Home > Encyclopedia of Science > Internal-Combustion Engine

• Basic principles
• Development of the internal-combustion engine

The invention and development of the internal-combustion engine in the nineteenth century has had a profound impact on human life. The internal-combustion engine offers a relatively small, lightweight source for the amount of power it produces. Harnessing that power has made possible practical machines ranging from the smallest model airplane to the largest truck. Lawnmowers, chainsaws, and electric generators also may use internal-combustion engines. An important device based on the internal-combustion engine is the automobile.

In all internal-combustion engines, however, the basic principles remain the same. Fuel is ignited in a cylinder, or chamber. Inside the sealed, hollow cylinder is a piston (a solid cylinder) that is free to move up and down and is...