Read Ebook: True Stories of the Great War Volume 2 (of 6) Tales of Adventure--Heroic Deeds--Exploits Told by the Soldiers Officers Nurses Diplomats Eye Witnesses by Miller Francis Trevelyan Editor

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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

THE INSTALLATION OF AN ENGINE

Location.--Gas-Pipes.--Dry Meters.--Wet Meters.--Anti-Pulsators, Bags, Pressure-Regulators.--Precautions.--Air Suction.-- Exhaust.--Legal Authorization 69

FOUNDATION AND EXHAUST

The Foundation Materials.--Vibration.--Air Vibration, etc.-- Exhaust Noises 87

WATER CIRCULATION

Running Water.--Water-Tanks.--Coolers 98

LUBRICATION

Quality of Oils.--Types of Lubricators 111

CONDITIONS OF PERFECT OPERATION

General Care.--Lubrication.--Tightness of the Cylinder.-- Valve-Regrinding.--Bearings.--Crosshead.--Governor.--Joints.-- Water Circulation.--Adjustment 121

HOW TO START AN ENGINE.--PRELIMINARY PRECAUTIONS

Care during Operation.--Stopping the Engine 128

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

PRODUCER-GAS ENGINES

High Compression.--Cooling.--Premature Ignition.--The Governing of Engines 153

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

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

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

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

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

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. 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 . 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.

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:

Recent improvements made in suction gas-producers will probably lead to the wide introduction of producer gas engines even for small power.

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.

These various cycles succeed one another, passing through the same phases in the same order.

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.

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.

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 . 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.

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 . 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 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.

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.

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.

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

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 .

Among the parts of the piston which rapidly wear away because constant lubrication is difficult, is the connection with the piston-rod . 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.

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