Precombustion Engine

an internal combustion engine in which carburetion is improved by means of a precombustion chamber. The fuel, or working mixture, is first fed into the precombustion chamber, where it is partially burned. When the fuel vapors are ignited, the pressure in the chamber increases, as a result of which the mixture of heated fuel and combustion products enters the combustion chamber above the piston. The steady rate of combustion of the fuel as it is expelled from the precombustion chamber into the combustion chamber provides for a uniform increase in the pressure in the cylinder, which results in the smoother operation of the precombustion engine.

A diesel’s precombustion engine operates steadily, without smoking, over a wide range of rotational speeds, and its injection pressure is lower than that of other diesel types. An important advantage of such engines is that they can use any grade of fuel. A disadvantage is the difficulty in starting because self-ignition requires thorough preheating of the precombustion chamber. To facilitate starting, electric glow plugs are used to preheat the air in the precombustion chamber.

For gasoline precombustion engines, the fuel consumption is 6 to 8 percent lower by weight, and there are fewer toxic exhausts. However, stability and reliability of performance are diminished under some modes of operation.