internal-combustion engine

CE5

Internal-combustion engines: In the four-stroke reciprocating engine (above), a mixture of fuel and air is taken into the chamber on the down-stroke of the piston, is compressed on the up-stroke, is ignited and provides power on the next down-stroke, and finally is exhausted on the up-stroke. In the Wankel rotary engine (below), the same sequence is accomplished in a continuous motion as the volume varies between the triangular rotor and the specially shaped chamber.

internal-combustion engine, one in which combustion of the fuel takes place in a confined space, producing expanding gases that are used directly to provide mechanical power. Such engines are classified as reciprocating or rotary, spark ignition or compression ignition, and two-stroke or four-stroke; the most familiar combination, used from automobiles to lawn mowers, is the reciprocating, spark-ignited, four-stroke gasoline engine. Other types of internal-combustion engines include the reaction engine (see jet propulsion, rocket), and the gas turbine. Engines are rated by their maximum horsepower, which is usually reached a little below the speed at which undue mechanical stresses are developed.

Sections in this article:

• Introduction
• Evolution of the Internal-Combustion Engine
• Environmental Considerations in Engine Design
• Cooling and Lubrication of Engines
• The Two-Stroke Cycle
• The Four-Stroke Cycle
• Rotary Engines
• Reciprocating Engines
• Bibliography

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