INTERNAL COMBITSTION EN GINE, a type of prime 'mover in which the actuating energy, in the form of heat, is generated by combustion within the cylinder of the engine.
The commercial introduction and lin provements of the internal combustion engine have been comparatively recent, as it was only in 1878 that Otto placed the first important commercial gas en gines upon the market. In his engine, as in the common motor of to-day, the gas was compressed before it was ig nited.
The two great classes into which in ternal combustion engines may be di vided are: done at approximately the end of the compression; fourth, the expansion of the gas, resulting from combustion; which forces the piston down; and fifth and last, forcing out the burnt gases on the up stroke of the piston. This type of motor, which requires four strokes of the piston to complete its cycle, is known as a four-cycle motor, while some motors with special valve arrangements and A. Those in which the ignition of the fuel occurs at constant volume.
B. Those in which the ignition of the fuel occurs at constant pressure.
The common gasoline motor of to day is of the first type, and usually op erates under what is known as the Otto cycle: first, charging the cylinder with fuel, which is done on a down stroke of the piston; second, the compression of the fuel on the up stroke of the piston; third, the ignition of the fuel, which is deflectors go through a complete cycle in two strokes.
Gasoline is the common fuel of this type of motor, although there are models designed to operate on natural gas, al cohol, and kerosene. The fuel is mixed with air in a carburetor or similar de vice. The entrance of the fuel into the cylinder, as well as the expulsion of burnt gases, is controlled by valves, which may be of the poppet and cam type, or of the sleeve variety. In a modern motor the fuel is ignited by an electric spark, properly thned, which is usually furnished by a storage battery and intensified by a coil, or generated by a magneto. The lubricating system is usually either of the force feed or the splash type, and a great majority of the engines are water jacketed for cooling. This type of motor is used for motor vehicles of aIl types, for small power plants, airplanes, and motor boats.
The typical internal combustion engine of the second type is the Diesel Engine, invented by a German, Rudolf Diesel, in 1898. In the Diesel Engine air is drawn into the cylinder, compressed to about economy is possible with this type of motor.