Gas-Engines and Producer-Gas Plants

, of the four-cycle type, such as are industrial

the manner in which the engine operates. A complete cycle comprises four dist

, creating a vacuum in the cylinder, and simultaneously

irst cycl

al position. All admission and exhaust valves are closed (Fig.

of its return stroke, the compressed mixture is ignited. Explosion takes place

ond cycle:

ycle: Explosion

second time. The exhaust-valve is opened, and t

urth cycle

ne another, passing through th

es of explosion-engines than were the old slide-valves used when the Otto engine was first introduced. The slide-val

rated 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. T

dern valve

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 quic

ndispensable that the valves should be readily accessible. Indeed, the valves should be regularly exa

olling mechan

uld, 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 v

ater-jack

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 ind

electric spark have taken the place of the obsolete naked flame. The last-ment

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

rolled 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 tempera

.-Valveles

ly 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

nition-tube

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 e

battery and spark-coil, or by means of a small magneto ma

ignition by spar

3.-Spa

efully 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

neto ignitio

and details of a magne

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,

acts of a mag

r regulating the m

c magneto-igniter applied to the cylinder-head of a Winterthur motor, and also a sectional view of the

les of which the armature rotates. At its conically turned end

thur electric i

D, made of bronze, is movable, and is fitted with a small interior contact-hammer, a percussion-lever, and an exterior recoil-spring

coils contained in a brass casing, and ac

pring and mounted on an eccentric spindle, the position of which can be varied by means of a regulating-lever (I).

cts of the Win

d spark on breaking the circuit. The marks on the armature should be noted. The position of the armature may be experimen

e at which the breaking of the circuit is effected can be regulated by shifting the handle (I). In starting the eng

evice 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

t 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 o

vice by which the ignition can be duly t

esign of t

face of the piston should preferably be plane. Curved surfaces are not to be recommended because they cool off badly. Likewise, faces having e

ton with lub

hus 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 e

ed at the rear of the piston. It is to be observed that makers of good e

ssage 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 o

ieces 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 fr

and liner of cylinde

r with independe

th 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 ver

ingle-acti

ne with incli

ttle 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

ne with strai

with correctly d

hat a maximum explosive pressure of 405 to 425 pounds per square inch will not s

royed 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 tru

y-wheel engine wit

pose 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 variation

rmits a more ready access

ird bearing, thus avoiding the overha

topping, and changing the load, the peripheral resistance varying in one of the fly-wheels,

ng ends of the shaft, will be so affected at the

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-

urved spok

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

Forged cr

ferred the cranks of which are not forged on (Fig. 30), but cut out of the mass of metal; furtherm

ect design of

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

-shaft with ba

be made of good steel, case-hardened to a depth of at least .08 of an inch. Their hardness and the degre

e adjustable to take up the wear. They are usually

engines may be considered fr

-Inertia

re 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 resi

nce 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 permiss

the ball or centrifugal governor controlling an admission-valve of the "hit-and-miss" type (Fig

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 engi

delicate mechanism from strains and stresses that are likely to destroy its sen

it-and-miss

to permit the manual variation of the

antity 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 ga

it-and-miss" type are either "ine

fugal type. They are generally applied only to industrial engines of sm

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 gover

stened (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.

within the limits of 2 to 3 per cent. between no load and approximately full load. Under equivalent condition

iable admiss

ssion system adopted. And the admission system varies essentially with th

-Vertica

an engine of the vertic

rica 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 wit

evations of a vertical o

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

the motive agent on the piston. The work performed is measured on an indicator card, by means of whi

"indicated" horse-power, less the energy absorbed by

ed to the power actually developed at the shaft. T

s, is reduced to a minimum, the "effective" horse-power is about 80 to 87 per cent. of the "indicated" horse-power, w

The manufacturers themselves do not seem to agree on its absolute value. A "nominal" horse-power, however, is equal to anyth

ons. 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 e

ss 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 e

rude 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, moreov

e 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

nder a mixture of air and gas, ignited at the proper time by allowing it to c

olently, 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 l

d by the compressed-air system, which is simpler

ufficient 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

-Tangye

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 t

connected with the reservoir is necessarily independent of the pipe by means of which the motor is starte

ank inclination of 10 to 20 degrees in the direction of the piston's movem

ng the rese

p-cock, which is closed again when the impulse is given and reopened at the corresponding period of the fo

d finally closing the two valv

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