An engine in which the combustion of a fuel, often a fossil fuel, occurs with an oxidizer, usually air, in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion apply direct force to some component of the engine. The force is applied to pistons, turbine blades, or a nozzle. This force moves the component over a distance, transforming chemical energy into useful mechanical energy.
Also known as Compression Ignition Engine.
See also Diesel Engine.