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.
Linn State Technical College
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Update: June 2012