CRANKCASE
COMPRESSION
CCC
(Two Stroke
Engines)
A crankcase is the housing for the crankshaft in IC engine.
In most modern engines, the crankcase is integrated into the engine block.
Refer the following link:
Many
2 stroke engines use a crankcase-compression design, where a partial
vacuum (suction) draws the air-fuel
mixture into the Spark Ignition (SI) engine (or) air into the Compression
Ignition/Injection (CI) engine as the piston moves upwards.
Then as the piston
travels downward, the inlet port is uncovered and the compressed air-fuel mixture
(or) air in SI (or) CI engine respectively is pushed from the crankcase (bottom
side) into the combustion chamber (top side).
Crankcase-compression designs are often used in small petrol (gasoline) engines for motorcycles.
This design
has also been used in some small diesel
engines, however it is less
common.
Both sides of the piston are used as working surfaces.
The
upper side is the power piston, the lower side acts as a pump. Therefore an
inlet valve is not required. Unlike other types of engines, there is
no supply of oil to the crankcase, because it handles the fuel/air mixture.
Instead two stroke oil is mixed with the fuel used by the engine and
burned in the combustion chamber.
Crankcase compression ratio can be determined by cylinder capacity (cylinder volume) and crankcase volume [the piston is at top dead center position].
Composed By:
E-Mail:
R.Satheesh, M.E., Asso Prof., rsatheeshemail@gmail.com.
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