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Name: Robert
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Age: 15
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How do Diesel engines work?

Diesel engines are very similar to gasoline engines, except that they don't have spark plugs. In both diesel and gasoline engines, a fuel/air mixture is added to the cylinder when the piston is pulled back, and then the flywheel drives the piston forward, compressing the fuel/air mixture in the cylinder. This fast compression causes heating in the mixture. In a diesel engine, this heating is sufficient to actually ignite the fuel mixture, and the hot gases produced force the piston back, which drives the flywheel. In a gaoling engine, the compression of the cylinder is not suficient to ignite the fuel/air mixture, and a spark is used to do the job.

Richard Barrans Jr., Ph.D.

I noticed that you listed the operation of the diesel engine as compressing the fuel/air mixture....when in fact the air is compressed and then the fuel is injected into the cylinder. It is the heat of the air compression and the atomization of the fuel that results in the ignition. Without this there would be no way to control the timing of the burn. The gas engine uses spark to ignite the fuel at a specific timing window while diesel is timing the injection point. This was for years controlled through mechanical effort but today is controlled with fully authorized onboard computers.

Dwight Massey
Diesel Technology
Linn State Technical College

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