THE EFFICIENT GAS ENGINE For stationary work, where natural or artificial gas can be had, the gas engine is the most efficient kind of an internal combustion engine you can use. Not only is it the most efficient, but since there is a constant supply of fuel at hand and it can be used directly in the cylinder of the engine without any intervening apparatus it is safer and less trou blesome than an engine using liquid fuels.
Gas engines in all sizes from 1 to 150 horsepower are made with single cylinders, and from 150 to 1500 horsepower they are made with two cylinders, or twin cylinders, as they are called. Engines of from 1 to 8 horsepower have vertical cylinders, while they are made from 4 to 2000 horsepower with horizontal cylinders.
The Parts of a Gas Fangine.—In a gas engine of either the vertical or horizontal type there are eleven principal parts, and these are (1) the frame; (2) the cylinder; (3) the air valve; (4) the gas valve; (5) the exhaust valve; (6) the piston; (7) the connecting rod; (8) the crankshaft; (9) the eamsliaftl; (10) the igniter; and (11) the governor.
The is made of cast iron and on it rests the cylinder and crankshaft bearings. It must be heavy enough to prevent vibration and to keep the bearings from getting out of line. It is shown at A in Fig. 20.
Tice Cylinder and Water Jacket.—The cylinder (see B) has a water jacket C fitted around it so that water can be made to circulate between them. The cylinder has a ground bore, that is, it is ground out with an emery wheel instead of being bored out, and this permits the piston to fit much closer and of course this makes the compression better.
The Cylinder is also an iron casting and all of the valves are fitted in it and the igniter is mounted on it. The combustion of the fuel charge takes place in it and, hence, this part is called the combustion chamber. It is shown at D.
The Air, Gas and Exhaust Valves.—These valves are called poppet valves, and are kept closed by spiral springs. They have flat, steel heads with beveled edges so that they will seat, that is fit tight, into the inlet and exhaust ports of the cylinder.
The Air Inlet Valve.—The air and gas are taken into the cylinder through separate valves, when they mix inside of it to form the fuel mixture. The air valve is an automatic suction valve, that is, it is a valve that is opened by the suction of the piston at the same time that the gas inlet valve is opened, and it is kept closed during the other strokes by the spiral spring and the internal pressure on it. It is shown at E.
TAB Gas Valve.—This valve sets close to the air valve in the cylinder head, and it admits the gas into the cylinder at the same time the air is taken in by the suction stroke. It is opened at the right time by a cam working on the camshaft. All that is needed is to connect a gas pipe, with a gas cock in it, to regulate the supply of gas to the valve, and turn on the gas. It is the same as the air valve and is shown at F.
The Exhaust Valve.—As the burnt gases exhaust through this valve it gets very hot and it should therefore be water cooled. It is tined to open by and is worked from the camshaft by a cam and an exhaust lever. It is shown at G.
The Piston and Piston .Rings.—The piston is made of the same kind of iron as the cylinder and is accurately ground to fit it.
Different from a steam engine, the piston of a gas engine is long and hollow, with one end closed and the other open; again, instead of being packed with hemp or asbestos it has grooves cut in it and packing rings, or piston rings, as they are called, are slipped into them. These rings are also of iron and make the piston fit so closely to the cylinder, that the fuel mixture cannot leak by it.
The piston has a crosshead pin, called a wrist pin, set across its center and on this the small end of the connecting rod is secured. The piston and piston rings are illustrated at H and I, and the wrist pin at J. • The Connecting the piston is long no piston rod, guides and crosshead such as are used in a steam engine are required, hence the piston is usually coupled direct to the crankshaft with a con necting rod. How it is made is shown at K.