ENGINES, GAS AN!) OIL. Gas-engines are now commonly used with a producer gas, made on a continuous process by air and steam being passed through incandescent coal. From the generator it is taken to the scrubber for the purpose of cleaning and cooling, and it is thence allowed to enter a small holder. From this the gas-engine draws its supply, and in case the pro duction of gas exceeds the consumption, the holder filling and moving to its upper position will strike a stop, by which supply of steam and air is cut off from the generator, and the making of gas sus pended until the drop of the holder causes it to be resumed again. In a test made by Prof. K. Teich mann, of Stuttgart, of a twin-cylinder Otto engine worked with producer the engine developed a brake-power of about 52 horse-power, and the total fuel consmnption, including that used for the superheating boiler, was 1.6 lb. per brake, or barely 1.3 lb. per indicated horse-power per hour.
A still better result is reported in English tests—in ltobinson's Gas and Petroleum En gines"—which says that tests with an Otto engine, using I)owson gas, and indicating about 32 horse-power, have shown that the total fuel consumption, including that used for the production of superheated steam in the gas producer and for getting up fires at starting of the Dowson generator, was 1-2 lb. per indicated horse-power per hour. With a large twin-engine of 100 horse power only 1-1 lb. of coal was required. The Otto guts-engine is fully described on p. 032, vol. i, of this work. It is represented in its most recent forms—horizontal and vertical—in Figs. 1 and 2.
The Rollasom Gas-Eagine, made by the Electric Manufacturing and Gas-Engine Co., Greenbush, N. V., is of the three-cycle type—i. the crank-sltaft makes three revolutions for each explosion of gas, and the governor acts to regulate the amount of gas supplied for each explosion, front the maximum down to a point at which it can no longer he used economically, when the supply is cut off entirely, and no explosion takes place until a sufficient diminution of speed occurs.
The operation of the engine is its follows: Supposing an explosion to have just taken place, the piston, under the impetus given, makes a for ward stroke; the exhaust-valve is then opened and the piston returns.
expelling the lamer portion of the products of combustion. During the next forward strokea scavenger charge of air is drawn into the cylinder, and on return stroke is forced out through the exhaust. thus entirely clearing the cylinder and explosion chamber. On the fifth stroke a combustible charge of gas and air is drawn in, compressed ready for ignition by the sixth or return stroke; Ihus the cycle is completed. At the com mencement of the seventh stroke an explosion again takes place, and so on. The construction of this engine is shown in Figs. 3 and 4. The connecting-rod is pivoted directly to the piston,
which has a guiding trunk. The cylinder is sur rounded with a venter jacket, which extends around the eombustion-chamber up to the rear valve-face. The chamber itself is isolated from the influence of the jacket by alt annular space. which is filled with a non-conductor. A side-shaft, revolving at one third the rate of the crank-shaft, works the slide-valve at the back of the cylinder by means of a connecting,-rod and a rocking-beam. The slide-valve is shown in the horizontal section of the cylinder (Fig. 3), and is formed with ports through which the supply of air nod gas is ad mitted. The guts-valve is raised at the proper in stant by a cam, which is shaped to proport t he influx of gas to the sliced of the piston. The amount of gas admitted is regnhited by the gov ernor, which is driven by the side-shaft. The governor is connected by a rod to the valve. as it rises it t hi-oft les the supply of guts to make it correspond to t he work to he done. When I he dilution of the charge has been carried as far as is eci the guts is cat off entirely. A semmul lever connected with the governor carries a counter-weight, and by altering I he position of this weight the speed of the engine can be varied. This lever can lw readily put ita or out of eonnect ion with Ilie governor. its principal object being to enable the engine to be slowed down when not nail:111v doing work. When combustible mixture is to be admitted In the cylinder, the valve-ports coincide with admission. gas, and air inlets. the gas-valve is opened and the champ flows in, following the outward movement of the piston. The first portion of the combustible gases taken in flows down the -- center of the cylinder until the piston stops, and then it divides and flows back along the walls. This portion, which is diluted with the air in the combustion-chamber, is congregated round the tiring-port, while the richer part of the charge is situated next the piston. The weaker part is ignited first, and the velocity of combustion increases as it approaches the richer part. Prof. A. B. W. Kennedy, of London, made in 1888 a test of this engine under varying conditions, and his report of its performance is published in Engineering, May 4th and 11th of that year. The results as to its efficiency are summed up as follows, being the average of four experiments: Percentage of whole heat of combustion turned into work 19.6 Percentage rejected in jacket water... ........ ................ 33 Percentage rejected in exhaust 43.1 Percentage rejected in blank charge and unaccounted for 4.3 The mechanical efficiency of the engine on net indicated horse-power during the trials ranged from 861 to and the consumption of gas per indicated horse-power her hour ft. to 21.68 ft.