engines_notes_for four stroke engine.ppt

4strokes

1. Engine
Fundamentals

2. •The engine is the source of power for the
vehicle.
•It converts energy stored in fuel, into
motion.

3. Engine Operation
•Fuel is burned inside the engine’s
combustion chamber to produce heat.
•Heat causes expansion of gases in the
engine.
•Expansion in the combustion chamber
produces pressure.
•Engine components convert pressure
into rotating motion.

4. Engine Operation

5. Piston Travel
(TDC, BDC)
•Top dead center (TDC)
–piston is at its highest point
in the cylinder
•Bottom dead center (BDC)
–piston is at its lowest point
in the cylinder
•Piston stroke
–distance the piston slides up
or down from TDC to BDC

6. Four-Stroke Cycle
•Requires four piston strokes to complete
one cycle.
•Every four strokes, the engine produces
one power stroke.
•Two complete crankshaft rotations are
required to complete the four-stroke-cycle.
•Almost all automobiles use four-stroke-
cycle engines.

7. Intake Stroke
•Draws fuel and air into the
engine.
•Intake valve is open.
•Exhaust valve is closed.
•Piston slides down and forms a
low pressure area in the cylinder.
•Atmospheric pressure pushes the
air-fuel mixture into the engine.

8. Compression Stroke
•Compresses the air-fuel
mixture, making it more
combustible.
•Piston slides upward.
•Both valves are closed.

9. Power Stroke
•Burns the air-fuel mixture and
pushes the piston down with
tremendous force.
•Both valves are closed.
•Spark plug fires, igniting the air-
fuel mixture.
•Pressure forms on the top of
the piston.
•Piston is forced down, rotating
the crankshaft.

10. Exhaust Stroke
•Removes the burned gases
from the cylinder.
•Piston moves upward.
•Intake valve is closed.
•Exhaust valve is open.
•Burned gases are pushed
out the exhaust port.

11. Four-Stroke Cycle