Small Engines . ppt

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SMALL ENGINES
ENGINE
OPERATION FOR
A FOUR STROKE
ENGINE
SMALL ENGINES

An engine is a device which
converts energy into mechanical
motion to do work.

Small engines are described as
internal combustion engines rated up to
25 horsepower.

A small engine has either a
spark ignition or a compression ignition
based on how the fuel is ignited.

Small engines are classified as either
four-stroke cycle engines or two-stroke
cycle engines.
PARTS OF THE ENGINE
CYLINDER BLOCK
Engine component which
consists of the cylinder bore,
cooling fins, and valve train
components.
CYLINDER
HEADMade of cast
aluminum alloy that are
Engine component made out of
lightweight and dissipate heat
cast aluminum alloy fastened
rapidly.
to the end
of the cylinder block
COOLING
FINS
farthest
fromthin
the cast
crankshaft.
An integral
strip
designed to provide efficient
HEAD
airGASKET
circulation and
A filler material placed
dissipation of heat away from
between the cylinder block
the engine cylinder block
and PLUG
cylinder head to seal
SPARK
into the
air stream.
the
combustion
Component thatchamber.
isolates
Made
of
soft
metals
the electricity and and
graphite
together.
produceslayered
the spark
for the
engine
PARTS OF THE ENGINE
PISTON
A cylindrical engine component
that slides back and forth in the
cylinder bore
CONNECTING
ROD by forces produced
during the combustion process.
Engine component that
transfers motion from the
CRANKSHAFT
piston to the crankshaft and
functions
a lever arm.
An engineascomponent
that
converts linear (reciprocating)
motion of the piston into rotary
FLYWHEEL
motion.
A cast iron disk that is
mounted at one end of the
COUNTERWEIGHTS
crankshaft to provide inertia
A protruding
for
the engine.mass cast into the
crankshaft which partially
balances the forces of a
reciprocating piston.
PARTS OF THE ENGINE
PISTON
PISTON: A cylindrical engine component that
slides back and forth in the cylinder
bore by forces produced during the
combustion process.
PARTS OF THE ENGINE
PISTON
PISTON:
DIFFERENT PISTON TYPES:
FLAT
DOMED
IRREGULAR
DISHED
PARTS OF THE ENGINE
PISTON
PISTON RINGS:
Three types:
An expandable split ring used to provide a
seal between the piston and the cylinder
wall
1.
COMPRESSION RING
2.
WIPER RING
3.
OIL RING
1
2
3
PARTS OF THE ENGINE
VALVE TRAIN
VALVE HEAD
MARGIN
VALVE FACE
VALVE SEAT
VALVE NECK
VALVE GUIDE
VALVE SPRING
VALVE ROTATOR
VALVE SPRING RETAINER
FOUR STROKE CYCLE ENGINE
 INTAKE STROKE
COMPRESSION STROKE
 POWER STROKE
 EXHAUST STROKE
INTAKE STROKE
 Occurs from TDC to BDC
 Intake valve opens
 Air-Fuel that was previously
mixed in the carburetor is now
sucked into the combustion
chamber due to the low pressure
created inside.
COMPRESSION
STROKE
 Compresses the Air-Fuel
mixture
By compressing the Air-Fuel
mixture:
Allows for more energy to
be released.
Increases fuel
vaporization
Allows for more complete
burning
POWER
STROKE
 Spark occurs igniting
compressed air-fuel mixture
 Spark occurs 20 degrees before
TDC so the flame front can
spread throughout combustion
chamber
Gases ignite pushing piston
away from the cylinder head
Linear motion from the
piston is transferred into a
rotary motion on the
crankshaft
EXHAUST
STROKE
 Exhaust valve opens
 Inertia from the flywheel
and other parts push the
piston back up toward TDC,
pushing the spent gases out of
the combustion chamber.
THE END

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