to the gas expansion-chamber _E_ +and thence to the motor. The gas thus passes through the body of coke +in the opposite direction to the wash water, which then flows to the +waste-pipe. The coke and the water free the gas not only from the dust +carried along, but from the ammonia and other impurities contained in +the gas. + +When firing the generator, a small hand ventilator _G_ is used for +blowing in air to fan the fire. The gas obtained at first, being +unsuitable for combustion, is allowed to escape through the branch _D_. +After injecting air for about 10 to 15 minutes, the engine can be +started after closing the branch _D_. The suction of the engine itself +will then gradually bring about the proper conditions for its regular +running, and after a quarter of an hour or half an hour the gas is rich +enough to run the engine under a full load. + +The apparatus just described is the original type, upon which many +improvements have been made for the purpose of securing a uniform gas +production and of diminishing the interval of time elapsing between the +firing of the generator and the running of the engine under a full load. + +Each of the elements of this apparatus--to wit, the generator, +vaporizer, super-heater, and washer--have been modified and improved +more or less successfully by the manufacturers; and in order that the +reader may perceive the merits and the drawbacks of the various +arrangements adopted, the most important ones will be separately +discussed. + +=Generator.=--With respect to the general arrangement of parts, +generators may be divided into two classes: + +First.--Generators with internal vaporizers, such as the Otto Deutz and +Wiedenfeld generators. + +[Illustration: FIG. 92.--Old type of Winterthur producer.] + +Second.--Generators with external vaporizers, such as the Taylor, +Bollinckx, Pintsch, Kinderlen, Benz, Wiedenfeld, Hille, and Goebels +generators. + +=Cylindrical Body.=--The generator consists essentially of a mantle made +of sheet-iron or cast-iron and containing a refractory lining which +forms a retort, a grate, and an ash-pit. In the small size apparatus the +cast-iron mantle is often used, whereas in large sizes the mantle is +made of riveted sheet-iron so as to reduce its weight and its cost. In +the latter case the linings are securely riveted or bolted. + +The Winterthur generator (Figs. 92 and 93), the Taylor generator (Fig. +94), and the Benz generator (Fig. 97), are made of cast-iron; the +Wiedenfeld generator (Fig. 95), the Pintsch generator (Fig. 96), are +made of sheet-iron; the Bollinckx (Fig. 98) is made partly of sheet-iron +and partly of cast-iron. + +The different parts of a generator, if made of sheet-iron, are held +together by means of angle-irons forming yokes, and a sheet of asbestos +is interposed. If the parts are made of cast-iron, they are connected +after the manner of pipe-joints and packed with compressed asbestos. +This latter way of assembling the parts presents the advantage of +allowing them to be dismembered readily. Therefore, it allows the +several parts to expand freely and facilitates the securing of tight +joints. This last consideration is exceedingly important, particularly +for the joints which are beyond the zone in which the distillation of +the fuel takes place. Any entrance of air through these joints would +necessarily impair the quality of the gas, either by mingling therewith, +or by combustion. The air so admitted would also be liable to form an +explosive mixture which might become ignited in case of a premature +ignition of the cylinder charge during suction or through some other +cause. + +[Illustration: FIG. 93.--New type of Winterthur producer.] + +[Illustration: FIG. 94.--The A. Taylor producer.] + +[Illustration: FIG. 95.--Wiedenfeld producer.] + +[Illustration: FIG. 96.--Pintsch producer.] + +[Illustration: FIG. 97.--Benz producer.] + +[Illustration: FIG. 98.--Bollinckx producer.] + +[Illustration: FIG. 99.--Lencauchez producer.] + +=Refractory Lining.=--The interior lining of the generator should be +made of refractory clay of the best quality. It would seem advisable, in +order to facilitate repairs, to employ retorts made of pieces held +together instead of retorts made of a single piece. In the first case +the assembling should preferably be made by means of refractory cement, +and the inner surface should be covered with a coating so as to form a +practically continuous stone surface. + +[Illustration: FIG. 100.--Goebels producer.] + +Some manufacturers, in order to allow for the renewal of the part most +liable to be burnt, employ at the bottom of the tank a refractory +moulded ring (Lencauchez, Fig. 99). + +It is always advisable to place between the shell or mantle of the +generator and the refractory lining a layer of a material which is a bad +conductor of heat as, for instance, asbestos or sand, in order to avoid +as much as possible loss of heat due to external radiation (Fig. 100). + +[Illustration: FIG. 101.--Pierson producer.] + +=Grate and Support for the Lining.=--These parts, owing to their contact +with the ashes and the hot embers, are liable to deteriorate rapidly. It +is therefore indispensable that they should be removable and easily +accessible, so that they may be renewed in case of need. From this point +of view, grates composed of independent bars would appear to be +preferable. The clearance between the bars depends, of course, on the +kind of ashes resulting from the different grades of fuel. It is +advisable to design the grate so that the free passage for the air is +about 60 to 70 per cent. of the total surface. + +In generators having a cup-shaped ash-pit, containing water (Fig. 95), +the grate and the base of the retort are less liable to burn than in +apparatus having dry ash-pits. Certain apparatus, such as those of +Lencauchez (Fig. 99), Pierson (Fig. 101), and Taylor (Fig. 94), have no +grates; the fuel is held in the retort by the ashes, which form a cone +resting on a sheet-iron base, easy of access for cleaning and from which +the fuel slides down gradually. + +The Pierson generator (Fig. 101) is provided with a poker comprising a +central fork, which is worked with a lever, in order to stir the fire +from below without entirely extinguishing the cone of ashes. + +In some apparatus in which a grate is used (Fig. 92), a space is left +between the grate and the support of the retort. This arrangement has +the merit of allowing only finely divided and completely burnt ashes to +pass to the ash-pit. Moreover, a large surface grate can be employed, +thus facilitating the passage of the mixture of air and steam. + +[Illustration: FIG. 102.--Kiderlen producer.] + +The space above mentioned is provided with a cleaning-door through which +cinder and slag may be removed. + +In other apparatus the grate rests either on the support of the +refractory lining, as in the old type invented by Wiedenfeld (Fig. 95), +or upon a projection embedded in the lining, as, for instance, in the +Kiderlen (Fig. 102) and Pintsch generators (Fig. 96). + +In the Riche apparatus (Fig. 103) there is, besides the ordinary grate, +a grate with tiers on which the fuel spreads. This grate consists of +wide, hollow bars containing water. It should be noted that the +apparatus is of the blower type. + +[Illustration: FIG. 103.--Riche combustion-producer.] + +An interesting arrangement is found in Benier's generator (Fig. 104). +This consists of a grate formed of projections cast around a cylinder +which can be turned about its axis. The finely divided ashes which are +retained in the spaces between these projections are thus carried into the +ash-pit, and those which adhere to the metal are scraped away by a +metallic comb fastened to the lower part of the apparatus. The "Phoenix" +generator (Fig. 105) is fitted with a grate having a mechanical cleaning +device, worked by a lever from the outside. + +[Illustration: FIG. 104.--Benier producer.] + +[Illustration: FIG. 105.--Phoenix producer.] + +=Ash-Pit.=--The ash-pits are exposed to the destructive effects of +heat and moisture, and should preferably be constructed of cast-iron, +since sheet-steel is liable to corrode quickly. + +[Illustration: FIG. 106.--Otto Deutz producer.] + +In most apparatus the ash-pit is hermetically sealed, and the air for +supporting combustion enters below the grate through a pipe leading +from the heater or the vaporizer. This arrangement seems best adapted to +prevent the leakage of gas which tends to take place by reaction after +each suction stroke of the engine. + +Ash-pits formed as water-cups, such as the Deutz (Fig. 106), the +Wiedenfeld (Fig. 95), and the Bollinckx (Fig. 98), are fed by the +overflow from the vaporizer. These ash-pits are themselves provided with +an overflow consisting of a siphon-tube forming a water-seal. + +Besides providing protection to the grate and other parts by this sheet +of water, a larger proportion of the heat radiated from the furnace is +utilized for the production of steam which contributes to enrich the +gas. The doors of the ash-pits and their fittings are likewise exposed +to a rapid deterioration. + +For this reason these parts should be very strongly made, either of +cast-iron or cast-steel. Furthermore, they should, at joint surfaces, be +connected in an air-tight manner, which may be attained by carefully +finishing the engaging surfaces of the frame and the door proper, or by +cutting a dovetail groove in one of the sides of the frame which is +packed with asbestos and adapted to receive a sharp edged rib on the +other part. + +The pintles of the hinges should also be carefully adjusted so that the +joint members of the door shall remain true. Hinges with horizontal axes +seem to be preferable in this respect to those having vertical axes. As +a means of closing the door, the arrangement here shown (Fig. 107) seems +to assure a proper engagement of the joint surfaces. It consists of a +yoke which straddles the door, and which, on the one hand, swings about +the hinge, and on the other hand engages a movable hoop. A screw, +fastened to the yoke, serves to tighten the door by pressure on its +center. This screw can also be fastened to the end of the yoke (Fig. +108). + +[Illustration: FIGS. 107-108.--Fire-box doors.] + +It is very advantageous to provide in each door a hole closed by an +air-tight plug, so that in case of need a tool may be introduced for +cleaning the grate. In this manner the grate may be cleaned without +opening doors and without causing a harmful entrance of air. + +The door of the furnace, particularly, should be provided with an iron +counter-plate held by hinged bolts (Fig. 109); or, better still, this +door should be so constructed that it can be lined with refractory +material to protect it against the radiated heat of the fire. + +=Charging-Box.=--Like the other parts of the generator the construction +of which has been discussed above, the charging-box should be absolutely +air-tight. + +On account of their greater security, preference should be given to +double closure devices, which form a sort of preliminary chamber, owing +to which the filling of the generator is made in two operations. The +first operation consists in filling the preliminary chamber after +opening the outer door. Upon closing this outer door, the second +operation is performed, which consists in moving the inner door so as to +cause the fuel in the preliminary chamber to drop into the generator. +Stress has been laid on the greater safety of this type of charging-box +for the reason that, with devices having a single charging-door, a +sudden gust of air may rush in at the time of charging the furnace, and +bring about an explosion very dangerous to the workman entrusted with +stoking the furnace. + +[Illustration: FIG. 109.--Door with refractory lining.] + +The closure is generally simply a removable cover, or may be a lid +swinging about a hinge having a horizontal or vertical axis. + +As regards the inner door, which is of great importance, in order to +insure an air-tight joint, there are three chief types of closure: + +1. The Lift-Valve. +2. The Slide-Valve. +3. The Cock. + +=The Lift-Valve.=--The lift-valve is formed by a disk of conical or +spherical shape moved up and down by means of a lever having a +counter-weight for adjustment. The valve is used in the Winterthur (Fig. +92) and Bollinckx (Fig. 98) generators. + +This device serves as an automatic closure and insures a tight joint +irrespective of wear. Moreover, it presents the advantage that, at the +moment of opening, it distributes the fuel evenly in the generator; but +on the other hand, it has the drawback of not allowing the fuel to be +examined or shaken through the charging-box. In apparatus provided with +this kind of valve, it is therefore advisable to furnish the upper part +of the generator with agitating holes closed by an air-tight slide. + +=Slide-Valve.=--The slide-valve closure consists of a smooth-finished +metallic plate movable below the charging-box proper. Operated as it is +from the outside, it is evident that the slightest play, the wearing of +the pivot, or the weight of the charge, will form spaces between the +plate and its seat through which air may rush in. + +Furthermore, the manipulation of the slide-valve may be interfered with +if too much fuel is put in the generator. + +The valve or damper may move parallel to itself or swing about the +operating axis. The Taylor apparatus (Fig. 94) and the Benier apparatus +(Fig. 104) are provided with such valves. + +The Pintsch generator (Fig. 96) is provided with a device which, +properly speaking, is not a damper, but which consists of two boxes +movable about a vertical axis and arranged to be displaced alternately +above the shaft to effect the charging. This system effects only a +single closure, but explosions are scarcely to be feared with an +apparatus of this kind, owing to the considerable height of fuel +contained between the charging opening and the gas-producing zone. + +=Cock.=--The cock is applied particularly in the modern apparatus of the +Otto Deutz Co. (Fig. 106) and the Pierson generator (Fig. 101). It +consists of a large cast-iron cone, having an operating handle and an +opening. The cone moves in a sleeve formed by the charging-box. + +This arrangement appears to be preferable to the others on account of +its simplicity and of the ease with which it can be taken apart for +cleaning. Moreover, the fuel can be poked directly through the +feed-hopper. In apparatus provided with a cock, it is advisable to place +on the outside cover a mica pane through which the condition of the fuel +may be examined without danger. + +=Feed-Hopper.=--Below the charging-box is arranged, as a rule, a hopper +tapered conically downward. This part of the generator should serve only +as a storage chamber for fuel. It can therefore be made of cast-iron, +and has the advantage of being removable, easily replaced, and of +allowing ready access to the retort for the purposes of examination and +repair. + +The annular space surrounding this feed-hopper generally forms a chamber +for receiving the gas produced, as in the Winterthur (Fig. 92), the +Bollinckx (Fig. 98), and the Taylor apparatus (Fig. 99). + +In generators having an internal vaporizing-tank, this tank itself +serves as a feed-hopper, which is the case in the Deutz apparatus (Fig. +106) and Wiedenfeld generator (Fig. 95). + +=Connection of Parts.=--In order to facilitate the thorough cleaning of +the retort, preference is given to removable charging-boxes and +feed-hoppers. These are features of apparatus of the Bollinckx type +(Fig. 98), in which the charging-box is secured to the generator by +means of its yoke and by catches provided with knobs, and also of +apparatus of the Winterthur kind (Fig. 92), having a charging-box +pivoted about a vertical axis, or apparatus of the Duplex type (Fig. +110), in which the charging-box can swing about a horizontal hinge. + +=Air Supply.=--We have seen that, when starting the generator, the gas +is produced with the aid of a fan. This fan may be operated +mechanically, but is generally operated by hand. + +It is customary to convey the air-blast through a pipe leading to the +ash-pit, as in the Winterthur apparatus (Fig. 92). Often, however, the +air supply pipe is directly branched on that which leads from the +vaporizer to the ash-pit, as in the Deutz apparatus (Fig. 106). In this +case a set of valves or dampers permits the disconnection of the fan or +its connection with the ash-pit. + +[Illustration: FIG. 110.--Duplex charging-hopper.] + +In some apparatus an air inlet is provided immediately adjacent to the +ash-pit. This arrangement is faulty for the reason that it gives rise to +gaseous emanations which take place by reaction after each suction +stroke of the engine. Furthermore, it is advisable that the air supplied +below the ash-pit be as hot as possible. For this reason the employment +of preheaters is desirable. The dry air forced in by the fan stimulates +combustion, and the hot gas produced and mixed with smoke escapes +through a separate flue, generally arranged beyond the vaporizer and +serving as a chimney. This chimney should in all cases be extended to +the outside of the building, and should never terminate in a brick +chimney or similar smoke-flue. The direct escape of such gas and smoke +through a telescopic chimney above the charging-box has been generally +abandoned in modern structures. + +[Illustration: FIG. 111.--Bollinckx flue and scrubber.] + +[Illustration: FIG. 112.--Winterthur flue and air-reheater.] + +The escape-pipe mentioned, being branched on the gas-pipe leading to the +engine, should be capable of disconnection when desired, by a thoroughly +tight system of closure. For this purpose, some employ a simple cock +(Bollinckx, Fig. 111), a three-way cock, a set of cocks, or, still +better, a double valve, as in the Winterthur apparatus (Fig. 112) and +the Deutz apparatus (Fig. 113). A double seated valve is also used, as +is the case in the Benz generator (Fig. 114). + +[Illustration: FIG. 113.--Otto Deutz flue.] + +[Illustration: FIG. 114.--Benz flue.] + +=Vaporizer-Preheaters.=--As has been stated before, there are vaporizers +internal or external, relatively to the generator. + +=Internal Vaporizers.=--The Deutz apparatus (Fig. 106), for example, +consists of an annular cast-iron tank mounted above the retort of the +generator. + +The hot gases given off by the burning fuel travel around this tank and +vaporize the water which it contains. The air drawn in by the suction of +the engine enters through an opening located above the tank, travels +over the surface of the water which is being vaporized, and thus laden +with steam passes to the ash-pit. + +The tank in question is supplied with water by means of a cock having a +sight feed, located on the outside, and the level is kept constant by +means of an overflow tube leading to the ash-pit. It is well to bend +this tube and to place a funnel on its lower member. The amount of +overflow may thus be regulated. + +These vaporizers are simple and take up little room; but they are open +to the apparently well-founded objection that they heat up slowly and +require a considerable time to produce the steam necessary to enrich the +gas, this being due to the relatively large mass of cast-iron and the +amount of water contained therein. + +The Pierson vaporizer (Fig. 101) and the Chavanon vaporizer (Fig. 115) +both consist of an annular tank forming the base of the generator. Steam +is formed near the outlet of the ashes, which, as has been described +above, leads to the outer air. The development of steam is regulated by +mechanical means controlled by the suction of the engine. + +[Illustration: FIG. 115.--Chavanon producer.] + +=External Vaporizers.=--External vaporizers are generally formed by a +cylinder with partitions constituting two series of chambers. In one of +these the hot gases from the generator travel, and in the others the +water to be vaporized is contained. + +[Illustration: FIG. 116.--Taylor vaporizer.] + +[Illustration: FIG. 117.--Deutz vaporizer.] + +=Tubular Vaporizers.=--Different types of tubular vaporizers are +manufactured. The vaporizer with a series of tubes, as in Taylor's +apparatus (Fig. 116), Deutz's old model (Fig. 117), or with single tube +like Pintsch's generator (Fig. 118), is formed by three compartments +separated by two tube sheets or by plates which are connected by tubes. + +In some cases the gases pass within the tubes, while the water to be +vaporized surrounds them; as in the Pintsch apparatus (Fig. 118), and +Taylor apparatus (Fig. 116), Benz (Fig. 119), and Koerting generators +(Fig. 120). + +[Illustration: FIG. 118.--Pintsch vaporizer and scrubber.] + +In other cases, the water lies inside and the gas outside. In this +latter case, a longitudinal baffle is employed to compel the gases to +heat the tubes in their whole length, as in the Deutz producer (Fig. +117). In a general way it may be said that such a series of tubes +presents the disadvantage of becoming clogged up rapidly by the deposit +of lime salts contained in water. + +[Illustration: FIG. 119.--Benz vaporizer.] + +[Illustration: FIG. 120.--Koerting vaporizer.] + +If the set of tubes consists of fire-tubes, the deposit will form on the +outer surface, that is, on a portion not accessible for cleaning. From +this point of view, water-tubes are preferable, as they allow the +deposit or scale to be removed through the tubular heads or plates. On +the other hand, such water-tubes have the drawback that their exterior +surfaces are readily covered with pitch and soot. The tubular vaporizers +of the Field type (Bollinckx, Fig. 98) are composed of a single +sheet-iron tube or shell, in which the tubes are arranged, dipping into +a chamber through which the hot gases pass. This arrangement insures a +rapid production of steam, but the Field tubes are even more liable than +the others to become covered with deposits. + +It will be seen that these types of vaporizers should all present the +following features: easy access, small quantity of the body of water +undergoing vaporization, and large heating surface with small volume. + +The use of copper or brass tubes should be strictly avoided, as they +would be quickly corroded by the action of the ammonia and hydrogen +sulphide contained in the gas. + +=Partition Vaporizers.=--Partition vaporizers comprise a cylindrical +shell, generally made of cast-iron and having a double wall in which the +water to be vaporized circulates. The gas coming from the generator +passes into the central portion, where it comes in contact with a hollow +baffle, also containing water (Wiedenfeld, Fig. 121). Vaporizers of this +kind are strong, simple, and easily cleaned. + +=Operation of the Vaporizers.=--The general purpose of vaporizers, +whatever their construction may be, is to produce steam under +atmospheric pressure, by utilizing the heat of the generator gases +immediately after their production, or, as in the Chavanon system, by +utilizing the heat radiated from the furnace. + +The air drawn by the engine through the generator generally passes +through the vaporizers and becomes laden with a certain amount of steam +which it carries along. The amount thus taken up depends chiefly upon +the temperature and the amount of gases coming from the generator, so +that the greater the amount drawn into the engine, the more energetic +will the vaporization be, and the richer the gas will become. It will be +understood that when a generator is working at its maximum production, +the interior temperature is highest and most favorable to the +decomposition of the largest amount of steam. + +[Illustration: FIG. 121.--Wiedenfeld vaporizer.] + +It follows that with the very simple vaporizers which have been +reviewed, a practically automatic regulation is obtained. However, some +manufacturers have deemed it advisable to regulate the amount of steam +more accurately, and to make it exactly proportionate to the power +developed by the motor. Thus in the Winterthur gas-producer (Figs. 92 +and 112) the manufacturers have omitted the vaporizer proper, and use +instead an air-heater and a super-heater for air and steam. + +The heater is formed by a cast-iron box having two compartments, through +one of which the hot gases from the generator pass, while in the other +the air intended to support combustion travels. At the inlet of the +super-heater a pipe terminates, which feeds, drop by drop, water +supplied by a feed device to be described presently. This water is +vaporized immediately upon contact with the wall of the super-heater and +is carried along with the air contained in it. + +The super-heater comprises a hollow ring-shaped cast-iron piece arranged +in the chamber of the generator, in which the gases are developed, and +is thus heated to a high temperature. The mixture of air and steam +circulates in this super-heater before traveling to the ash-pit. + +The feeder of the Winterthur gas-generator (Fig. 122) is composed of a +receptacle having the shape of a tank or basin containing water and +located below a closed cylindrical box. In this box a piston moves, +which is provided at its lower end with a needle-valve. The upper +portion of the box communicates with the gas-suction pipe through a +small tube. At each suction stroke of the engine, according to the force +of the suction, the needle-valve piston rises more or less and thus +allows a variable amount of water to pass. + +[Illustration: FIG. 122.--Winterthur feeders.] + +This apparatus--and all those based on the same principle--presents the +advantage of proportioning the amount of water to the work of the +engine; but in view of its rather sensitive operation it must be kept in +perfect repair and carefully watched. Obviously, should the water +contain impurities, the needle-valve will bind or the orifices will be +obstructed, and thus the feeding of the water will be interrupted. This +will not only result in the production of a poorer gas, but will lead to +greater wear of the grates, which in this case are not sufficiently +cooled by the introduction of steam. + +[Illustration: FIG. 123.--Hille producer.] + +=Air-Heaters.=--The preliminary heating of the air appears to be of +great utility for keeping up a good fire. This heating is very easily +accomplished, and is generally effected by utilizing a portion of the +waste heat of the gases, a procedure which also has the advantage of +cooling the gases before they pass through the washing apparatus. + +The heating of the air for supporting combustion takes place either +before the addition of steam (Hille's generator, Fig. 123), or after the +mixture as in Wiedenfeld's apparatus (Fig. 95). In the first case, the +air passes through a sheet-iron shell concentric with the basin of the +generator, is there heated by the radiated heat, and is conveyed to the +ash-pit by a tube into which leads the steam-supply pipe extended from +the vaporizer. In the second type of heater, the mixture of air and +steam is super-heated during its passage through an annular piece +arranged in the ash-pit of the generator. + +[Illustration: FIG. 124.--Benz dust-collector.] + +=Dust-Collectors.=--Dust-collectors are generally placed between the +generator and the scrubber or washer. They may be formed of baffle-board +arrangements against which the gases laden with dust impinge, causing +the dust to be thrown down into a box provided with a cleaning opening +(Benz, Fig. 124, and Pintsch, Fig. 118). + +Some collectors are formed either by the vaporizer itself, terminating +at its base in a tube which dips into water and forms a water-seal, as +in the Wiedenfeld generator (Fig. 121), or by a water-chamber into which +the gas-supply tube slightly dips (Bollinckx, Fig. 111). With this +arrangement, the gas will bubble through the water and will be partly +freed of the dust suspended in it. These water-chambers are generally +fed by the overflow from the spray of the scrubber. There is thus +produced a continuous circulation by which the dust, in the form of +slime, is carried toward the waste-pipe or sewer. + +=Cooler, Washer, Scrubber.=--Some manufacturers cool the gas in a tower +with water circulation. Most manufacturers, however, simply cool the gas +in the washer or scrubber. This apparatus comprises a cylindrical body +of sheet-iron or cast-iron formed of two compartments separated by a +wooden or iron grate or perforated partition. The upper compartment up +to a certain level contains either coke, glass balls, stones, pieces of +wood, and the like. The top of the compartment is provided with a water +supply in the nature of a sprinkler or spray nozzle. The lower +compartment of the scrubber serves to collect the wash-water which has +passed through the substance filling the tower. An overflow in the shape +of a siphon, provided with a water seal, carries the water to the +waste-pipe either directly or after it has first passed through the dust +collector. + +The gas drawn in enters the washer in the lower compartment either above +the water level (Deutz, Fig. 125; Winterthur, Fig. 126), or through an +elbow which dips slightly into the water (Benz, Fig. 127; Fichet and +Heurtey producer, Fig. 128). + +The gas passes through the grate or partition which supports the +material filling the tower, and travels through the interstices in a +direction opposite to that of the water falling from the top. Under +these conditions, the gas is cooled, gives up the ammonia and the dust +which it may still contain in suspension, and is conveyed to the engine +either directly or after passing through certain purifiers. Care should +be taken to place the pieces of most regular shape along the walls, so +that the unevenness of their surfaces may not form upward channels along +the shell, through which channels the gas could pass without meeting the +wash-water. + +[Illustration: FIG. 125.--Otto Deutz scrubber.] + +[Illustration: FIG. 126.--Winterthur scrubber.] + +[Illustration: FIG. 127.--Benz scrubber.] + +The material most commonly employed in washers is coke in pieces of from +2-1/2 to 3-1/2 inches in size. This material is cheap and is very well +suited for retaining the impurities of the gas. The largest pieces of +coke should be placed at the bottom of the washer, and smaller pieces +should form at the top a layer from 6 to 8 inches deep. In this manner +the water is distributed more evenly and the gas is more thoroughly +washed. Blast-furnace coke is best suited for this washing, as it is +more porous and less brittle than gas-works coke. It is advisable to +put a baffle-board in front of the gas outlet to reduce the carrying +along of water in the conduits. + +[Illustration: FIG. 128.--Fichet-Heurtey scrubber.] + +[Illustration: FIG. 129.--Scrubber-doors.] + +The tower of the washer should be provided with three openings having +air-tight closures, easily fastened by screws (Fig. 129). One of the +openings is located in the lower compartment, slightly above the water +level, to allow the deposits to be removed and to permit the cleaning of +the orifice of the gas-supply tube, which is particularly liable to be +obstructed. The second opening is placed above the grating which +supports the filtering material. The third opening is provided on the +top of the apparatus to permit the examination and cleaning of the water +feed device and the gas outlet without the necessity of taking the lid +of the washer apart, the joint of which is kept tight with difficulty. +The two openings last mentioned also serve for introducing and removing +the filtering material. + +=Purifying Apparatus.=--In some cases, where it is necessary to have +very clean gas or where coal is employed which is softer than anthracite +coal, and which therefore produces an appreciable amount of tar, +supplementary purifying means must be employed. The apparatus for this +purpose may, like the washers, be based upon a physical action or upon a +chemical action. The physical action has for its purpose chiefly to +retain the pitch and the dust which may have passed through the washer. + +This is accomplished by means of sawdust or wood shavings arranged in a +thin layer and capable of filtering the gas without opposing too great +a resistance to its passage. These materials are spread on one or more +shelves superposed to form successive compartments in a box closed in an +air-tight manner by an ordinary lid or a water seal cover (Pintsch, Fig. +130; Fichet and Heurtey, Fig. 131). It may be well to point out that the +presence of the water carried along will, in the end, destroy the +efficiency of the precipitated materials, because they swell up and +cease to be permeable to the gas. These materials must therefore be +renewed rather frequently. To obviate this drawback, vegetable moss may +be employed, which is much less affected by moisture than most filters +and keeps its spongy condition for a long time. + +[Illustration: FIG. 130.--Pintsch purifier.] + +The chemical action has for its chief object to rid the gas of the +carbonic acid and the hydrogen sulphide which certain fuels give off in +appreciable amounts. The purifying material, in this case, is formed +either by a mixture of hydrate of lime and natural iron oxide, or by the +so-called Laming mass, which consists of iron sulphide, slaked lime, and +sawdust, which last serves the purpose of rendering the material looser +and more permeable to the gas. The Laming mass as well as other +purifying materials will become exhausted in the course of chemical +reactions. It can be regenerated merely by exposure to the air. + +[Illustration: FIG. 131.--Fichet-Heurtey purifier.] + +=Gas-Holders.=--The purifiers by themselves constitute, to a certain +extent, storage chambers for the gas before it is supplied to the +engine; but in plants for the generation of gas without purifiers it is +advisable to provide a gas-holder on the suction conduit near the +engine. + +[Illustration: FIG. 132.--Pintsch regulating-bell.] + +In order to save floor space the gas-holder may be placed in the +basement. Preferably the capacity of the holder should be at least from +3 to 4 times the volume of the engine-cylinder. The holder should also +be provided with a drain-cock and with a hand-hole located at some +accessible point, so that the slimes and pitch which tend to accumulate +in the holder can be removed. In some cases the gas-holder is formed by +a small regulating bell, the function of which is to insure a uniform +pressure. This bell is emptied during the suction period and is filled +during the three succeeding periods of compression, explosion, and +exhaust (Pintsch, Fig. 132). + +[Illustration: FIG. 133.--Types of gas-driers.] + +=Drier.=--Sometimes, toward the end of a producer-gas pipe, a drier is +located for the purpose of keeping back the water carried along, the +drier being similar to that employed in steam conduits. It will, of +course, be understood that such driers are useful only in plants having +no purifiers (Fig. 133). The employment of the drier is advisable to +prevent the entrance of moist gas into the cylinder and the condensation +of moisture on the electric igniter. + +[Illustration: FIG. 134.--Elbow with closure.] + +=Pipes.=--The pipes connecting the several parts of a gas-producing +plant should be disposed with particular care to insure tightness and +cleanliness. It should be borne in mind that the gas is under a pressure +below that of the atmosphere, and that the least leakage will cause the +entrance of air, which will impair the quality of the gas. The greatest +care should therefore be taken in fitting the joints. These joints are +numerous, because there are joints wherever tubes are connected with +each other and with the apparatus. Furthermore, all elbows should be +provided with covers held in place by a yoke and compression screw, this +being done for the purpose of providing for the introduction of a brush +or other implement to remove the dust and pitch (Fig. 134). + +For conduits of small diameter the elbows with covers may be replaced +with =T= connections, or connections provided with plugs. + +Gas piping in the immediate neighborhood of the cock for admitting gas +to the motor should be provided with a conduit of proper diameter +leading to the open air and serving to clean the apparatus and to fill +them, during the operation of the fan, with gas suitable for combustion. +This conduit should be provided with a stop-cock. Test-cocks for the gas +should be placed on the piping immediately beyond the vaporizers, the +scrubber, and near the engine. + +It will also be well to provide water-pressure gages before and after +the scrubber to enable the attendant to ascertain the vacuum in the +conduits and to adjust the running of the apparatus. + +=Purifying-Brush.=--As an additional precaution against the carrying of +tar to the engine, metallic brushes are often employed, these brushes +being spiral in form and enclosed in a cast-iron box interposed in the +gas-supply pipe immediately after the engine. The gas will be broken up +into streams by the obstacles formed by these brushes and will be freed +of the suspended tar (Fig. 135). These brushes should be carefully +cleaned at regular intervals. The best way of doing this is to drop them +into kerosene or some other suitable solvent. + +[Illustration: FIG. 135.--Metal purifying-brush.] + + + CONDITIONS OF PERFECT OPERATION OF GAS-PRODUCERS + +These conditions depend upon the workmanship or upon the system of the +plant, on the care with which it has been erected, on the nature of the +fuel, on the condition of preservation of the apparatus, and upon the +manner in which the producers have been working. + +=Workmanship and System.=--The workmanship itself, which term is meant +to include the choice of materials and the way they have been worked, +presents no difficulty. The producers which we have discussed are very +simple and offer absolutely no difficulties in their mechanical +execution. As regards the system, however, especially with respect to +the relative dimensions of the elements, it does not seem so far that it +is possible to indicate any principle or rule capable of a rigid general +application. It must be taken into account that the use of suction +gas-generators has become general only in the last three or four years; +the problem has therefore scarcely been adequately solved. However, some +hints may be given on this subject. + +=Generator.=--In regard to the generator, it is possible to deduce from +the best existing plants the dimensions to be given to the generator +relatively to those of the engine to be supplied, upon the assumption +that the engine is single-acting and runs at a normal speed of from 160 +to 230 revolutions per minute. The essential portion of the generator +which contributes to the production of a proper gas is that which +corresponds with the combustion zone. To this portion a cross-section is +given varying in size between one-half and one-quarter of the surface of +the engine-piston, sometimes between one-half and nine-tenths of this +surface, according to the nature and the size of the fuel that is used. +With small apparatus, however, ranging from 5 to 15 horse-power, the +size of the base cannot be reduced below a certain limit, since +otherwise the sinking of the fuel will be prevented. This danger always +exists in small generators and renders their operation rather uncertain, +such uncertainty being also due to the influence of the walls. It is to +be noted that most modern generators are rather too large than +otherwise. + +Many manufacturers of no wide experience have been led to make their +apparatus rather large so as to insure a more plentiful production of +gas. As a matter of fact, the fire in such apparatus is liable to be +extinguished when the combustion is not very active. If the principles +of the formation of gas in suction-generators be kept in mind, it is +evident that the gas developed is the richer the "hotter" the operation +of the apparatus. Such operation also permits the decomposition of the +hydrogen and carbon monoxide. + +The "hot" operation of a generator is accomplished best with active +combustion; and since this is a function of the rapidity with which the +air is fed, it obviously is advantageous to reduce the area of the +air-passage to a minimum as far as allowed by the amount of fuel to be +treated. As to the height of the fuel in use in the apparatus, this +varies as a rule between 4 and 5 times the diameter at the base. + +=Vaporizer.=--The size of the vaporizer varies materially according to +its type. No hard-and-fast rule can therefore be adopted for determining +its heating surface; but this surface should in all cases be sufficient +to vaporize under atmospheric pressure from .66 to .83 pounds of water +per pound of anthracite coal consumed in the generator. + +=Scrubber.=--For the scrubbers, the following dimensions may be deduced +from constructions now used by standard manufacturers. + +The volume of a scrubber is generally from six to eight times the +anthracite capacity of the generator. A height of from three to four +times the diameter is considered sufficient in most cases. It should be +understood that in this height is included the water-pan chamber located +below the partition or grate, and the upper chamber through which the +gas escapes. The height of these two chambers depends necessarily upon +the arrangement used for leading the gas to the lower portion of the +washer and for the distribution of wash-water at the top. + +=Assembling the Plant.=--The author has insisted strongly on the +necessity of having all the apparatus and pipe connections perfectly +tight. In order to ascertain if there is any leakage, the following +procedure may be adopted: + +When starting the fire by means of wood, straw, or other fuel producing +smoke, instead of allowing this smoke to escape through the flue during +the operation of the fan, it may be caused to escape through the cock +which generally admits the gas to the motor, the cock being opened for +this purpose. The damper in the outlet flue is closed. In this manner +the smoke will fill all the apparatus and connecting pipes under a +certain pressure and will escape through any cracks, the presence of +which will thus be revealed. + +Another test, which is made during the ordinary operation of the +generator, consists in passing a lighted candle along the joints; if +there is any leakage, this will be shown by a deviation of the flame +from a vertical position. + +=Fuel.=--We have discussed the subject of fuel in a preceding chapter +(Chapter XIII) and have indicated the conditions to be fulfilled by low +grade or anthracite coal best adapted for use in suction gas-generators. +It may here be added that the coal used in the generator should be as +dry as possible and in pieces of from 1/2 inch to 1 inch. Very small +pieces, and particularly coal dust, are injurious and should be removed +by preliminary screening as far as possible. Screened coal is thrown in +with an ordinary grate shovel. + +=How to Keep the Plant in Good Condition.=--In regard to the generator, +apart from the cleaning of the grate and of the ash-pit, which may be +done during operation, it is necessary to empty the apparatus entirely +once a week, if possible, in order to break off the clinkers adhering +to the retort. These clinkers destroy the refractory lining, form rough +projections interfering with the downward movement of the fuel, bring +about the formation of arches, and reduce the effective area of the +retort. At the time of this cleaning, tests are also made as to the +tightness of the doors of the combustion-chamber, of the charging-boxes, +etc. + +The vaporizer should be cleaned every week or every other week, +according to the more or less bituminous character of the fuel and the +greater or smaller content of lime in the water used. Lime deposits may +be eliminated, or the salts may be precipitated in the form of +non-adhering slimes, by introducing regularly a small amount of caustic +potash or soda into the feed-water. If the deposits or incrustations are +very tenacious, the use of a dilute solution of hydrochloric acid may be +resorted to. Tar which may adhere to the conduits, pipes or gas +passages, is best removed while the apparatus is still hot, or a solvent +may be employed, such as kerosene, turpentine, etc. The connections +between the vaporizer and the scrubber are particularly liable to become +obstructed by the accumulation of tar or dust carried along by the gas. + +It is advisable to examine the several parts of the plant once or twice +a week by opening the covers or the cleaning-plugs. + +The lower compartment of the washer keeps back the greater part of the +dust which has not been retained in collectors or boxes provided +especially for this purpose. The dust takes the form of slime, and, in +some arrangements of apparatus, tends to clog up the overflow pipe, +thus arresting the passage of gas and causing the engine to stop. This +portion of the washer should be thoroughly cleaned once or twice a +month. + +If very hard blast-furnace coke is used in the washer, it may be kept in +use for over a year without requiring removal. In order to free the +purifying materials from dust and lime sediments carried along by the +wash-water, it is well to let the wash-water flow as abundantly as +possible for about a half-hour at least once a month. At the time of +renewing the purifying material the precautions indicated in the section +dealing with these matters should be observed, and care should be taken +to have shelves or gratings on which the material is supported in layers +not too thick, so as to avoid any resistance to the passage of the gas. + +In a general way it is advisable to test the drain-cocks on the several +apparatus daily, and to keep them in perfect condition. If, when open, +one of these cocks does not discharge any gas, water, or steam, a wire +should be introduced into the bore to make sure it is not clogged up. + +=Care of the Apparatus.=--Each producer-gas plant will require special +instructions for running it, according to the system, the construction, +and the size of the plant. Such instructions are generally furnished by +the manufacturer. However, there are some general rules which are common +to the majority of suction gas-producers, and these will here be +enumerated. + +=Starting the Fire for the Gas Generator.=--This operation calls for +the presence of the engineer of the plant and an assistant. The proper +procedure is as follows: + +First: Open the doors of the furnace and of the ash-pit. Then open the +outlet flue and make sure that the grate of the generator is clear of +ashes and clinkers. It should also be seen to that the parts of the +charging-box work well and that the joints are tight. + +Second: Ascertain whether there is the proper amount of water in the +vaporizer, in the scrubber, etc., and that the feed works properly. + +Third: Through the door of the combustion-chamber introduce straw, wood +shavings, cotton waste, etc.; light them and fill the generator with dry +wood up to one-quarter or one-half of its height; then add a few +pailfuls of coal. + +Fourth: Close the doors of the ash-pit and of the combustion-chamber and +start the draft by means of the fan. As soon as the draft is started, it +must be kept up without interruption until the engine begins to run, +which may be ten or twenty minutes after lighting the fire. + +Fifth: After the draft has been continued for a few minutes, the coal +becomes sufficiently incandescent to start the production of gas, which +may be ascertained by trying to light the gas at the test-cock near the +generator. Then the opening in the outlet flue is half closed for the +purpose of producing pressure in the apparatus. + +Sixth: Open the outlet flue adjacent to the engine for the purpose of +purging the apparatus and the conduits of the air which they contain +until the gas may be lighted at the test-cock placed near the motor. + +Seventh: Adjust the normal outflow of wash-water for the scrubber. + +Eighth: As soon as the gas burns continuously at the test-cock with an +orange-colored flame the engine may be started. + +The gas at first burns with a blue flame; this color indicates that it +contains a certain amount of air. The opening of the test-cock should be +so regulated as to reduce the outlet pressure of the gas sufficiently to +prevent the flame from going out. During the production of the draft, as +well as during the ordinary running of the plant, the filling of the +apparatus with fuel should be done with care to prevent explosions of +gas due to the entrance of air. Particular care should be taken never to +open at the same time the lid of the charging-box and the device, be it +a cock, valve, or damper, which controls the connection of the +charging-box with the generator. All the operations which have been +mentioned above should be carried out as quickly as possible. + + + STARTING THE ENGINE + +The manner of starting the engine depends on the type of the engine and +on the starting device with which it is provided, as we have already +explained in connection with engines working with gas from city mains. + +It is, however, important for the production of a good explosive mixture +to regulate the amount of air supplied to the engine according to the +quality of the gas employed. It is advisable to continue the operation +of the fan until several explosions have taken place in the cylinder and +the engine has acquired a certain speed so as to be able to draw in the +normal amount of gas. + +Naturally the gas-outlet tube near the admission-cock should be closed +after starting the engine, as well as the opening in the outlet flue of +the generator. When the motor is running properly, the amount of water +fed to the vaporizer and overflowing to the ash-pit is properly +adjusted. The generator is then filled up to the level indicated by the +manufacturer. + +=Care of the Generator during Operation.=--As soon as the apparatus is +running under normal conditions, it presents the advantage of requiring +only very slight supervision and very little manual tending. The +supervision consists: + +First: In regulating and keeping up a proper feed of water to the +vaporizer. + +Second: In seeing to it that in apparatus provided with an overflow +leading to the ash-pit, the water should flow constantly but without +exceeding the proper amount. + +Third: In keeping down temperature in the scrubber by properly +regulating the feed of the wash-water. This apparatus may be slightly +warm at its lower part, but must be quite cold at the top. + +The manual tending to be done is limited to the regular filling up of +the generator with fuel and to the removal of ashes and clinkers. The +charging is effected at regular intervals, which, according to the +various types of anthracite-generators, vary from one to six hours. +Charging the apparatus at short intervals entails unnecessary labor, +while charging at too long intervals will often interfere with the +uniform production of the gas. + +It will be obvious that the amount of fuel introduced will be the +larger, the greater the intervals between two fillings. This fuel is +cold and contains between its particles a certain amount of air; +furthermore, the layer of coal which covers the incandescent zone has +become relatively thin. The excess of air impoverishes the gas, and the +fresh fuel lowers the temperature of the mass undergoing combustion, so +that again the gas in process of formation is weakened. Experience seems +to show that as a rule it is best to fill up the generator at intervals +of from two to three hours, according to the work done by the engine. It +should be noted that the level of the fuel in the generator should not +sink below the bottom of the feed-hopper. + +The author wishes again to emphasize that in order to prevent the +harmful entrance of air, the charging operations should be carried out +as quickly as possible; and for this reason the fuel should be +introduced not by means of the shovel, but by means of a pail, scuttle, +or other appropriate receptacle. + +Care should be taken to fill the charging box to its upper edge and to +adjust its cover accurately before operating the device which closes the +feed-hopper (valve, cock). + +The removal of the ashes and clinkers should be accomplished as +infrequently as possible, since opening the doors of the ash-pit and of +the combustion-chamber necessarily causes an inward suction of cold air +which is harmful. + +As a rule with generators employing anthracite coal, it is sufficient to +empty the ash-pit twice daily; this should be preferably done during +stoppages. However, the cleaning of the grate by means of a poker passed +between the grate-bars or over them in order to bring about the falling +of the ashes, should be attended to every two to four hours, according +to the type of the generator and the nature of the fuel. In order that +this cleaning may be done without opening the doors, the latter should +be provided with apertures having closing devices. + +This cleaning has for its chief object to allow the free passage of the +air for supporting combustion and to keep the incandescent zone in the +apparatus at the proper height. The accumulation of ashes and clinkers +at the bottom of the retort will shift this zone upward and impair the +quality of gas. + +=Stoppages and Cleaning.=--After closing the gas-inlet to the engine, +the damper in the gas-outlet flue of the generator should be opened and +the cocks controlling the feed of water to the scrubber and to the +vaporizer should be closed. + +If it is desired to keep up the fire of the generator during the +stoppage so as to be able to start again quickly, the ash-pit door +should be opened so as to produce a natural draft which will maintain +combustion. While the door is open, the clinkers which have accumulated +above the grate may be removed, as they are much more easily taken off +the grate when they are hot. + +At least once a week the fire in the generator should be put out and the +generator completely cleaned--that is, when ordinary fuel is employed. +For this purpose, as soon as the apparatus is stopped, a portion +of the incandescent fuel is withdrawn through the doors of the +combustion-chamber, and the retort is allowed to cool before it is +emptied entirely. Too sudden a cooling of the retort may injure its +refractory lining. In order to prevent explosions caused by the entrance +of air, the feed-hopper should remain hermetically closed during the +removal of the incandescent fuel through the doors of the +combustion-chamber. + +If the apparatus is placed in a room poorly ventilated, the cleaning +should be attended to by two men, so that one may assist the other in +case he is overcome by the gas. In all cases there should be a strict +prohibition against the use of any light having an exposed flame liable +to set on fire the explosive mixtures which may be formed. + +When the generator, after cooling, is completely open, the charging-box +is taken apart, and, if necessary, the feed-hopper also; the grates are +taken out, if necessary; and, by means of a poker inserted from above, +the clinkers and slag adhering to the retort are broken off. + +In the foregoing paragraphs the author has indicated how the several +apparatus, such as the vaporizer, the washer, the conduits, etc., should +be attended to and maintained in good working order. + + + + + CHAPTER XIV + + OIL AND VOLATILE HYDROCARBON ENGINES + + +Although this book is devoted primarily to a discussion of street-gas +and producer-gas engines employed in various industries, a few words on +oil and volatile hydrocarbon engines may not be out of place. + +Oil-engines are those which use ordinary petroleum as a fuel or +illuminating oil of yellowish color, having a specific gravity varying +from 0.800 to 0.820 at a temperature of 15 degrees C. (59 degrees F.), +and boiling between 140 and 145 degrees C. (284 to 297 degrees F.). +Volatile hydrocarbon engines are those which employ light oils obtained +by distilling petroleum. These oils are colorless, have a specific +gravity that varies from 0.680 to 0.720, and boil between 80 degrees and +115 degrees C. (176 to 257 degrees F.). Among these "essences," as they +are called in Europe, may be mentioned benzine and alcohol. + +In general appearance, and the way in which they are controlled, +oil-engines differ but little from gas-engines. Their usual speed, +however, is 20 to 30 per cent. greater than that of gas-engines. Except +in some engines of the Diesel and Banki types, the compression does not +exceed 43 to 71 pounds per square inch. In volatile hydrocarbon engines, +on the other hand, the speed is very high, often running from 500 to +2,000 revolutions per minute, while the speed of gas or oil engines +rarely exceeds 250 or 300 revolutions per minute. + +=Oil-Engines.=--Oil-engines are employed chiefly in Russia and in +America. Because of the high price of oil in other countries they are to +be found only in small installations in country regions and are used +mainly for driving locomobiles and launches. The improvements which have +been made of late years in the construction of gas-engines supplied by +suction gas-producers for small as well as for large powers, have +hindered the general introduction of oil-engines. + +The characteristic feature in the design of many of the oil-engines of +the four-cycle type now in use (to which type we shall confine this +discussion) is to be found in the controlling mechanism employed. The +underlying principle of this mechanism lies not in acting upon the +admission-valve, but in causing the governor to operate the +exhaust-valve in such a manner that it is held open whenever the engine +tends to exceed its normal speed. Some engines, however, are built on +the principle of the gas-engine, with an admission-valve so controlled +by the governor that it is open during normal operation and closed +whenever the speed becomes excessive. + +The necessity of producing a mixture of air and oil capable of being +ignited in the engine-cylinder has led to the invention of various +contrivances, which cannot be used if illuminating-gas or producer-gas +be employed. These contrivances are the atomizer, the carbureter, the +oil-pump, the air-pump, the oil-tank, and the oil-lamp. In some +oil-engines all of the elements may be found, but for the purpose of +simplifying the construction and of avoiding unnecessary complications, +manufacturers devised arrangements which rendered it possible to discard +some of them, particularly those of delicate construction and operation. +It is not the intention of the author to enter into a detailed +description of these various devices, since the limitations of this book +would be considerably surpassed. The reader is referred to books on the +oil-engine, published in the United States, England, and France.[B] + +Most of the observations which have been made on the construction and +installation of gas-engines, as well as the precautions which have been +advised in the conduct of an engine, apply with equal force to +oil-engines. It will therefore be unnecessary to recur to this phase of +the subject so far as oil-engines are concerned. One point only should +be insisted upon--the necessity of very frequently cleaning the valves +and moving parts of the engine. + +Illuminating-oil when burnt produces sooty deposits, particularly if +combustion be incomplete, which deposits foul the various parts and +cause premature ignitions and faulty operation. + +The use of oil in atomizers, carbureters, and lamps is accompanied with +the employment of pipes and openings so small in cross-section that the +slightest negligence is attended with the formation of partial +obstructions that inevitably affect the operation of the engine. + +=Volatile Hydrocarbon Engines.=--Only those engines will here be treated +which have become of importance in the development of the automobile. + +Some designers have attempted to employ the volatile hydrocarbon engine +for industrial and agricultural purposes, and have devised +electro-generator groups, hydraulic groups, and so-called "industrial +combinations" in which belt and pulley transmission is employed. These +applications in particular will here be rapidly reviewed. + +The high speed at which engines of this class are driven renders it +possible to operate a centrifugal pump directly and to mount both the +engine and machine which it actuates on the same base. The hydrocarbon +engine has the merit of being very light and of taking up but little +room. Its cost is considerably less than that of an oil or producer-gas +engine of corresponding power. On the other hand, its maintenance is +much more expensive, and the hydrocarbons upon which it depends for fuel +anything but cheap. Furthermore, the engines wear away rapidly, on +account of their high speed. For this reason it is advisable to base +calculations on a life of three to four years, while oil and gas engines +may generally be considered to be still of service at the end of +thirteen years. On the following page a comparison of costs for +installation and maintenance is drawn between the oil and hydrocarbon +engine on the basis of ten horse-power. + +=Comparative Costs.=--A 10 horse-power oil-engine, in the matter of +first cost of installation, is about 35 per cent. more expensive than a +volatile hydrocarbon engine of equal power. On the other hand, the +operating expenses of the oil-engine are less by 25 per cent. than they +are for the volatile hydrocarbon engine. + +The engines which are here discussed usually have their cylinders +vertically arranged, as in steam-engines of the overhead cylinder type. +The crank-shaft and the connecting-rods are enclosed in a hermetically +sealed box filled with oil, so that the movement of the parts themselves +ensures the liberal lubrication of the piston. The suction-valve is +generally free, although latterly designers have shown a tendency to +connect it with the cam-shaft, with the result that it has become +possible to reduce the speed appreciably without stopping the engine. +The carbureter is operated by the suction of the engine. If the fuel +employed is alcohol, it must be heated. + +=Tests of High-speed Engines.=--High-speed engines present various +difficulties which must be contended with in controlling their +operation. Their high speed renders it impossible to take indicator +records as in the case of most industrial engines. Indicator cards, +moreover, at best give but very crude data, which relate to each +explosion cycle only, and which are therefore inadequate in determining +the exact conditions of an engine's operation. Oil, benzine, and other +so-called carbureted-air engines are particularly difficult to control +because of many phenomena which cannot be recorded. In order to test the +operation of high-speed engines, two different types of instruments are +at present employed: the manograph and the continuous explosion +recorder. + +=The Manograph.=--The manograph, which is the invention of Hospitalier, +is an optical instrument in which a series of closed diagrams are +superimposed upon a polished mirror similar in form to Watt diagrams. +Because the images persist in affecting the retina of the eye an +absolutely continuous, but temporary, gleam is seen. Still, it is +possible to obtain a photograph or a tracing of these diagrams. + +=The Continuous Explosion Recorder for High-speed Engines.=--The author +has devised an explosion and pressure recorder, which is mounted upon +the explosion chamber to be tested and which communicates with the +chamber through the medium of a cock _r_ (Fig. 136). The instrument is +somewhat similar in form to the ordinary indicator. Its record, however, +is made on a paper tape which is continuously unwound. The cylinder _c_ +is provided with a piston _p_, about the stem of which a spring _s_ is +coiled. A clock train contained in the chamber _b_ unwinds the strip of +paper from the roll _p'_ and draws it over the drum _p''_, where the +pencil _t_ leaves its mark. The tape is then rewound on the spindle +_p'''_. A small stylus or pencil _f_ traces "the atmospheric line" on +the paper as it passes over the drum _p''_. In order to obviate the +binding of the piston _p_ when subjected to the high temperature of the +explosions, the cylinder _c_ is provided with a casing _e_ in which +water is circulated by means of a small rubber tube which fits over the +nipple _e'_. This recorder analyzes with absolute precision the work of +all engines, whatever may be their speed. It gives a continuous graphic +record from which the number of explosions, together with the initial +pressure of each, can be determined, and the order of their succession. +Consequently the regularity or irregularity of the variations can be +observed and traced to the secondary influences producing them, such as +the section of the inlet and outlet valves and the sensitiveness of the +governor. It renders it possible to estimate the resistance to suction +and the back pressure due to expelling the burnt gases, the chief causes +of loss in efficiency in high-speed engines. Furthermore, the influence +of compression is markedly shown from the diagram obtained. + +[Illustration: FIG. 136.--R. Mathot's continuous explosion recorder.] + +[Illustration: FIG. 137.--12 H.P. Oil-engine.] + +[Illustration: FIG. 138.--6 H.P. Volatile Hydrocarbon Engine.] + +[Illustration: FIG. 139.--Effect of size of section and exhaust ports.] + +The recorder is mounted on the engine; its piston is driven back by each +of the explosions to a height corresponding with their force; and the +stylus or pencil controlled by the lever _t_ records them side by side +on the moving strip of paper. The speed with which this strip is unwound +conforms with the number of revolutions of the engine to be tested, so +that the records of the explosions are placed side by side clearly and +legibly. Their succession indicates not only the number of explosions +and of revolutions which occur in a given time, but also their +regularity, the number of misfires. The atmospheric pressure of the +explosions is measured by a scale connected with the recorder-spring. By +employing a very weak spring which flexes at the bottom simply by the +effect of the compression in the engine-cylinder, it is possible to +ascertain the amount of the resistance to suction and to the exhaust. It +is simply sufficient to compare the explosion record with the +atmospheric line, traced by the stylus _f_. By means of this apparatus, +and of the records which it furnishes, it is possible analytically to +regulate the work of an engine, to ascertain the proportion of air, gas, +or hydrocarbon, which produces the most powerful explosion, to regulate +the compression, the speed, the time of ignition, the temperature, and +the like (Figs. 137, 138 and 139). + +In order to explain the manner of using this recorder several specimen +diagrams are here given. + +I. _Determination of the Amount of Compression._--A spring of average +power is employed, the total flexion of which corresponds almost with +the maximum compression so as to obtain a curve of considerable +amplitude. The engine is first revolved without producing explosions, +driving it from the dynamo usually employed in shops, at the different +speeds to be studied. The compression of the mixture varies in inverse +ratio to the number of revolutions of the shaft, owing to the +resistances which are set up in the pipes and the valves and which +increase with the speed. The accompanying cut (Fig. 140) shows two +distinct records taken in two different cases, namely: + +A.--Speed of engine, 950 revolutions per minute; amount of compression, +68.9 pounds per square inch. + +B.--Speed of engine, 1,500 revolutions per minute; amount of +compression, 61 pounds per square inch, or 11.5 per cent. less. + +[Illustration: FIG. 140.] + +II. _Determination of the Resistance to Suction and Exhaust._--Influence +of the tension of the spring of the suction valve and of the section of +the pipe. Effect of the section of the exhaust-valve and of the length +and shape of the exhaust-pipe: + +A very light spring is utilized, the travel of which is limited by a +stop so as to obtain on a comparatively large scale the depressions and +resistance respectively represented by the position of the corresponding +curve, above or below the atmospheric line (Fig. 141). + +[Illustration: FIG. 141.] + +C.--Tension of the suction-valve: 2.9 pounds. Resistance to suction: 1/7 +of an atmosphere (2.7 pounds). + +D.--Tension of the suction-valve: 2.17 pounds. Resistance to suction: +2/7 of an atmosphere (5.4 pounds). + +E.--A chest is used for the exhaust. Resistance to exhaust: 2/7 of an +atmosphere (5.4 pounds). + +F.--The exhausted gases are discharged into the air, the pipe and the +chest being discarded. Resistance to the exhaust is zero (Fig. 142). + +[Illustration: FIG. 142.] + +The depression graphically recorded is partly due to the inertia of the +spring of the explosion-recorder, which spring expands suddenly when the +exhaust is opened. + +III. _Comparison of the Average Force of the Explosions by Means of +Ordinates._--A powerful spring is employed. The paper band or tape of the +recorder is moved with a small velocity of translation so as to +approximate as closely as possible the corresponding ordinates +representing the explosions (Fig. 143). + +[Illustration: FIG. 143.] + +G.--Pure alcohol. Explosive force, 369.72 to 426.6 pounds per square +inch. + +H.--Carbureted alcohol. Explosive force, 397.6 to 510.8 pounds per +square inch. + +I.--Volatile hydrocarbon. Explosive force, 483.48 to 531.92 pounds per +square inch. + +IV. _Analysis of a Cycle by Means of Open Diagrams Representing the Four +Periods._--A powerful spring is employed, and the paper is moved with +its maximum speed of translation. The four phases of the cycle are +easily distinguished as they succeed one another graphically from right +to left in other words, in a direction opposite to that in which the +paper is unwound. A diagram is made which reproduces exactly the values +of the corresponding pressures at different points in the travel of the +piston (Fig. 144). The periods of the cycle are reproduced as faithfully +as if the ordinary indicator which gives a closed curved diagram had +been employed. There is no difficulty in reading the record, since the +paper is not in any way connected with the engine-piston. Some attempts +have been made to secure open diagrams in which the motion of +translation given to the paper is controlled by the engine itself; but +these apparatus as well as the ordinary indicators cannot be used when +the speed of the engine exceeds 400 to 500 revolutions per minute. + +[Illustration: FIG. 144.] + +J.--Speed, 1,200 revolutions; carbureted alcohol; average force of the +explosions, 426.6 pounds per square inch. Average compression, 92.43 +pounds per square inch. Pressure at the end of the expansion, 21.33 +pounds per square inch. + +V. _Analysis of the Inertia of the Recorder. Selection of the Spring to +be Employed._--Given the rapidity with which the explosions succeed one +another in automobile engines, it is readily understood that the inertia +of the moving parts of the recorder will be graphically reproduced (Fig. +144). The effect of this inertia is a function of the weight of the +moving parts and of the extent of their travel. + +The moving masses are represented by the piston and its rod, the spring +and the levers of the parallelogram stylus. The effects due to inertia +have been considerably lessened by reducing the weight of the various +parts to a minimum. A hollowed piston, a hollowed rod and short and +light levers have been adopted. The traditional pencil has been +displaced by a silver point which traces its mark upon a metallically +coated paper. For the heavy springs with their long travel, light but +powerful springs with small amplitudes have been substituted. Since the +perfect lubrication of the recorder-cylinder is of great importance, a +simple oiling device certain in its action has been adopted. The recess +of the piston forms a cup that can be filled with oil whenever the +spring is changed. + +At each explosion the violent return of the piston splashes oil against +the cylinder walls and thus insures perfect lubrication. It should be +observed that if the directions given are not followed, particularly in +the choice of a spring suitable for each experiment, inertia effects +will be produced. These can easily be detected on the record and cannot +be confused with the curves which interpret the phenomena occurring in +the cylinder of the engine. At a height equal to the end of the piston's +stroke, the cylinder of the recorder is provided with a water-jacket +which keeps the temperature down to a proper point and prevents the +binding of the piston. + +The explosion-chamber of automobile engines being rather small in +volume, should not be sensibly increased in order that the record +obtained may conform as nearly as possible with actual working +conditions on the road. In order to attain this end the cylinder of the +recorder is so disposed that the piston travels to the height of the +connecting-cock. As a result of this arrangement the field of action of +the gases is reduced to a minimum. Since these gases have no winding +path to follow, they are subjected neither to loss of quantity nor to +cold. + + + FOOTNOTES: + +[B] Hiscox, Gas and Oil Engines, Norman W. Henley Pub. Co., New York. +Parsell and Weed, Gas and Oil Engines, 1900, Norman W. Henley Pub. Co., +New York. Goldingham, 1900, Spon & Chamberlain, London. Dugald Clerk, +1897, Longmans, London. Grover, 1902, Heywood, Manchester. Aime. Witz, +1904, Barnard, Paris. H. Gueldner, 1903, Springer, Berlin. + + + + + CHAPTER XV + + THE SELECTION OF AN ENGINE + + +The conditions which must be fulfilled both by engines and gas-producers +in order that they may industrially operate with regularity and economy +have been dwelt upon at some length. Unfortunately it often happens that +engines are not installed as they should be, with the result that they +run badly and that the reputation of gas-engines suffers unjustly. The +use of suction gas-producers in particular caused considerable trouble +at first owing to inexperience, so that even now many hesitate to adopt +them despite their great economical advantages. The reason assigned for +this hesitation is the supposed danger attending their operation. + +The factory proprietor who intends to install a gas-engine in his plant +is not usually able to appreciate the intrinsic value of one engine when +compared with another, or to determine whether the plans for an +installation conform with the best practice. The innumerable types of +engines offered to him by manufacturers and their agents, each of whom +claims to have a better engine than his rivals, plunges the purchaser +into hesitation and doubt. Not knowing which engine to select, he +usually buys the cheapest. Very often he learns, as time goes by, that +his installation is far from being perfect. Finally he begins to +believe that he ought to consult an expert. The author's personal +experience has convinced him that eight times out of ten the factory +owner who has picked out an engine for himself has not obtained an +installation which meets the requirements which the manufacturers of +gas-engines should fulfil. Many of these requirements could be complied +with were it not for the fact that the manufacturer has dropped certain +details which appeared superfluous, but which were in reality very +important in obtaining perfect operation. The author therefore suggests +that the services of a competent expert be retained by those who intend +to install a gas-engine in their plants. + +=The Duty of a Consulting Engineer.=--An expert fills the same office as +an architect, and impartially selects the engine best suited to his +client's peculiar needs. His examination of the engines offered to him +will proceed somewhat according to the following programme: + +1. He will first study the installation from the mechanical point of +view, and also the local conditions under which that installation is to +operate, in order that he may not order an engine too large or too +small, or a type incompatible with the foundations at his disposal, or +unable to fulfil all the requirements of his client. + +2. He will examine the precautions which have been taken to avoid or +reduce to a minimum certain inconveniences which attend the operation of +explosion-engines. + +3. He will draw up specifications, with the terms of which gas-engine +makers must comply, so that he can compare on the basis of these +specifications the merits of the engines submitted to him. + +4. He will prepare an estimate of cost and also a contract which is not +couched in terms altogether in the gas-engine maker's favor, and which +gives the purchaser important warranties. + +5. He will supervise the technical installation of the engine or plant. + +6. He will make tests after the engine is installed and see to it that +the maker has fulfilled his warranties. + +=Specifications.=--Since engines and gas-producers are constructed for +commercial ends, it naturally follows that their manufacturers seek to +make the utmost possible profit in selling their installations. Prices +charged will necessarily vary with the quality of material employed, the +care taken in constructing the engine and generator, the number of +apparatus of the same type which are manufactured, the arrangement of +the parts and that of the installations. Since there is considerable +rivalry among gas-engine builders, selling prices are often cut down so +far that little or no profit is left. It is very difficult--indeed +impossible--to convince a purchaser that it is to his interest to pay a +fair price in order to obtain a good installation, especially when other +manufacturers are offering the same installation at a less price with +the same warranties. As a result of this state of affairs, engine +builders, in order that they may not lose an order, are willing, to +reduce their prices, hoping to make up in the quality of the +workmanship and the material what they would otherwise lose. Often they +will deliver an engine too small in size but operating at a higher speed +than that ordered; or they will select an old type, or carry out certain +details with no great care. + +This, to be sure, is not always the case; for there are a few builders +of engines who place their reputation above everything else and who +would rather lose an order than execute it badly. Others, unfortunately, +prefer to have the order at all costs. + +By retaining a consulting engineer, all these difficulties are overcome. +In the first place, the engineer draws up a scale of prices and +specifications which must be complied with in their entirety as well as +in all details. Rival engine builders are thus compelled to make their +estimates according to the same standard, so that one engine can readily +be compared with another with the utmost fairness. In these +specifications, penalties will be provided for by the engineer which +will be levied if the warranties of the maker are not fulfilled. +Otherwise the warranties are worth nothing. + +The first consequence of engaging a consulting engineer is to render the +matter of cost a secondary one. A factory owner who employs a consulting +engineer and pays him for his services, is impelled chiefly by the +desire to obtain a good installation which will perform what he expects +of it. For that reason necessary sacrifices will be made to comply with +the client's wishes. + +If the purchaser considers the question of cost most important to him, +he need not engage an expert to supervise the installation of his +engines. He has simply to pick out the cheapest engine. Unfortunately, +however, the money which he will save by such a procedure will be more +than compensated for by the trouble which he will later experience when +his motor stops or when it breaks down, because it has been cheaply +built in the first place. + +The advice of a consulting engineer is therefore of importance to the +purchaser, because an engine will be installed which will in every way +meet his requirements. The gas-engine builder will also prefer to deal +with an engineer, because the engineer can appreciate at their true +worth good material and good workmanship and place a fair valuation upon +them. The specifications of a gas-engine and gas-producer expert are +accepted by most engine builders, because an expert will not introduce +conditions which cannot be fulfilled. Some manufacturers refuse to +consider the conditions imposed by specifications seriously, or else +they fix different prices and make tenders on the basis of these with or +without specifications. In either case the purchaser may be sure that he +is not receiving what he has a right to exact. + +=Testing the Plant.=--When the engine has been selected the consulting +engineer supervises its installation, and, after this is completed, +carries out tests in order to determine whether or not the guaranteed +power and consumption are attained. The methods employed in testing a +gas-engine are both complex and delicate. The quality of the gas, the +proportions of the elements forming the mixture, the time and the +method of ignition, the temperature of the cylinder-walls, the +temperature and the pressure of the gas drawn into the cylinder, all +these are factors which have a decided bearing upon the results of a +test. If these factors be not carefully considered the conclusions to be +drawn from the test may be absolutely wrong. + +Indicators of any type should not be indiscriminately employed; only +those specially designed for gas-engine purposes should be used. +Indicator cards are in themselves inadequate, and should be supplemented +by the records of explosion-recorders. + +The calorific value of the gas should be measured either by the Witz +apparatus or by means of any other calorimeter. + +In interpreting the diagrams and records some difficulty will be +encountered. Sometimes it happens that a particular form of curve is +attributed to a cause entirely different from the real one. It happens +not infrequently that engineers, whose experience is confined to engines +of one make and who have not had the opportunity to make sufficient +comparisons, draw such erroneous conclusions from cards. + +To recapitulate what has already been said, the testing of gas-engines +requires considerable experience and cannot be lightly undertaken. +Special instruments of precision are necessary. The author has very +often been called upon to contradict the results obtained by experts +whose tests have consisted simply in ascertaining the engine power +either by means of a Prony brake, or by means of a brake-strap on the +fly-wheel. The brake gives but crude results at best; it is a means of +control, and not an instrument of scientific investigation. + +Something more than the mere power produced by an engine should be +ascertained. The tests made should throw some light upon the reasons why +that power cannot be exceeded, and show that the necessary changes can +be made to cause the engine to operate more economically and to yield +energy of an amount which its owner has a right to expect. The indicator +and the recorder are testing instruments which clearly indicate +discrepancies in operation and the means by which they may be corrected. +The tests made should determine whether the power developed is not +obtained largely by means of controlling devices which cause premature +wearing away of the engine parts. + +It is not the intention of the author to describe indicators of the +well-known Watt type. It is simply his purpose to call attention to the +explosion-recorder which he has devised to supplement the data obtained +by means of the indicator. + +[Illustration: FIG. 145.--Mathot explosion-recorder.] + +=Explosion-Recorder for Industrial Engines.=--The explosion-recorder +illustrated in Fig. 145 can be adapted to any ordinary indicator. It is +composed of a supporting bracket _B_ upon which a drum _T_ is mounted. +This drum is rotated by a clock-train, the speed of which is controlled +by means of a special compensating governor. The entire system is +pivotally mounted upon the supporting screw _O_, so that the drum _T_, +about which a band of paper is wound, may be swung against a stylus +_C_, which records upon the paper the number and power of the +explosions. These explosions are measured according to scale by a spring +connected with an indicator. The records obtained disclose for any given +cycle the amount of compression as well as the force of the explosion, +and render it possible to study the phenomena of expansion, exhaust, and +suction. They are, however, inadequate in showing exactly how an engine +runs in general. Indeed, in most gas-engines, as well as oil and +volatile hydrocarbon engines, each explosion differs from that which +follows in character and in power; and it is absolutely essential to +provide some means of avoiding these variations. The explosion-recorder +gives a graphic record from which the number of explosions can be read, +and also the initial pressure of each explosion, the number of +corresponding revolutions, the order in which the explosions succeed one +another, and consequently the regularity of certain phenomena caused by +secondary influences, such as the section of the distributing members, +the sensitiveness of the governor, and the like. + +The explosion-records can be taken simultaneously with ordinary +diagrams. In order to attain this end, the recorder is allowed to swing +around the pivot _O_, so that the drum carrying the paper band is +brought into engagement, or swung out of engagement with the stylus, as +it is influenced by each explosion, thereby leaving its record on +the paper. The ordinary diagram may be traced on the drum of the +indicator, as it continues to operate in its usual way. Thus the +explosion-recorder renders it possible to control the operation of +engines, to obtain some idea of the cause of defects and to attribute +them to the proper force. Improvements can then be made which will +ensure a greater efficiency. A number of records herewith reproduced +illustrate the defects in the controlling apparatus and in the +construction of certain engines, and also the result of improvements +which have been made on the basis of the records obtained. The smaller +lines indicate the compression, which is usually constant in engines in +which the "hit-and-miss" system of governing is employed, while the +larger lines indicate the explosions. These records are only part of the +complete data normally drawn on the paper in the period of 120 seconds +corresponding with an entire revolution of the recorder-drum. + +[Illustration: FIG. 146.--Record with automatic starter.] + +[Illustration: FIG. 147.--Gas-engine running at one-half load.] + +[Illustration: FIG. 148.--Record made after correcting faults.] + +[Illustration: FIG. 149.--Record made after correcting faults.] + +The first record was taken while starting up an engine provided with an +automatic starting device and supplied with explosive mixture without +previous compression (Fig. 146). The gradual lessening of the distances +of the ordinates or lines representing the explosions shows that the +speed of the motor was slowly increasing, and also indicates the time +which elapsed before the engine was running smoothly. The records that +follow (Figs. 147, 148 and 149) show the results which can be obtained +with the recorder by correcting the errors due to faults in installing +the engine and its accessories. The fifth record is particularly +interesting because it shows the influence of the ignition-tube on the +power of the deflagration of the explosive mixture (Fig. 150). This +record was obtained with an engine provided with two contiguous tubes. +The communication of each of these tubes with the explosion-chamber +could be cut off at will at any moment. The last record (Fig. 151) was +obtained at a time when the effective load of the engine was changed at +two different intervals. This record shows how regularly the engine was +running and how constant were the initial pressures. These pressures, +however, which is the case in most engines, manifestly diminish when the +explosions succeed one another without idle strokes of the piston. This +shows, also, the influence of "scavenging" the products of combustion +and the effect it has on the efficiency of explosion-engines. + +=Analysis of the Gases.=--It has already been stated that one of the +tests which should be made consists in measuring the calorific value of +the gas. Just what the calorific value of the gas may be it is necessary +to know in order to obtain some idea of the thermal efficiency of the +installation. If a suction gas-producer be employed (an apparatus in +which the nature of the gas generated changes at each instant), +calorimetrical analyses are indispensable in appreciating the conditions +under which a generator operates. + +These analyses are made by means of calorimeters which give the +calorific value either at a constant pressure or at a constant volume. + +Constant-volume instruments give a somewhat weaker record than +constant-pressure instruments; but according to Professor Aime Witz, the +inventor of an excellent calorimeter, the constant-volume type is almost +indispensable in gaging the efficiency of explosion-engines. + +[Illustration: FIG. 150.] + +[Illustration: FIG. 150_b_.] + +[Illustration: FIG. 151.--Record made when effective load was changed at +two different intervals.] + +[Illustration: FIG. 152.--The Witz calorimeter.] + +=The Witz Calorimeter.=--The accompanying diagram (Fig. 152) illustrates +Professor Witz's instrument. Its elements are a steel cylinder having an +interior diameter of 2.36 inches, about a thickness of 0.078 inch and a +height of about 3.54 inches, so that its capacity is about 15.1 cubic +inches, and two covers screwed on the cylinder to seal it hermetically, +oiled paper being used as a washer. The upper cover carries a +spark-exciter; the lower cover is provided with a valve which discharges +into a cylindrical member 1.06 inches in diameter. This second cover is +downwardly inclined at its circumference toward the center to insure +complete drainage of the mercury used for charging the calorimeter. All +surfaces are nickel plated. The proportions of nickel and of steel are +fixed by the manufacturer so as to render it possible to calculate the +displacement of the apparatus in water. The calorimeter having been +completely filled with mercury is inverted in this liquid in the manner +of a test tube. The explosive mixture is then introduced, being fed +from a bell in which it has previously been prepared. A rubber tube +connects the bell with the instrument. The gas is forced from the bell +to the calorimeter by the pressure in the bell. The conical form of the +bottom causes the calorimeter to be emptied rapidly and to be refilled +completely with explosive gas at a pressure slightly above that of the +atmosphere. Equilibrium is re-established by manipulating the valve, +during a very short interval, so as to permit the excess gas to escape. +During this operation the calorimeter must be maintained in the vertical +position shown in the diagram. The atmospheric pressure is read off to +one-tenth of a millimeter (0.003936 inches) on a barometer. The +temperature of the gas may be taken to be that of the mercury-vessel. + +The explosive mixture is prepared in the water reservoir, the glass bulb +shown in the accompanying illustration being employed. This bulb is +closed at its upper end by means of a cock and is tapered at its lower +end. The gas or air enters at the top by means of a rubber tube and +gradually displaces the water through the lower end. The bulbs have a +volume varying from 200 to 500 cubic centimeters (12 to 30 cubic +inches), and the error resulting from each filling of a bulb is +certainly less than 15 cubic millimeters (0.0009 cubic inches). The +contents are emptied into a bell by lowering the bulb into the water and +opening the cock. If seven bulbfuls of air be mixed with one bulbful of +gas, an explosive mixture of 1 to 7 is produced, this being the +proportion commonly employed for street-gas. For producer-gases the +preferred proportion is 1 to 1, oxygen being often added to the air in +order to insure complete combustion. + +The calorimeter, after having been filled, is placed in a vessel +containing a liter (1.7598 pints) of water so that it is completely +immersed. A spark is then allowed to pass. The explosion is not +accompanied by any noise; the temperature rises a fixed number of +degrees, so that the quantity of heat liberated can easily be computed. +Each division of the thermometer is equal to 0.01502 C. The scale +reading is minute, each interval being divided by ten, so that readings +to the 1,500th part of a degree can be taken. + +It should be observed that the mixture generated in the reservoir is +saturated with water vapor at the temperature of the reservoir. +Consequently, the vapor generated by the explosion must condense in the +calorimeter if the final temperature of the calorimeter is the same as +that of the water reservoir. If, on the other hand, the temperature be +slightly different, a correction must be made; but the error is +negligible for differences in temperature of from 2 to 3 degrees C. (3.6 +to 5.4 degrees F.). This, however, is never likely to occur if the +operation is conducted under favorable conditions. + +This apparatus is exceedingly simple and practical. It does not require +the manipulation of a pump. The pressure of the mixture is read off on +the barometer; the calorimeter is entirely immersed in the water of the +outer vessel, so that all corrections of doubtful accuracy are obviated. +The method requires but a very slight correction for temperature. Air, +alone or mingled with oxygen, or a mixture of air and oxygen, can be +easily tested with. + +=Maintenance of Plants.=--If it should be necessary to retain a +consulting engineer to install an engine capable of filling all +requirements, it is also necessary to select a careful attendant in +order that the engine may be kept in good condition. It is a rather +widespread belief that a gas-engine can be operated without any care or +inspection. This belief is all the more prevalent because of the +employment of street-gas engines, which, by reason of their simplicity +of construction and regularity of fuel supply, often run for several +hours, and even for an entire day, without any attention whatever. But +this negligence, particularly in the case of engines driven from +producers, is likely to produce disastrous results. Although engines of +this type do not require constant inspection during operation, still +they require some attention in order that the speed may be kept at a +fixed number of revolutions. Moreover, the care of the engine, the +cleaning of the valves and of the various parts which are likely to +become dirty, and the examination and cleaning of pipes, should be +accomplished with great care and at regular intervals. This task should +be entrusted only to a man of intelligence. A common workman who knows +nothing of the care with which the parts of an engine should be handled +is likely to do more harm than good. + +The factory owner who follows the instructions which have been given in +this book will avoid most of the stoppages and the trouble incurred in +engine and generator installations, and may count upon a steadiness of +operation comparable with that of a steam-engine. + + + TEST OF A "STOCKPORT" GAS-ENGINE WITH DOWSON PRESSURE GAS PLANT + + Made by R. Mathot at the Works of the "Union Electrique" C^{ie}, + Brussels, June 27, 1901 + + Piston Diameter: 15-1/2". Piston stroke, 22". + Normal number of revolutions, 210. + + 1. Calorific value of the coal 12750 B.T.U. + 2. Nature and origin of fuel: Anthracite coal + of Charleroi (Belgium). + 3. Cost of fuel per ton at the mine $5.50 + 4. Cost of fuel per ton at the plant $6.39 + 5. Fuel consumption per hour in the generator 46.3 lbs. + 6. Fuel consumption per hour in the boiler 7 lbs. + 7. Proportion of ash in the coal 6 per cent. + 8. Weight of steam at 66 lbs. generated per hour 42.7 lbs. + 9. Average brake horse-power 53 B.H.P. + 10. Fuel consumption for gas per B.H.P. per + hour 0.875 lbs. + 11. Fuel consumption for steam per B.H.P. per hour 0.133 lbs. + 12. Total fuel consumption 1.008 lbs. + 13. Steam consumption at 66 lbs. pressure 0.81 lbs. + 14. Gas pressure at the engine 1-3/8 inches + 15. Weight of water per B.H.P. per hour for + cooling the cylinder entering at 68 deg. F. + and leaving at 105 deg. F. 51.5 lbs. + 16. Corresponding heat absorbed in cooling 1970 B.T.U. + 17. Average initial explosive pressure on piston 324 lbs. + 18. Average pressure on piston per square inch 72 lbs. + 19. Average indicated horse-power with 85 per + cent. misses 92.5 I.H.P. + 20. Corresponding mechanical efficiency 84 per cent. + 21. Corresponding electric load 31.950 K.W. + 22. Cost of B.H.P. per hour in anthracite $0.0029 + 23. Cost of kilowatt per hour in anthracite $0.0048 + 24. Electric power generated per B.H.P. 602.8 W. + 25. Thermal efficiency at 53 B.H.P. with 85 + per cent. explosions 18.5 per cent. + + + TEST OF A 20 H.P. WINTERTHUR ENGINE + + With Winterthur Suction-Producer made by R. Mathot at Winterthur, + June 4 and 5, 1902 + + DATA OF TESTS WITH ILLUMINATING GAS AND WITH FUEL GAS + +Dimensions of Winterthur Engine--Piston diameter: 10-3/8". Stroke: +16-7/8". Compression: 177 pounds per square inch. Regulation: hit and +miss. Ignition: electro-magnetic. Fly-wheel: normal, with external +bearing. Lubrication of piston: with oil-pump. Of main bearings, with +rings (as in dynamos). + + FULL LOAD WITH STREET-GAS + + 1. Number of revolutions per minute 200 + 2. Corresponding number of explosions 96 per cent. + 3. Net load on brake 120 lbs. + 4. Corresponding effective power 22 B.H.P. + + 5. Mean initial explosive pressure on piston + per square inch 455 lbs. + 6. Average pressure on piston per square inch 78 lbs. + 7. Gas consumption per B.H.P. at 24 deg. C. and + 721 mm. mean pressure 15.5 cubic feet + 8. Gas consumption per B.H.P. reduced to 0 deg. C. + and 760 mm. mean pressure 13.5 cubic feet + + HALF LOAD WITH STREET-GAS + + 9. Number of revolutions per minute 204 + 10. Corresponding number of explosions 60 per cent. + 11. Net load on brake 60 lbs. + 12. Corresponding effective power 11.6 B.H.P. + 13. Gas consumption per B.H.P. per hour at 24 deg. C. + and 721 mm. mean pressure. 21 cubic feet + 14. Gas consumption per B.H.P. per hour at 0 deg. C. + and 760 mm. mean pressure. 18.3 cubic feet + + RUNNING WITH NO LOAD WITH STREET-GAS + + 15. Number of revolutions per minute 206 + 16. Corresponding number of explosions 22 per cent. + 17. Total gas consumption per hour at 24 deg. C. + and 721 mm. mean pressure. 106 cubic feet + 18. Maximum calorific power of gas per cubic foot 598 B.T.U. + 19. Thermal efficiency with 96 per cent. explosions 31 per cent. + 20. Mechanical efficiency with 96 per cent. + explosions 82 per cent. + 21. Temperature of water at the jacket-inlet 75 degs. F. + 22. Temperature of water at the jacket-outlet 130 degs. F. + 23. Compression per square inch on piston surface 178 lbs. + 24. Pressure after expansion 37 lbs. + + + TEST OF WINTERTHUR PLANT WITH PRODUCER-GAS + + 1. Nature of fuel. Belgian anthracite, "Bonne + Esperance et Batterie"; size, 3/4 inch. + + 2. Chemical composition: Carbon, 86.5 per cent.; + hydrogen, 3.5 per cent.; oxygen and nitrogen, + 4.65 per cent.; ash, 5.35 per cent. + + 3. Calorific value per pound of coal 14200 B.T.U. + 4. Net calorific value per pound of fuel 15050 B.T.U. + 5. Price of anthracite delivered at the plant $3.50 per ton + 6. Number of revolutions of engine per minute 200 + 7. Corresponding number of explosions 91 per cent. + 8. Load on brake 106 lbs. + 9. Corresponding effective horse-power 20.2 B.H.P. + 10. Fuel consumption at the generator per hour 16.4 lbs. + 11. Fuel consumed per B.H.P. per hour 0.81 lbs. + 12. Proportion of ash resulting from the tests 6 per cent. + 13. Mean initial explosive pressure per square + inch 419.5 lbs. + 14. Average pressure on piston per square inch 72.5 lbs. + 15. Indicated horse-power with 91 per cent. + explosions 25.4 I.H.P. + 16. Mechanical efficiency 79 per cent. + 17. Thermal efficiency at the producer 22 per cent. + 18. Water consumption per hour in the scrubber 66 gals. + 19. Cost per B.H.P. per hour in anthracite 62 gals. + + + TEST OF A 60 B.H.P. GAS-ENGINE, TYPE G 9, WITH A SUCTION-GAS + PLANT OF THE GASMOTOREN FABRIK DEUTZ + + (Made at Cologne, March 15, 1904, by R. Mathot.) + + DATA OF THE TESTS + + Diameter of Piston = 16.5". Piston Stroke = 18.9" + + FULL LOAD + + 1. Average number of revolutions per minute 188.66 + 2. Corresponding effective work 65.11 B.H.P. + 3. Average compression per square inch 176 lbs. + 4. Average initial explosive pressure per square + inch 397 lbs. + 5. Average final expansion pressure 25 lbs. + 6. Vacuum at suction 4.4 lbs. + 7. Average pressure on piston 81 lbs. + 8. Corresponding indicated horse-power 77 I.H.P. + + FUEL + + 9. Nature of fuel: Anthracite coal 0.4" to 0.8" + 10. Origin: Coalpit of Zeihe, Morsbach at Aix-la-Chapelle. + 11. Chemical composition of coal: + Carbon 83.22% + Hydrogen 3.31% + Nitrogen and Oxygen 3.01% + Sulphur 0.44% + Ash 7.33% + Water 2.69% + 12. Calorific value. 13650 B.T.U. + + GAS + + 13. Chemical composition of gas: + Carbonic acid 6.60% + Oxygen 0.30% + Hydrogen 18.90% + Methane 0.57% + Carbon monoxide 24.30% + Nitrogen 49.33% + 14. Calorific value of gas, combination water, + at 59 deg. F. constant volume reduced to 32 deg. F. + and atmospheric pressure 140 B.T.U. + + TEMPERATURES + + _Engine_ + + 15. Cooling water at the inlet of the + cylinder-head 55.4 deg. F. + Temperature at the outlet 109.5 deg. F. + 16. Temperature at outlet of cylinder 127.5 deg. F. + + _Gas-Generator_ + + 17. Temperature of water in the vaporizer 158.3 deg. F. + + EFFICIENCIES AND CONSUMPTION + + 18. Mechanical efficiency 84.6% + 19. Gross consumption of coal per B.H.P. per hour 0.86 lbs + 20. Thermal efficiency in proportion to the + effective work and the gross consumption + of coal in the gas-generator 24.3% + + HALF LOAD + + WORK + + 1. Average number of revolutions per minute 195.5 + 2. Corresponding effective work 33.85 B.H.P. + 3. Corresponding average compression 125 lbs. + 4. Average initial explosive pressure 258 lbs. + 5. Average final expansion 18 lbs. + 6. Vacuum at suction 6.8 lbs. + 7. Average mean pressure on piston 46.2 lbs. + 8. Corresponding indicated power 45. I.H.P. + 9. Speed variation between full and half load 3.5% + + CONSUMPTION + + 10. Gross consumption of coal per B.H.P. per hour 1.155 lbs. + + RUNNING WITH NO LOAD + + 1. Average number of revolutions per minute 199 + 2. Minimum corresponding compression 95.55 lbs. + 3. Average initial explosive pressure 220 lbs. + 4. Average final expansion 0 lbs. + 5. Vacuum at suction 8.8 lbs. + 6. Average pressure on piston 11.2 lbs. + 7. Corresponding indicated horse-power. 11 I.H.P. + 8. Speed variation between full load and no load 5.2% + + + TEST OF A GAS PLANT OF A FOUR-CYCLE DOUBLE-ACTING + ENGINE OF 200 H.P. AND A SUCTION-PRODUCER IN THE + WORKS OF THE GASMOTOREN FABRIK DEUTZ, COLOGNE + +March 14 and 15, 1904, by Messrs. A. Witz, R. Mathot, and de Herbais + +DATA OF THE TESTS + +Piston Diameter: 21-1/4". Stroke: 27-9/16". Diameter of Piston-Rods: +front, 4-3/4"; rear, 4-5/16" + + ENGINE + +_Full Load Tests_ + + 1. Average number of revolutions per minute 151.29 and 150.20 + 2. Corresponding effective load 214.22 B.H.P. + and 222.83 B.H.P. + 3. Duration of the tests 3 hours and 10 hours + 4. Average temperature of water after cooling + the piston 117.5 deg. F. + 5. Average temperature of water after cooling + the cylinder and valve-seats 135 deg. F. + 6. Water consumption per hour for cooling the + piston 39 gal. + + PRODUCER + + 7. Nature and Origin of Fuel: Anthracite coal + "Bonne-Esperance et Batterie" Herstal, + Belgium. + 8. Calorific value of fuel 14650 B.T.U. + 9. Consumption of fuel per hour (plus 53 lbs. + on the night of the 14th for keeping the + generator fired during 14 hours, the + engine being stopped) 199 lbs.-160 lbs. + 10. Water consumption per hour in the vaporiser 14.2 gals. + 11. Water consumption per hour in the scrubbers 318 gals. + 12. Average temperature of gas at the outlet + of the generator 558 deg. F. + 13. Average temperature of gas at the outlet + of the scrubbers 62.5 deg. F. + + EFFICIENCIES + + 14. Gross consumption of coal per B.H.P. per hour 0.927 lbs.-0.720 lbs. + 15. Consumption of coal per B.H.P. after deduction + of the water 0.907 lbs.-0.705 lbs. + 16. Thermal efficiency relating to the effective + H.P. and to the dry coal consumed in the + generator 19%-24.4% + 17. Water consumption per B.H.P. hour: + For the cylinder, stuffing-boxes and + valve-seat jackets 4.65 gals. + For the piston and piston-rods 1.75 gals. + For the vaporizer 0.0655 gals. + For washing the gas in the scrubbers 1.42 gals. + 18. Water converted in steam per lb. consumed + in the generator 0.193 gals. + + + + + INDEX + + + A + +Adjustment of gas-engine, 126 + +Adjustment of moving parts, imperfect, 146 + +Admission-valve, binding of, 152 + +Admission, variable, 55, 56 + +Air-blast, 180 + +Air-chest, 82 + +Air, displacement of, 92 + +Air, exclusion of, in producers, 207 + +Air, filtration of, 82 + +Air-heater, Winterthur, 236 + +Air-heaters, 238 + +Air-pipe, 82 + +Air-pipe, location of, 83 + +Air-pump, 266 + +Air, regulation of supply, 82 + +Air suction, 81 + +Air suction, resistance to, 82 + +Air supply of producer, 225 + +Air-valve, control by engine, 25 + +Air vibration, 92 + +Alcohol as engine fuel, 264 + +Anthracite, consumption of, in producers, 200 + +Anthracite in producers, 190, 201 + +Anti-pulsators, 77 + +Anti-pulsators, disconnection of, in stopping engine, 132 + +Anti-pulsators, precautions to be taken with, 79 + +Anti-vibratory substances, 89 + +Ash-pit, 214, 217 + +Ash-pit, Bollinckx, 220 + +Ash-pit, cleaning of, 261 + +Ash-pit, Deutz, 220 + +Ash-pit, door of, 220 + +Ash-pit, Wiedenfeld, 220 + +Asphyxiation, 169 + +Atomizer of oil-engines, 265 + + + B + +Back firing, 82, 131 + +Back pressure to exhaust, 151 + +Bags, arrangement of, 80 + +Bags, capacity of, 79 + +Bags, precautions to be taken with, 79 + +Bags, rubber, 77 + +Bark as producer fuel, 193 + +Batteries for ignition, 31 + +Bearings, adjustability of, 5 + +Bearings, adjustment of, 44 + +Bearings, care of, 123 + +Bearings, lubrication of, 117 + +Bearings, material of, 51 + +Bearings of fly-wheels, 92 + +Bearings, overheated, 146 + +Bearings, over-lubricated, 150 + +Bearings, position of, 44 + +Bell, gas-holder, 187 + +Bell, Pintsch, 248 + +Bell, volume of, 187 + +Belts, prevention of adhesion by oil, 120 + +Benier, E., 199 + +Benzin as engine fuel, 264 + +Binding, 147 + +Blast in producers, 180, 193, 225 + +Blower, Koerting, 181 + +Blower, Root, 182, 188 + +Blowers for producers, 181 + +Blowing-generators, 169 + +Bolts of foundation, 91 + +Bomb, Witz, 284, 292 + +Boughs for coolers, 108 + +Box, charging, 221 + +Box, double closure for charging, 222 + +Box, removable charging, 225 + +Brake tests, 284 + +Branch pipes, minimum diameter of, 81 + +Bricks for foundation, 91 + +Brushes, lifting of, when dynamo-engine is stopped, 132 + +Brush, purifying, 250 + +Burner of hot tube, how ignited, 128 + +Burner, regulation of fixed, 144 + +Bushings, care of, 123 + +Bushings, fusion of, 147 + +Bushings (see also Bearings) + + + C + +Calorimeter, Witz, 292 + +Calorimeters, 284, 290 + +Cam, half-compression, 130, 132 + +Cam, relief, 130 + +Cams, 51 + +Caps of valve-chests, 124 + +Carbureter, 266 + +Care during operation of engine, 131 + +Casing, independence of frame, 42 + +Charging a producer, 221 + +Charging the generator, 259 + +Chest for exhaust, 83 + +Circulation of water, 98, 125 + +Circulation of water, how effected, 102 + +Circulation of water in tanks, 105 + +Circulation of water, regulation of, 107 + +Cleaning of producer, 261 + +Cleanliness, necessity of, 121 + +Cleanliness of producers, 179 + +Closures for charging-boxes, 223 + +Coal in producers, 201 + +Coal in producers, bituminous, 195 + +Coal, Pennsylvania, 203 + +Coal (see also Anthracite) + +Coal, Welsh, 203 + +Cock, Deutz, 224 + +Cock, Pierson, 224 + +Cock for charging-box, 223, 224 + +Coke in producers, 201 + +Coke in washers, 242 + +Combustion-generators, 193 + +Combustion, inverted, 195 + +Compression, determination of, 273 + +Compression, faulty, 134 + +Compression, high, 154 + +Compression in Banki engine, 264 + +Compression in Diesel engine, 264 + +Compression, losses in, 143 + +Compression period, 21 + +Compression, relation to power developed, 122 + +Compressors for producers, 182 + +Connecting-rod bearings, 45 + +Connecting-rod bearings, rational design of, 45 + +Connecting-rod, lubrication of, 113, 115 + +Consulting engineer, advisability of retaining, 282 + +Consumption at half load and full load, 62 + +Consumption at various loads, 62 + +Consumption in double or triple acting engines, 62 + +Consumption of gas, 173 + +Consumption of gas in burner, 30 + +Consumption of suction-producers, 200 + +Consumption per effective horse-power, 62 + +Cooler for gas, 199 + +Cooler, for producer, 240 + +Coolers, 107 + +Coolers, size of, 109 + +Cooling of cylinder, 98, 100, 156 + +Cooling of producer-gas engines, 203 + +Cooling, thermo-siphon, 100 + +Cost of oil and volatile hydrocarbon engines, 268 + +Crank-pin, tensile strength of, 51 + +Crank-shaft, 50, 51 + +Crank-shaft bearings, 44 + +Crank-shaft bearings, design of, 46 + +Crank-shaft, effect of premature explosion on, 30 + +Crank-shaft lubrication, 117 + +Crank-shaft, material of, 50 + +Crosshead, care of, 123 + +Cycle, analysis of, 276 + +Cylinder, arrangement of, 41 + +Cylinder, cleaning of, 122 + +Cylinder, cooling of, 156 + +Cylinder, evacuation of, 83, 131 + +Cylinder, gravel in, 137 + +Cylinder, grinding of, 42 + +Cylinder, incandescent particles in, 142 + +Cylinder, independence of casing, Compression in, 42 + +Cylinder-jacket (see Water-jacket) + +Cylinder lubrication, 112 + +Cylinder-oil, 112, 149 + +Cylinder, overhang in horizontal engines, 42 + +Cylinder, overheating of, 148 + +Cylinder, presence of water in, 136 + +Cylinder-shell, 41 + +Cylinder, smoke from, 149 + +Cylinder, temperature during operation of engine, 132 + +Cylinder, thrust of, 43 + +Cylinder, tightness of, 122 + + + D + +Damper, Pintsch, 224 + +Dampers, 223 + +Detonations, untimely, 141 + +Distributing mechanism, derangement of, 152 + +Drain-cock in gas-pipes, 70, 75 + +Drain-cocks, testing of, 256 + +Drier for producer-gas, 248 + +Dust-collector, 239 + +Dust-collector, Benz, 239 + +Dust-collector, Bollinckx, 239 + +Dust-collector, Pintsch, 239 + +Dust-collector, Wiedenfeld, 239 + +Dynamo, lifting brushes from, in stopping engine, 132 + + + E + +Ebelmen principle, 195 + +Engine, Banki, 264 + +Engine, Diesel, 264 + +Engine, producer-gas and steam, compared, 203 + +Engine, selection of, 279 + +Engine, starting a producer-gas, 258 + +Engineer, duty of a consulting, 281 + +Engines, governing oil, 265 + +Engines, oil, 264, 265 + +Engines, producer-gas, 153 + +Engines, producer-gas, temperature of, 157 + +Engines, specifications of, 281 + +Engines, speed of oil, 264 + +Engines, tests of, 268 + +Engines, volatile hydrocarbon, 264, 267 + +Engines, writers on oil, 266 + +Escape-pipes, 228 + +Essences, 264 + +Exhaust, 83 + +Exhaust, back pressure to, 151 + +Exhaust, determination of resistance to, 274 + +Exhaust into sewer or chimney, 85 + +Exhaust, noises of, 94, 141 + +Exhaust period, 22 + +Exhaust, water in, 136 + +Exhausters, 183 + +Exhaust-chest, 83 + +Exhaust-muffler, 86, 94 + +Exhaust-pipe, 83, 85 + +Exhaust-pipe, design of, 96, 97 + +Exhaust-pipe, joints for, 85 + +Exhaust-pipe, oil in, 151 + +Exhaust-valve, binding of, 152 + +Exhaust-valve, cooling of, 25 + +Expansion-boxes, 95 + +Expansion period, 22 + +Expert, necessity of an, 282, 283 + +Explosion, spontaneous, 140 + +Explosion-engines (see Gas-engines) + +Explosion period, 22 + +Explosion-recorder, analysis of inertia of, 277 + +Explosion-recorder for industrial engines, 285 + +Explosion-recorder, the continuous, 269 + +Explosions, comparison of average force of, 275 + +Explosion-records, 288 + +Explosions, retarded, 143 + + + F + +Fans for producers, 181 + +Feeder, Winterthur, 236 + +Feed-hopper, 224 + +Fire-box, door of, 221 + +Flues, escape, 228 + +Fly-wheel, oil on, 120 + +Fly-wheel, starting the, 131 + +Fly-wheels, 46 + +Fly-wheels as pulleys, 46 + +Fly-wheels, balancing of, 46 + +Fly-wheels, curved spoke, how mounted, 49 + +Fly-wheels, fastening of, 46 + +Fly-wheels, proper mounting of, 46 + +Fly-wheels, rim of, 46 + +Fly-wheels, single, 48, 92 + +Fly-wheels, single, for dynamo-engines, 46 + +Fly-wheels, straight and curved spoke, 49 + +Fly-wheels with hit-and-miss system, 50 + +Foundation, 44, 87 + +Foundation, design of, 88, 89 + +Foundation, excavation for, 88 + +Foundation, insulation of, 89, 90 + +Foundation of dynamo-engine, 91 + +Frame, 43 + +Frame, method of securing, to foundation, 44 + +Fuel of producers, 178, 187, 254 + +Fuel, qualities of, 201 + +Fuel (see also Lignite, Peat, Sawdust, Wood, Coal, etc.) + +Fuel, size of, 201 + +Fuel, smoke-producing, 254 + + + G + +Gas, ascertaining purity of, 128 + +Gas, blast-furnace, 153 + +Gas, calorific value of, 284 + +Gas, calorific value of producer, 200 + +Gas, coke-oven, 153 + +Gas consumption, 173 + +Gas consumption of burner, 30 + +Gas, effect of quality, 152 + +Gas-engine, balancing of, 46 + +Gas-engine, care during operation, 131 + +Gas-engine, cost of installation, 19 + +Gas-engine, cost of operation, 19 + +Gas-engine, difficulties in starting, 134 + +Gas-engine, how to start a, 128 + +Gas-engine, how to stop a, 132 + +Gas-engine, installation of a, 68 + +Gas-engine, location of a, 68 + +Gas-engine, selection of a, 21 + +Gas-engine, simplicity of installation, 17 + +Gas-engine, the four-cycle, 21 + +Gas-engines, adjustment of, 126 + +Gas-engines, care of, 121 + +Gas-engines, "Steam-Hammer," 57 + +Gas-engines, temperature of, 158 + +Gas-engines, tests of, 283 + +Gas-engines, vertical, 56 + +Gas-engines, writers on, 68 + +Gas, fuel, 153 + +Gas-holder, 186, 189 + +Gas-holders, 247 + +Gas-holder, combined with washer or scrubber, 186 + +Gas, illuminating (see Street-gas) + +Gas, impurities of, 172 + +Gas, Mond, 153, 167 + +Gasometer (see Gas-holder) + +Gas, producer (see Producer-gas) + +Gas production, 173 + +Gas, purification of wood, 195 + +Gas supply, necessity of coolness, 69 + +Gas-valve, necessity of independent operation of, 27 + +Gas, water, 153, 169 + +Gas, wood, 153, 168 + +Gases, analysis of, 290 + +Generator (see also Producer) + +Generator, Benz, 207 + +Generator, Bollinckx, 207 + +Generator, care of, 259 + +Generator, charging the, 259 + +Generator, construction of, 177, 207 + +Generator, dimensions of, 252 + +Generator, Dowson, 177 + +Generator, firing the, 205, 256 + +Generator, hot operation of, 252 + +Generator of suction producer, 205 + +Generator, operation of, 251 + +Generator, Pierson, 215 + +Generator, Pintsch, 207 + +Generator, Taylor, 207 + +Generator, Wiedenfeld, 207 + +Generator, Winterthur, 207 + +Generator with internal vaporizer, 206 + +Generators, blowing, 169 + +Generators, pressure, 169, 177 + +Governor, ball, 52, 53 + +Governor, care during operation, 131 + +Governor, hit-and-miss, 52, 54 + +Governor, inertia, 53 + +Governor, sensitiveness of, 52 + +Governors, 53 + +Governors, adjustment of, 124 + +Governors, care of, 123 + +Governors, centrifugal, 56 + +Governors, centrifugal, with hit-and-miss regulation, 55 + +Governors for oil-engines, 265 + +Governors for producer-gas engines, 161 + +Governors, hit-and-miss, 54 + +Governors, variable admission, 56 + +Grate, Benier's, 216 + +Grate of generator-lining, 214 + +Grate, Kiderlen, 216 + +Grate, Pintsch, 216 + +Grate, Wiedenfeld, 216 + + + H + +Heater, air, 238 + +Hit-and-miss regulation (see Governors) + +Holders, gas, 247 + +Hopper, Bollinckx, 225 + +Hopper, Deutz, 225 + +Hopper for generator, 224 + +Hopper, removable feed, 225 + +Hopper, Taylor, 225 + +Hopper, Wiedenfeld, 225 + +Hopper, Winterthur, 225 + +Horse-power, definition of, 60 + +Horse-power, determination of, 61 + +Horse-power (see also Power) + +Hot tubes (see Tubes) + +Hydrocarbons, volatile, for engine fuel, 264 + + + I + +Ignition, 27, 122 + +Ignition, adjustment of, 144 + +Ignition by battery and coil, 31 + +Ignition by magneto, 33 + +Ignition, curing defects of electric, 145 + +Ignition, defective, 152 + +Ignition, disadvantages of belated, 28 + +Ignition, disadvantages of premature, 28 + +Ignition, effect of lost motion, 146 + +Ignition, effect of mixture composition on, 28 + +Ignition, effect of temperature of flame on, 28 + +Ignition, effect of water on, 136 + +Ignition, electric, 30, 139 + +Ignition, electric, regulation of, 145 + +Ignition, faulty, 143 + +Ignition for high-pressure engines, 35 + +Ignition, hot-tube, 159 + +Ignition, imperfect, 137 + +Ignition, objections to electric, 31 + +Ignition of producer-gas, 160 + +Ignition, premature, 139, 142 + +Ignition, premature, in high-pressure engines, 158 + +Ignition, prevention of, by faulty compression, 134 + +Ignition, proper timing of, 27 + +Ignition, spontaneous, 140, 159 + +Ignition, tests prior to starting engine, 129 + +Ignition-tubes (see Tubes) + +Incrustation of water-jacket, 98, 148 + +Incrustation, prevention of, 107 + +Incrustations, 255 + +Indicators, 285 + +Indicator-records, 127 + +Induction-coil, 32 + +Installation, laws governing gas-engine, 86 + + + J + +Joints, 125 + +Joints, care of, 124 + + + L + +Laming mass, 246 + +Laws governing gas-engines, 86 + +Leakage of pipes, 69 + +Lift-valve for charging-box, 223 + +Lignite in producers, 188 + +Lining, refractory, 211 + +Lining, support for generator, 214 + +Loads, consumption at half and full, 62 + +Location of engine, 68 + +Lubricate (see Oils) + +Lubricating-pumps, 115 + +Lubrication, 111, 121 + +Lubrication, difficulties entailed by, 119 + +Lubrication, faulty, 149 + +Lubrication of crank-shaft, 117 + +Lubrication of high-power engine, 116 + +Lubrication of valve-stem, 119 + +Lubricator, cotton-waste, 117 + +Lubricators, automatic, 113 + +Lubricators, disconnection of, when stopping engine, 132 + +Lubricators, examination of, before starting, 129 + +Lubricators, feed of, 121 + +Lubricators, revolving-ring, 118 + +Lubricators, sight-feed, 118 + +Lubricators, types of, 113 + + + M + +Magneto, adaptability for producer-gas, 35 + +Magneto, control of, 38 + +Magneto, efficiency of, 34 + +Magneto-igniter, construction of, 35 + +Magneto ignition, 33 + +Magneto ignition, precautions to be taken, 34 + +Magneto, inspection of, before starting engine, 129 + +Magneto, mechanical control of, 33 + +Magneto, operation of, 33 + +Magneto, regulation of, 37 + +Maintenance of plants, 295 + +Manograph, 269 + +Mass, Laming, 246 + +Meters, capacity of, 70 + +Meters, dry, 72 + +Meters, evaporation in wet, 70 + +Meters, falsification of records, 70 + +Meters, inclination of, 71 + +Meters, size of, 71 + +Misfire, 137 + +Mixture, effect of high compression in, 155 + +Mixture, effect of high pressure on, 156 + +Mixture, governing by varying the, 161-164 + +Mixture, poorness of, 143 + +Mixture, pressure of, 26 + +Mixture-valve, necessity of independence of operation of, 27 + +Mortar for foundation, 87 + +Motion, lost, 146 + +Muffler for exhaust, 86, 94 + + + N + +Naphthalene in gas-pipes, 70 + +Noises, cause of, 92 + +Noises of exhaust, 94 + + + O + +Oilers (see Lubricators) + +Oiling (see Lubrication) + +Oil, addition of sulphur to, 147 + +Oil, cylinder, 149 + +Oil-engines, 264, 265 + +Oil-engines, governing, 265 + +Oil-engines, speed of, 264 + +Oil-engines, writers on, 266 + +Oil for engine fuel, 264 + +Oil, freezing of, 150 + +Oil-guard for fly-wheel, 120 + +Oil-lamp, 266 + +Oil, prevention of spreading on fly-wheel, 120 + +Oil-pumps, 115, 226 + +Oil, quality of, 150 + +Oil, splashing of, 119 + +Oil-tank, 266 + +Oils, how tested, 112 + +Oils, mineral for lubrication, 112 + +Oils, purification of, 113 + +Oils, quality of, 112 + +Oils, requisites of, 112 + +Operation, steadiness of, 52 + +Otto cycle, 21 + +Overheating, 152 + +Overheating, prevention of, 147 + + + P + +Pacini treatment, 171 + +Peat in producers, 188 + +Perturbations, 134 + +Petrol (see Oil) + +Pipe-hangers, 86 + +Pipes, 69 + +Pipes, cross-section of, 70 + +Pipes, disposition of, 77 + +Pipes, escape, 228 + +Pipes, exposure to cold, 69 + +Pipes for exhaust, 83 + +Pipes for producer-gas, 249 + +Pipes for water-tanks, 102, 103, 105 + +Pipes, hanging of, 86 + +Pipes, insulation from foundations and walls, 94 + +Pipes, leakage of, 69 + +Pipes, minimum diameter of branch, 81 + +Pipes, proper size of, 70 + +Piston, 39, 122 + +Piston, avoidance of insertions or projections, 39 + +Piston, cleaning of, 141 + +Piston, curved faces inadvisable, 39 + +Piston, direct connection with crank-shaft, 43 + +Piston, finish of, 41 + +Piston, importance of, 111 + +Piston, leakage of, 136 + +Piston, overheating of, 148 + +Piston, position of, in starting, 130 + +Piston, rear face of, 39 + +Piston-pin, construction of bearing at, 40 + +Piston-pin, location of, 41 + +Piston-pin, locking of, 40 + +Piston-pin, lubrication of, 113 + +Piston-pin, material of, 40, 51 + +Piston-pin, strength of, 40 + +Piston-rings, fouling of, 149 + +Piston-rings, material of, 41 + +Piston-rings, number of, 41 + +Piston-rod, effect of premature explosion on, 30 + +Piston-wear, 40 + +Poisoning, carbon monoxide, 170 + +Porcelain of spark-plug, 32 + +Power, definition of, 60 + +Power, measuring engine, 285 + +Power, "Nominal," 61 + +Precautions to be taken in starting, 128 + +Pressure, back, to exhaust, 151 + +Pressure-generators, 169, 177 + +Pressure in producer-gas engines, 160 + +Pressure-lubricators, 114 + +Pressure-producers, 174 + +Pressure-regulator, bell as, 187 + +Pressure-regulators, 77 + +Pressure-regulators, their construction, 78 + +Pressures, high, in producer-gas engines, 154 + +Preheaters, 229 + +Producer, assembling, 253 + +Producer, Benier, 216 + +Producer, Benz, 228, 239, 240 + +Producer, Bollinckx, 206, 220, 225, 228, 234, 239 + +Producer, Chavanon, 229 + +Producer, cleaning of, 261 + +Producer, Dawson, 174 + +Producer, Deschamps, 198 + +Producer, Deutz, 206, 220, 224, 225, 228, 229, 240 + +Producer, Deutz, 231, 232 + +Producer, Deutz lignite, 188 + +Producer, Duff, 195 + +Producer, Fange-Chavanon, 198 + +Producer, Fichet-Heurty, 240, 245 + +Producer, Gardie, 183 + +Producer-gas, 153 + +Producer-gas, 165 + +Producer-gas as a furnace fuel, 177 + +Producer-gas, calorific value of, 200 + +Producer-gas, composition of, 166 + +Producer-gas plants, tests of, 297 + +Producer-gas, writers on, 154 + +Producer, general arrangement of suction, 204 + +Producer, Goebels, 206 + +Producer, Hille, 206, 239 + +Producer, Kiderlen, 206 + +Producer, Kiderlen, 216 + +Producer, Koerting, 232 + +Producer, Lencauchez, 212, 214 + +Producer, Phoenix, 217 + +Producer, Pierson, 224, 229 + +Producer, Pintsch, 206, 216, 224, 231, 232, 239, 245, 248 + +Producer, Riche, 168, 190, 193, 195, 216 + +Producer (see also Generator) + +Producer, stoppage of, 261 + +Producer, Taylor, 206, 214, 225, 231, 232 + +Producer, test by smoke, 254 + +Producer, test of Deutz, 298 + +Producer, test of Dowson, 296 + +Producer, tests of Winterthur, 297 + +Producer, Thwaite, 195 + +Producer, Wiedenfeld, 206, 216, 220, 225, 234, 239 + +Producer, Winterthur, 225, 228, 236 + +Producers, advantages of suction, 199 + +Producers, combustion, 193 + +Producers, conditions of perfect operation, 251 + +Producers, consumption of suction, 200 + +Producers, distilling, 190 + +Producers, efficiency of, 201 + +Producers, efficiency of lignite, 190 + +Producers, efficiency of wood, 194 + +Producers, lignite, 188 + +Producers, maintenance of, 254 + +Producers, peat, 188 + +Producers, pressure, 174 + +Producers, self-reducing, 193 + +Producers, specifications of, 281 + +Producers, suction, 199 + +Producers, suction (see also Suction-producers) + +Producers, tests of, 297 + +Producers with external vaporizers, 206 + +Production of gas, 173 + +Pulley, disconnection of, in stopping engine, 132 + +Pump, circulating with by-pass, 106 + +Purifier, fiber, 185 + +Purifier, Fichet-Heurtey, 245 + +Purifier, material for, 245 + +Purifier, moss, 185 + +Purifier, Pintsch, 245 + +Purifier, sawdust, 185 + +Purifiers for gas, 184 + +Purifiers for producer-gas, 244 + + + R + +Recorder, analysis of inertia of explosion, 277 + +Recorder, explosion, for industrial engines, 285 + +Recorder, the continuous explosion, 269 + +Records of engines, 284 + +Records of explosions, 288 + +Records, indicator, 127 + +Regrinding of valves, 122 + +Regularity, cyclic, 48, 53 + +Remagnetization of magnetos, 33 + +Resuscitation after asphyxiation, 171 + +Retort, cleaning of, 225 + +Retort of producer, 190 + +Retort, support, 214 + +Revolutions, variations in number of, 52 + +Rollers, 51 + +Running, steadiness of, 52 + + + S + +Sand for foundation, 87 + +Sawdust in producers, 193 + +Scavenging, 142, 155 + +Scrubber, 189, 199 + +Scrubber, combined with gas-holder, 186 + +Scrubber for producer-gas, 240 + +Scrubber, size of, 253 + +Selection of gas-engine, 21 + +Shavings in producers, 193 + +Slide-valve for charging-box, 223 + +Slide-valve, its disadvantages, 23 + +Sluice-valves, 101 + +Smoke from cylinder, 149 + +Spark-plug, 32 + +Specifications of engines, 281 + +Specifications of producers, 281 + +Speed, how to increase, 124 + +Speed of oil-engines, 264 + +Speed of volatile hydrocarbon engines, 264 + +Speed, variation of, with load, 52 + +Spokes of fly-wheels, 49 + +Spring for valves (see Valves) + +Springs, selection of, for explosion-recorder, 277 + +Starter, Tangye, 65 + +Starting an engine, 128 + +Starting, automatic, 63, 130 + +Starting by compressed air, 64 + +Starting by hand, 63 + +Starting by hand-pumps, 64 + +Starting, difficulties in, 134 + +Starting, how accomplished, 66 + +Starting of producer-gas engine, 258 + +Steadiness, 52 + +Steam-engine, cost of installation, 19 + +Steam-engine, cost of operation, 19 + +Stoppage of producer, 261 + +Stopping the engine, 132 + +Stops, sudden, 151 + +Straw in producers, 193, 254 + +Street-gas, 165 + +Suction, determination of resistance to, 274 + +Suction, noises caused by, 141 + +Suction of air, 81 + +Suction period, 21 + +Suction-producer, general arrangement of, 204 + +Suction-producers, 199 + +Suction-producers, advantages of, 199 + +Suction-producers, efficiency of, 201 + +Suction-valve, leakage of, 142 + +Super-heater, Winterthur, 236 + +Sylvester treatment, 171 + + + T + +Tanks, connection of, 105 + +Tanks, design of, 103 + +Tanks, location of, 102 + +Tanks for water-jacket, how mounted, 101 + +Tar in producer-plants, 200 + +Tar, removal of, 250 + +Tar (see also Scrubber, Purifier, etc.) + +Taylor, A., 199 + +Terminals of magneto apparatus, 34 + +Tests of gas-engine plants, 283 + +Tests of high-speed engines, 268 + +Tests of producer-gas engines, 297 + +Thrust-bearings, 51 + +Tongue, traction of, in asphyxiation cases, 172 + +Tower, washer, 244 + +Town-gas (see Street-gas) + +Tree branches for coolers, 107 + +Trepidations, 92 + +Tube, gas-supply pipe of incandescent, 77 + +Tube, incandescent, 27 + +Tube, incandescent, adjustment of, 144 + +Tube, incandescent, breakage of, 137 + +Tube, incandescent, danger of breaking, 131 + +Tube, incandescent, how started, 128 + +Tube, incandescent, leakage of, 138 + +Tubes as vaporizers, 231 + +Tubes, incandescent, 28, 159 + +Tubes, incandescent, valved, 29 + +Tubes, use of special valves with incandescent, 29 + +Tubes, valveless ignition, 28 + + + V + +Valve-chests, 124 + +Valve mechanism, slide, 23 + +Valve-regrinding, 122, 135 + +Valve-stem lubrication, 119 + +Valves, 122 + +Valves, accessibility of, 25 + +Valves, cooling of, 25 + +Valves, cooling of, in high-pressure engines, 156 + +Valves, defective operation of, 135 + +Valves, free, 27 + +Valves, mechanical control of, 27 + +Valves, modern, 24 + +Valves, necessity of cleanliness, 25 + +Valves, regulation of, before starting, 129 + +Valves, requisites of, 25 + +Valves, retardation in action of, 146 + +Vaporizer, Bollinckx, 234 + +Vaporizer, Chavanon, 229, 234 + +Vaporizer, Deutz, 231, 232, 229, 225 + +Vaporizer, Field, 233 + +Vaporizer, internal, 206 + +Vaporizer, Koerting, 232 + +Vaporizer, maintenance of, 255 + +Vaporizer, operation of, 234 + +Vaporizer, Pierson, 229 + +Vaporizer, Pintsch, 231, 232 + +Vaporizer-preheaters, 229 + +Vaporizer, size of, 253 + +Vaporizer, Taylor, 231, 232 + +Vaporizer, Wiedenfeld, 225, 234 + +Vaporizers, external, 206, 230 + +Vaporizers, internal, 229 + +Vaporizers, partition, 234 + +Vaporizers, regulation of, 236 + +Vaporizers, tubular, 231 + +Ventilation in engine-room, 69 + +Vibration, 89 + +Vibration of air, 92 + +Vibration, prevention of, 89, 90 + + + W + +Water circulation, 98, 107, 125 + +Water circulation by pump, 107 + +Water circulation, care during operation, 132 + +Water circulation, how effected, 102 + +Water circulation, prevention of freezing, 133 + +Water-coolers, 106 + +Water-coolers, size of, 109 + +Water for circulation, 99 + +Water for producer-gas engines, 203 + +Water-gas, 153, 167 + +Water in cylinder, 136 + +Water in exhaust, 136 + +Water-jacket, 41, 98, 125, 157 + +Water-jacket, incrustation of, 148 + +Water-jacket, outlet of, 98 + +Water-jacket, prevention of incrustation, 107 + +Water-pipe, 102 + +Water, purification of, for circulation, 98 + +Water, running, for jacket, 98 + +Water-tanks, 101 + +Water-tanks, connection of, 103, 105 + +Water-tanks, design of, 103 + +Water-tanks, location of, 102 + +Washer, Benz, 240 + +Washer, combined with gas-holder, 186 + +Washer, Deutz, 240 + +Washer, Fichet-Heurtey, 240 + +Washer for gas, 199 + +Washer for producer-gas, 240 + +Washer, maintenance of, 256 + +Washer, material employed in, 242 + +Washer, Winterthur, 240 + +Washers, 184 + +Wear, premature, 146 + +Witz apparatus, 284 + +Wood as fuel, 254 + +Wood, calorific value, 194 + +Wood-gas, 153, 168 + +Wood-gas, purification of, 195 + +Wood in producers, 190, 192, 193 + +Work, definition of effective, 60 + + + + + ADVERTISEMENTS + + + THE MIETZ & WEISS + + OIL ENGINE + + STATIONARY MARINE + 1 to 75 H.P. 1 to 60 H.P. + + [Illustration] + + 50 H.P. 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SPLITDORF 17-27 Vandswater Street, | + | New York, N.Y. | + |__________________________________________________________________| + | | + | [Illustration] | + | | + | CHEAPEST POWER SUCTION | + | | + | Gas Producers | + | | + | DR. OSKAR NAGEL | + | | + | 90 Wall Street NEW YORK | + |__________________________________________________________________| + | | + | E.H. KELLOGG & CO. Established 1858 | + | | + | Sole Manufacturers of the | + | World Renowned | + | | + | [Illustration] OILS [Illustration] | + | | + | Best Grades Lubricants | + | | + | Railway, Dynamo, | + | Gas Engine, Ice | + | Machine, Steamship | + | | + | New York, Liverpool, London, Bremen, 243 & 244 South St., | + | Hamburg, Bombay, Calcutta. New York, U.S.A. | + |__________________________________________________________________| + + ______________________________________________________ + | | + | Suction Gas Producers | + | and Backus Gas Engines | + | | + | One Horse Power With 1-1/4 lbs. 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Illustrations may have been moved. +The following publishers' errors and inconsistencies were corrected +as noted: + + Fig. 59: "Thermo-siphon" was "Thermo-syphon". + Page viii: "If ignition occurs too" was "If ignition occur too" + Page 18: "smoke-stack" was "smokestack". + Page 19: Split illustrations and titled one "Fig. 1a". + Page 70: Rearranged table. + Page 83: "sawdust" was "saw-dust". + Page 83: "9 feet by 15 feet" was "9 feet by 75 feet" (math error). + Page 92: "crank-shaft" was "crankshaft". + Page 92: "fly-wheel" was "flywheel". + Page 105: "thermo-siphons" was "thermo-syphons". + Page 128: "gas-pipe" was "gaspipe". + Page 174, 200, 203(2 places): "horse-power" was "horsepower". + Page 205: "super-heater" was "superheater". + Page 220: "air-tight" was "airtight". + Page 239: "superheated" was "super-heated". + Page 255: "potash" was "postash". + Page 264: "59 degrees F." was "490 degrees F." (conversion error). + Page 269: "drum p''" was "drum p'". + Page 291: Fig. 150 has been split into two figures. + Page 297: "Stroke" was "Stoke". + Page 300: "Ziehe was "Zi he". + Page 301: "Messrs." was "Me rs.". + Page 323: "FOR" was "FOF". + Index: "Fire-box" was "Firebox". + Index: "Governors, ... hit-and-miss" was "hit-and miss". + Index: "Piston ... crank-shaft" was "crankshaft". + Advertisements: Chapter header "ADVERTISEMENTS" added. + + * * * * * + + + + + +End of the Project Gutenberg EBook of Gas-Engines and Producer-Gas Plants, by +R. E. 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