Internal-combustion engine in which air is compressed to a temperature sufficiently high to ignite fuel injected into the cylinder, where combustion and expansion activate a piston (see piston and cylinder). It converts the chemical energy stored in the fuel into mechanical energy, which can be used to power large trucks, locomotives, ships, small electric-power generators, and some automobiles. The diesel engine differs from other internal-combustion engines (such as gasoline engines) in that it has no ignition system and so is often called a compression-ignition engine. Diesel fuel is low-grade and comparatively unrefined. Compared to other internal-combustion engines, diesel engines are more reliable, last longer, and cost less to operate, but they also produce more air pollution, noise, and vibration.
This entry comes from Encyclopædia Britannica Concise.
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