The fact has already been briefly noted that not a few of the gas engines now on the market are adapted as well to the use of gasoline as to the use of gas proper, and that only a few slight modifications of design are sometimes necessary, and are provided for to permit changing from one fluid to the other.
/fig. 13.jpg) Fig. 13— The Caldwell-Charter Gas Engine |
/fig. 14.jpg) Fig. 14— The Caldwell-Charter Gas Engine, Sectional View |
Such provision is made in the case of the Otto engine, as described in the preceding paper, and also in that of the Caldwell-Charter gas engine, built by the
H. W. Caldwell & Son Company, Chicago, Ill., and shown in perspective and in sectional elevation, respectively, in Figs. 13 and 14. In both these views the engine is represented as arranged for the use of gasoline. In Fig. 14,
A is the working cylinder;
B, the piston;
C, the inlet valve to the cylinder;
D, the mixing chamber;
E, a gasoline pump;
E, an air-gate worked by the rod
J, which, in turn, is operated by the governor;
K, a gasoline supply regulating valve;
H, a gasoline tank;
NN, pipe from gasoline pump to a brass pan or reservoir,
P;
0, a supply pipe from gasoline tank to pump;
Q, the ignition tube; and
R, the chimney surrounding it;
I and
L are air suction pipes taking their air supply from the hollow base of the engine.
The pump
E works constantly and keeps the gasoline in the small brass pan,
P, which holds about a quarter pint, at a level fixed by an overflow pipe, which returns the surplus to the supply tank. The air-gate
F is a brass plate, having two holes so arranged that in normal position a free passage of air is allowed through pipe
I. When the governor opens the air-gate, the pipe
I is closed and the air is sucked through pipe
L. In this pipe is a nozzle leading to the pan
P, and the passing air draws from nozzle the proper amount of gasoline and forms a combustible mixture of gasoline and air. Each suction takes fresh gasoline from the reservoir, always the same quantity as controlled by supply or throttle-valve
K, and the charges of gas are therefore of equal strength and value. The ignition tube
Q is kept at a uniform heat by a simple gasoline burner, furnished with engine. This tube is surrounded by the asbestos lined chimney
R, which retains the heat. The governor is arranged on the crank-shaft; and through the rod
J operates the air-gate
F as already intimated. The exhaust valve, shown at the side of the cylinder, is controlled by a spring and a rod, receiving motion from the larger of two gear wheels. This gear wheel, as will be understood, is twice as large as the smaller driving pinion on the main shaft, and, therefore, makes only half as many revolutions as the latter, thus, of course, opening the exhaust valve only once in every two revolutions of the shaft. The engine, it would seem almost unnecessary to state, works on the Otto cycle. A water jacket, as usual, surrounds the cylinder. The engine, when intended for the use of gas instead of gasoline, dispenses with the gasoline pump and tank, and one of the suction pipes is connected with a gas supply pipe, in which a gas valve is located. It will be seen, therefore, that at a slight expense the gasoline engine can be changed to a gas engine, or vice versa.
A 95 indicated horse-power Caldwell-Charter gasoline engine, developing 65 actual horse-power, is now furnishing power for a large grain elevator at Camden, N. J., and is said to give entire satisfaction. For such large engines the makers supply a self-starter, consisting of a hand pump for forcing a charge into the cylinder, and a detonator for exploding the charge after it has been introduced. This gives the engine its first impulse, after which it continues to operate with its automatic gear.
/fig. 15.jpg) Fig. 15— The Roots Gas Engine |
/fig. 16.jpg) Fig. 16— The Roots Gas Engine, Sectional Elevation |
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The Roots engine is built by the
Roots Economic Gas Engine Company, London. It works on the Otto cycle, there being one explosion for every two revolutions, but the compression of the gas and air mixture is effected in a novel manner, which constitutes the chief feature of the engine. Figs. 15 and 16 represent a perspective view and sectional elevation respectively. The admission valve, shown on the left of Fig. 16, opens into a special compression chamber. No special gas valve is used, the supply being adjusted by suitably proportioning the gas inlet. To make the manner of working clear, we will assume that one working cycle has just been completed. By studying the sectional view it will then be understood that on the next upward stroke of the piston, or on the suction stroke, the air and gas are drawn in through the admission or suction valve, which opens automatically, and displace whatever products of combustion may be in the compression chamber. The latter is thus filled with a rich mixture of gas and air, only a small proportion of which enters the working cylinder through the port a. This cy1inder, therefore, at the beginning of the first down-stroke, contains a rather dilute mixture of fresh gas, air, and burnt gases, which, as well as the rich charge in the compression chamber, is compressed when the piston descends. Before the piston has gone down very far, however, it passes over the port a, cutting off communication with the compression chamber, and during the remainder of the stroke only the dilute mixture in the cylinder is further compressed. At the end of the stroke this mixture is fired by a tube igniter shown at the right. The pressure rapidly rises and the piston commences its working stroke. After having gone a short distance it uncovers the port a leading to the compression chamber, and the rich charge there is further compressed under the influence of the explosion of the weak charge, and is fired.
/fig. 17.jpg) Fig. 17— The Roots Gas Engine, Indicator Card |
Just how this manner of working affects the diagram is shown in Fig. 17, which is a sample indicator card. After the first explosion, it is seen, the pressure begins to fall, and when the port an to the compression chamber containing gas at a low pressure begins to open, this fall is accentuated, but very soon the fresh charge in the chamber is fired, and the pressure line rises again, and is well maintained for a considerable proportion of the stroke. At the end of the working stroke the exhaust valve is opened by the action of an eccentric.
The peculiar system of compression is claimed by the makers to effect a considerable economy of working. The degree of compression in the special chamber amounting to about 120 pounds per square inch. This is considerably more than is ordinarily attained in gas engine compression.
/fig. 18.jpg) Fig. 18— The Palatine Gas Engine,, Vertical Section |
| /fig. 19.jpg) Fig. 19— The Palatine Gas Engine, Front Sectional Elevation |
| /fig. 20.jpg) Fig. 20— The Palatine Gas Engine, Side Elevation |
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A novel form of gas engine built by the
Palatine Engineering Company of Liverpool, England, is shown in Figs. 18, 19 and 20, which represent vertical sections and an elevation. The engine is of the vertical type, and the crank and connecting rod are completely cased in. An air inlet valve admits air into the enclosed space when the piston descends. This air is slightly compressed on the up-stroke, and when the piston reaches the top of the stroke, a quantity of this compressed air rushes into the cylinder through air blow—through ports, the cylindrical part of the piston being then above these ports—see Figs. 18 and 19. At this moment the exhaust valve is opened by the lever
L, Fig. 20, which is operated by one of the cams on the spindle driven by the wheel
W. The Cylinder is thus completely swept out by a charge of fresh air. Referring to Fig. 18 it will be seen that the air suction valve is placed in the space below the cylinder and close to the gas admission. The gas is taken into the gas pump, Figs. 19 and 20, and the quantity admitted is determined by the governor and detent. Fig. 19, which control the admission of the gas to the pump by means of the small gas valve.
Ignition of the charge is effected by a tube igniter,
I T, and the moment at which the charge is permitted to enter the tube is controlled by a valve
I V; worked by the lever
L, Fig. 20. The engine, it will be noted, works on the Otto cycle.
/fig. 21.jpg) Fig. 21— The Campbell Gas Engine |
The Campbell engine made by the
Campbell Gas Engine Company, London, shown in Fig. 21, is designed to work according to a cycle in which there is an explosion at each revolution, twice as many, therefore, as in an engine working on the Otto cycle.
This effect is attained by taking in the charge of gas and air by means of a pump, instead of by the action of the main piston. This pump is driven off a crank-pin in the side of the flywheel, and draws in gas and air through ports, controlled by a slide valve. There is a straight connection between the pump and the working cylinder, interrupted only by a simple non-return valve. The compressing action of the pump on the back stroke is so timed that the mixture attains a pressure of from six to ten pounds, just as the main piston passes an exhaust port in the side of the cylinder, and allows the expanded, acting charge to escape. The new charge then lifts the valve and enters the cylinder, driving the remaining products of combustion before it through the exhaust valve. On the return stroke of the main piston the charge is compressed, and at the commencement of the next stroke, it is fired by a tube igniter.
/fig. 22.jpg) Fig. 22— The Campbell Gas Engine, Governor Detail |
The slide valve by which the admission of gas and air to the pump is controlled, is driven in one direction by an eccentric and in the opposite direction by a spring. The connection with the eccentric is not positive, but between the eccentric rod and the valve is interposed a hit-and-miss motion under the control of a governor. When the speed of the engine becomes too high, the governor raises the hit-and-miss device, and the valve is either not opened at all, or is opened only slightly, depending upon the position of the stepped piece, shown in Fig. 22. When the engine is permanently on light work, the amount of the gas and air charge can be reduced by setting the eccentric further around, and the strength of the charge can be graduated by means of a cock on the inlet pipe.
/fig. 23.jpg) Fig. 23— The Campbell Gas Engine, Indicator Cards |
The several indicator cards, Fig. 23, clearly show the effect of igniting gas mixtures of varying quantity in the engine. So far as structural features are concerned, it will be noticed from the perspective view of the engine that the cylinder does not overhang, as in most gas engines, and the cylinder jacket, engine bed and crank bearings are all cast together in one solid piece.
/fig. 24.jpg) Fig. 24— The Foos Gas Engine |
In the Foos engine, either gas or gasoline may be used indiscriminately, the design being the same in both cases, the use of gasoline, however, of course necessitating the addition of a gasoline tank or carburetor to the outfit as shown in the general view, Fig 24. The engine is designed to work on the Otto cycle, there being ordinarily one explosion in the cylinder at every second revolution, or fourth stroke.
We will assume, by way of explanation, that the piston is making the first stroke of a cycle, or that, in other words, it is descending and sucking in the explosive charge. The gas then goes to the engine through the valve
O, and mixes with air coming through the branch pipe and valve
N. The gas and air mixture passes on through the governor valve
M ascends in the vertical pipe shown at the left of the engine, passes through the check valve
P, and enters the exploding chamber
B through a lift valve, which ordinarily is kept down on its seat by a spring,
C, but which opens automatically under the influence of the partial vacuum formed in the engine cylinder during the suction stroke. When gasoline is used instead of gas, air is drawn through the gasoline tank or carburetor, entering at
U, and in its passage it absorbs sufficient gasoline vapor to make it ignitable. Warm air is used to absorb the gasoline, being led to the tank pipe
U through the rubber hose shown in dotted lines. This hose is connected to a small drum,
J on the exhaust pipe
A. The drum is perforated so as to admit air which, in passing around the exhaust pipe is warmed. The gasoline vapor coming from the carburetor passes through the check valve at
R, at the outlet end of the tank, and then on to the engine as just described. The engine cylinder and chamber
B having been filled with the explosive mixture, the piston performs its upward or compressing stroke, during which the charge is compressed. At the beginning of the next down-stroke ignition of the charge is effected in the exploding chamber
B by an electric spark, caused by the contact and immediately following separation of the inner ends of the two electrodes,
D and
E.
/fig. 25.jpg) Fig. 25— The Foos Gas Engine, Igniting Electrodes |
The arrangement of these will be better understood from Fig. 25. When the two ends
X and
Y are brought together, as shown in this illustration, the electric current from the battery provided with the engine is closed, and when they are then quickly separated, a spark is produced, and the gas or vapor charged is exploded.
The connection and separation of the points of the electrodes is caused by the revolving motion of electrode E, Fig. 24, the end of which is made in the shape of a half circle as shown at
X in Fig. 25, bringing the points
X and
Y together at every revolution of electrode
E. Electrode
D is made to screw further in so that when the inside end Y is worn off it can still be kept in contact with electrode
E at
X. Care must be taken not to screw it in so far but that there will be a separation of an eighth of an inch between the points of the two electrodes at every revolution of electrode
E. The latter is worked from the main shaft through the intervention of two gear wheels and the rod
f, the secondary gear wheel
K being twice the size of the one mounted on the driving shaft, and, hence, making only half as many revolutions. It follows, therefore, that the electrode end
X (Fig. 25), will revolve once for every two revolutions of the engine shaft, and, accordingly, will produce an igniting spark once for every two such revolutions.
The explosion having taken place the piston is forced down, making its working stroke, and on the next upstroke the products of combustion are expelled from the cylinder through the exhaust valve and pipe A at the back of the cylinder. The exhaust valve, which is of the lift type, is worked by a cam on the spindle of the gear wheel
K, and by a rock-shaft connection. This valve, which is fitted with a spring to bring it firmly back to its seat after having been opened, and the governor valve
M are the only valves in the engine which receive positive motion from the engine shaft.
The governor is of the centrifugal type, and is mounted on the crank shaft. Its revolving weights are shown at
L L. These, it will be noted, revolve in the same plane as the fly-wheel, and, when the normal speed is exceeded, fly outward and move a lever controlling the position of the valve
M, and cutting off or reducing the supply of explosive mixture.
The engine has the usual water jacket to prevent over-heating of the cylinder. In Fig. 24 the inlet and outlet pipes for this jacket are marked
H and
I, G is a stop-cock for the escape of compressed gas, and is to be opened when starting up:
T is an oil cup connection;
V is a float in the gasoline tank to indicate the level of the fluid,
W is the feed opening for tank.
The engine is built by the
Foos Gas Engine Company, of Springfield, Ohio, the range of sizes being from two to ten horse-power.
/fig. 26.jpg) Fig. 26— The American Priestman Petroleum Engine |
/fig. 27.jpg) Fig. 27— The English Priestman Petroleum Engine |
The Priestman oil engine is made both in the United States and England, Messrs.
Priestman & Co., of Philadelphia, the American builders, turning out the design shown in Fig. 26, while the English builders, Messrs.
Priestman Bros., of London and Hull, have for their latest type of engine the one illustrated in Fig 27. The engine uses for fuel common petroleum such as is burned in lamps, and the quality best suited to this purpose is just what is safest in common use, that is, the highest proof oil. A sprayed jet of this oil is first broken up by compressed portions is drawn through an automatic suction valve into the engine cylinder by the piston in its forward stroke. On the return stroke this change is compressed to about half its bulk, and on the next forward stroke it is ignited electrically producing the working pressure. At the end of this working stroke, as it may be called, an exhaust valve opens and permits escape of the products of combustion during the succeeding return stroke, thus completing one cycle which, it will be observed, is the same as in the Otto engine, and to which frequent reference has already been made as the Otto cycle. The oil is burned precisely as it would be burned in the wick of an oil lamp, and all the oil is so burned, except that in contact with the comparatively cool surfaces of the water-jacketed cylinder. Upon these cooler surfaces, the oil not burned is condensed and furnishes the means of lubrication. As in many other engines of this type, there is in the Priestman engine a space at the back end of the cylinder over which the piston does not sweep in its motion. This space, or compression chamber, bears a fixed proportional relation to the whole cubic contents of the cylinder, and acts as the furnace and boiler that is to operate the engine, being, in fact, the seat of power of the machine.
Fig. 27, as already remarked, shows the latest type of the English Priestman engine. This differs from the earlier English design in that the various working parts have been made more accessible, and at the same time have been somewhat simplified. As the illustration shows, the hand pump, being driven by a separate rod as formerly. The wide opening in the frame permits of the vaporizer and spray maker being got at in case of need with a minimum of trouble. In all other points the engine is similar to the old type, the action of which has already been outlined.
In the American design, shown in Fig. 26, the idea of making all the parts readily accessible has been still further carried out; hence, the immediately striking difference of appearance. All the main features of the engine are, however, practically the same. In the English engine, it will be noticed, the fly-wheel is placed outside of the bearings, and the shock from the sudden ignition of the charge thus comes upon the crank. With the principle adopted in the American design, it is argued that the two fly-wheels which are used instead of one, and which form part of the crank, offer their great weight to the blow between the bearings and present a mass of sufficient inertia to neutralize the effect of this blow.
/fig. 28.jpg) Fig. 28— The American Priestman Petroleum Engine, Explanatory Diagram |
The diagram shown in Fig. 28 more clearly explains the operation of the engine. In this illustration,
A represents an oil tank filled with any ordinary high test (usually 150 degrees test) oil, from which oil under air pressure is forced through a pipe to the three-way cock,
B, and is thence conveyed to the atomizer
C, where the oil is met by a current of air and broken up into atoms and sprayed into the mixer
D. It is there mixed with the proper proportion of supplementary air and sufficiently heated by the exhaust from the cylinder passing around this chamber. The mixture is then drawn by suction through the inlet valve I into the cylinder E where it is compressed by the piston and ignited by an electric spark passing between the points of the ignition plug
F. the current for the spark being supplied from an ordinary battery furnished with the engine. The governor
G controls the supply of oil and air proportionately to the work performed.
The burnt products are then discharged through the exhaust valve
H, which is actuated by a cam. The inlet valve
I is directly opposite the exhaust valve. The air pump
j is used to maintain a small pressure in the oil tank to form the spray.
K is the water jacket outlet.
The engine at the Philadelphia works is now made in four sizes, ranging from five to twenty indicated horse-power.
/fig. 29.jpg) Fig. 29— The English Priestman Double Cylinder Marine Engine |
/fig. 30.jpg) Fig. 30— The English Priestman Engine & Pump Combined |
One of the various applications of the Priestman engine has been made by the English builders to the propulsion of a launch which, last year, was running on the river Thames, where she aroused considerable interest. The boat was thirty-six feet long by seven feet three inches beam, by four feet six inches deep. A ten horse-power engine of the marine type, illustrated in Fig. 29, was used, there being two cylinders each nine inches in diameter by nine inches stroke. In principle the engine was the same as the regular Priestman oil engine, the oil being sprayed by a jet of compressed air and afterward heated in a vaporizer kept hot by the exhaust gases. The ignition also was effected electrically, a battery being used to give the spark. The valve gear in the engine, as shown, is very simple. The inlet valves on top of the cylinders act automatically.
The engine was placed amidships and occupied very little space as compared with machinery and boiler space of a steam launch. The speed of revolution was controlled by a governor, which cut off a part of the charge according to the amount of work to be done, and the engine was slowed down when required by depressing the governor spindle by hand. The normal speed was 240 revolutions per minute, giving the boat a speed of about nine miles an hour. In this marine type of engine the motion is in one direction only, and reversing is effected by means of a friction clutch which also admits of running the engine detached from the propeller. The boat was easily handled and the machinery required very little attention. About forty gallons of oil, sufficient for several days' running, were carried in the bow, from which the engines drew their supply.
/fig. 31.jpg) Fig. 31— TheKane Electro-Vapor Engine |
The Kane Electro-Vapor engine, like the one just described, is also adapted to the use of either gas or gasoline. It is built by Messrs.
Thomas Kane & Co., Chicago, Ill., and is shown in Fig. 31 as arranged for the use of gasoline. The engine works on the Otto cycle, there being one working stroke in every four. The gas or gasoline vapor goes to the engine through the regulating valve
G, and mixes with a suitable supply of air, which is drawn in from the hollow bed of the engine through the cock
B. The admission valve through which the mixture finally enters the exploding chamber is a poppet valve, operated by a lever on the other side of the engine, not visible in the illustration, and controlled by a centrifugal governor through a hit-and-miss device. Having passed through this admission valve during the first stroke of the cycle, the mixture is compressed during the second stroke, and exploded at the beginning of the third stroke, exhaust of the burnt gases, as usual in this class of engines, taking place during the fourth stroke. The exhaust valve chamber is marked
E, the valve itself also being a poppet valve ordinarily kept closed by the spring shown. It is opened at the proper exhaust moment, however, by being pushed upward by the end of a pivoted lever, which receives motion from the crank shaft
E through the intervention of a small and a large gear wheel, in much the same manner as that followed in connection with the Caldwell-Charter engine described in the beginning of this paper. The explosive charge is ignited by an electric spark, and one of the electric contact points, connected with one pole of a battery, is carried by the exhaust valve operating lever just mentioned. It is shown at
C and is pressed against another contact piece on the engine bed at the end of every down stroke of the right hand end of this valve lever. The other pole of the battery is connected by a wire with an insulated electrode in the exploding chamber at the end of the engine cylinder. The second electrode is in the shape of a metallic point carried by the piston. At the proper moment for exploding a charge, the contact pieces at
C are pressing against each other, and the electrode on the piston, which then is at the right hand end of its stroke, is just breaking contact with the insulated electrode in the exploding chamber. The result is that a spark is produced and the charge is exploded. The contact pieces at
C are for the purpose of completing the electric circuit only at the end of every fourth stroke. At other times they are separated as will be understood from the nature of the connection to the exhaust valve lever. The cylinder is water-jacketed, and the water on its way from the jacket passes around the exhaust valve chamber, cooling it also, and is led off through the pipe
O.
/fig. 32.jpg) Fig. 32— TheKane Electro-Vapor Engine, Carburetor Sectional View |
Fig. 32 represents a sectional view of the carburetor or gasoline tank used when the engine is working with gasoline. It is a small circular tank partly filled with gasoline and connected with the engine by a pipe. It may stand five feet, or, for that matter, fifty feet away from the engine. Upon starting the engine, a current of cool air is drawn through suction pipe
E, and passing around through the circular chamber
XXX, finally arrives at the gas box
D; from there it passes directly into the engine cylinder through the connecting pipe. During its passage through the carburetor, the air absorbs the requisite amount of vapor for the charge. The carburetor works automatically and requires no attention other than that necessary to keep it supplied with gasoline. When the engine works with gas, the carburetor, of course, is not needed, and the end of the gas intake pipe carrying the valve
G is then connected directly with a gas supply pipe carrying the customary gas-bag to give uniformity of pressure. The engine is made in seven sizes ranging from one half actual horse-power up to ten. One of the uses to which this engine when using gasoline is being extensively applied is the propulsion of small boats, and special modifications have, accordingly, been made by the builders to successfully meet the requirements in such cases.
/fig. 33.jpg) Fig. 33— The Kane Electro-Vapor Launch |
/fig. 34.jpg) Fig. 34— The Kane Electro-Vapor Launch, Plan Sections |
/fig. 35.jpg) Fig. 35— The Kane Electro-Vapor Launch |
Thus Fig. 35 gives a general view of one of the marine engine outfits. The engine, as there used, is fitted up with two fly-wheels and a reversing gear. The latter consists simply of a friction wheel with rubber rim so arranged that when thrown, by means of the lever shown, against the inner side of either one or the other fly-wheel, it will, together with the propeller shaft, revolve either to the right or left as the case may be, moving the boat either ahead or astern while the engine runs always one way, being itself not reversible. With the friction wheel in mid-position, it will be at a standstill. This arrangement provides a noiseless reversing gear and one, which will respond at a moment's notice. Fig. 34 represents a plan and sections of a launch fitted up with the engine, while Figs. 33 and 35 are general views.
Messrs.
Kane & Co. build also a vertical gas engine, and a special horizontal gas engine and pump combination designed for supplying water for hotels, residences, etc.
Information Sources
- Cassier's Magazine, V3, Apr 1893 pgs. 427-444