Gasoline
engines have four strokes and six
processes in each cycle. During the
intake stroke, air and fuel are drawn into the cylinder; the volume and
potential energy increase. Next, the
compression stroke adiabatically compresses the gases; the volume
decreases and
the temperature increases. The spark
does not occur during a stroke but when the piston is fully raised,
this causes
the gases to ignite keeping relatively the same volume.
In the power stroke, the gas adiabatically
expands; the temperature decreases and the volume increases. Finally, the exhaust valve is opened so in
the exhaust stroke when the piston moves up the gasses are released
causing the
volume to decrease.
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