2&4 stroke engine cycles
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Transcript of 2&4 stroke engine cycles
Dr. Walid Abdelghaffar
Intake Stroke
Intake valve opens,
admitting fuel and air.
Exhaust valve closed
for most of stroke
Compression Stroke
Both valves closed,
Fuel/air mixture is
compressed by rising
piston. Spark ignites
mixture near end of
stroke.
Intake
Manifold
Spark
Plug Cylinder
Piston
Connecting
Rod Crank
Power Stroke
Fuel-air mixture burns,
increasing temperature
and pressure, expansion
of combustion gases
drives piston down. Both
valves closed - exhaust
valve opens near end
of stroke
1 2 3 4
Exhaust Stroke
Exhaust valve open,
exhaust products are
displaced from cylinder.
Intake valve opens
near end of stroke.
Crankcase
Exhaust
Manifold
Exhaust Valve Intake Valve
Dr. Walid Abdelghaffar
Dr. Walid Abdelghaffar
Dr. Walid Abdelghaffar
Power Stroke
Dr. Walid Abdelghaffar
Dr. Walid Abdelghaffar
Compression
(ports closed)
Air Taken Into
Crankcase
Combustion
(ports closed) Exhaust
(intake port closed)
Air compressed in crankcase
Scavenging
and Intake
(ports open)
Dr. Walid Abdelghaffar
Mechanical Cycle
v
p
1
2
3
4
TDC BDC
v
p End of combustion
TDC BDC
Ignition
Exhaust
valve
opens
Intake
Inlet
valve
opens
Thermodynamic Cycle The Otto Cycle
pat
m
Dr. Walid Abdelghaffar
Dr. Walid Abdelghaffar
Dr. Walid Abdelghaffar
4stroke air standard OTTO cycle, 6-6a-1-2-3-4-5-6, for SI
engine operating at part load
• W6-1 = Pi(V1-V6) = PiVd
• W5-6 = Pext(V6-V5) = PexVd
• (Wpum)net = (Pi- Pext) Vd
• Pmep= (Wpump)net/Vd
• = (Pi - Pext)
Dr. Walid Abdelghaffar
Ref. Internal combustion engines and air pollution, E. F. Obert