An ICE is an engine where fuel combustion 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 engine components. The force is typically used on pistons, turbine blades, or a nozzle.
This force moves the part over a distance, transforming chemical energy into sound mechanical energy. The first commercially successful internal combustion engine was created by Étienne Lenoir around 1859. and the first modern internal combustion engine was created in 1864 by Siegfried Marcus. The term internal combustion engine usually refers to an engine in which combustion is intermittent, such as the more familiar four-stroke and two-stroke piston engines, along with variants, such as the six-stroke piston engine and the Wankel rotary engine.
A second class of internal combustion engines uses continuous combustion: gas turbines, jet engines, and most rocket engines, each of which are internal combustion engines on the same principle as previously described.
Firearms are also a form of internal combustion engine. Internal combustion engines are quite different from external combustion engines, such as steam or Stirling engines, in which the energy is delivered to a working fluid not consisting of, mixed with, or contaminated by combustion products. Functional fluids can be air, hot water, pressurized water, or liquid sodium heated in a boiler.
ICEs are usually powered by energy-dense fuels such as gasoline, diesel, and liquids derived from fossil fuels. While there are many stationary applications, most ICEs are used in mobile applications and are the dominant power supply for cars, aircraft, and boats.
Typically an ICE is fed with fossil fuels like natural gas or petroleum products such as gasoline, diesel fuel, or fuel oil. There’s a growing usage of renewable fuels like biodiesel for compression ignition engines and bioethanol for spark ignition engines. Hydrogen is sometimes used and can be made from either fossil fuels or renewable energy.