Part 1 of Essay
An internal-combustion engine is a heat engine that burns fuel and air inside a combustion chamber located within the engine proper. Simply stated, a heat engine is an engine that converts heat energy to mechanical energy. The internal- combustion engine should be distinguished from the external- combustion engine, for e ....

Part 2 of Essay
.... In the former, a spark ignites a combustible mixture of air and fuel; in the latter, high compression raises the temperature of the air in the chamber and ignites the injected fuel without a spark. The diesel engine is a compression-ignition engine. This article emphasizes the spark-ignition engine. The invention and early development of internal-combustion engines are usually credited to three Germans. Nikolaus Otto patented and built (1876) the first such engine; Karl Benz built the first automobile t ....