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RISK ANALYSIS OF INTERNAL COMBUSTION ENGINE 35
VALVE PRODUCTION USING FMEA METHOD

travel of the piston along the cylinder, in either direction. [4][5]The four separate strokes are
termed:

Intake: This stroke of the piston begins at top dead center (T.D.C.) and ends at bottom dead
center (B.D.C.). In this stroke the intake valve must be in the open position while the piston
pulls an air-fuel mixture into the cylinder by producing vacuum pressure into the cylinder
through its downward motion.

Compression: This stroke begins at B.D.C, or just at the end of the suction stroke, and ends at
T.D.C. In this stroke the piston compresses the air-fuel mixture in preparation for ignition
during the power stroke (below). Both the intake and exhaust valves are closed during this
stage.

Power: This is the start of the second revolution of the four stroke cycle. At this point the
crankshaft has completed a full 360 degree revolution. While the piston is at T.D.C. (the end of
the compression stroke) the compressed air-fuel mixture is ignited by a spark plug (in a gasoline
engine) or by heat generated by high compression (diesel engines), forcefully returning the
piston to B.D.C. This stroke produces mechanical work from the engine to turn the crankshaft.

Exhaust: During the exhaust stroke, the piston once again returns from B.D.C. to T.D.C. while
the exhaust valve is open. This action expels the spent air-fuel mixture through the exhaust
valve.

Figure 2. Strokes and positions

Sayı 5, 2016 GiDB|DERGi