CI ENGINE
The
working of two stroke C.I engine slightly differ from the S.I engine. Instead
of spark plug, the fuel injector is placed on the top of the cylinder.
First stroke:
In
the first stroke, the piston moves from BDC to TDC. When the piston is at BDC, partially
compressed air from the crank enters into the cylinder through transfer port.
Then the piston moves upward and further compresses the air into high pressure
and temperature till the piston reaches TDC. At the end of the compression
stroke, the fuel injector the fuel in atomized form and ignited automatically
by the compressed air.
During
the upward movement of the piston, a slight vacuum will be produced at the
crank case to suck the air from the atmosphere.
Second stroke:
When
the fuel and air are ignited, it suddenly increases the pressure and
temperature of the gas. Therefore, the gases will expand and it pushes the
piston downward and producing the power stroke. During the expansion, some of
the heat energy produced is converted in to mechanical work.
During
the downward stroke of the piston, first it uncovers the exhaust port and the
burnt gases are sent out of the engine, at the same time, all the burnt gases
are not exhausted. Therefore, scavenging takes place in the cylinder.
At
the time of downward movement of the piston, already entered air in the
crankcase is partially compressed by the underside of the piston. This process
is called crank case compression.