SINGLE-CYLINDER ENGINES
4·STROKE
DIESEL
ENGINE
PRINCIPLES
69
B
As the piston travels downward, the exhaust
valve closes and the intake valve opens,
allowing air to be drawn
into
the cylinder. When
the piston reaches the bottom of its travel
(SOC), the intake valve closes and remains
closed
for
the next 1 1/2 revolutions of the
crankshaft.
When the crankshaft continues to rotate, the
piston moves upward, compressing the air.
c
Injector
~i~~~~Exhaust
valve
o
As the piston almost reaches the top of
its
travel, the injector sprays fuel
into
the
combustion chamber. The fuel Is ignited by the
heat of compression. The piston continues to
top
dead center(TOC)and is pushed downward
by the expanding gases.
When the piston almost reaches SOC, the
exhaust valve opens and remains open until the
piston Is near TOC. The upward travel of the
piston forces the exhaust gases
out
of the
cylinder. After the piston has reached TOC,the
exhaust valve closes and the cycle repeats.
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