7/27/2019 Automobile Engine 4 Stroke Cycle ENGS100.pdf
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Automobile Engine
4 Stroke Cycle
7/27/2019 Automobile Engine 4 Stroke Cycle ENGS100.pdf
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Automobile: Main systems1. Engine – convert energy of fuel to energy of motion
2. Powertrain – transfer power from engine to driven wheels3. Brakes – slow and stop vehicle
4. Steering – control direction of travel
5. Suspension
– Absorb bumps – Maintain alignment
– Keep wheels in contact with road
6. Electrical – generate and distribute electricity
7. Body – protect occupants (
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Automobile: Main Theme
• Visually apparent how form follows function.
• Visually Accessible.
• How it works is there to see if look in the right
place.
• Components performing specific function in
overall system also very apparent.
• Systems and subsystems of components
contributing to overall operation also readily
apparent in automobile.
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Engine
Chemical energy of
fuel and air
Engine
Convert chemical to
Kinetic energy
(energy of motion)Fuel
Air
System Boundary – automobile engine
Exhaust
Heat
Kinetic Energy
Engine RPM
Start at location where air and fuel
are burned and work out from there.
Put the car together starting with
the combustion
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Engine: Underlying Principle
• Internal combustion engine
– Energy conversion device
– Heat engine
– Heat -> Work• Converts energy of fuel into energy of
motion.
• 4 –stroke cycle
• Otto cycle
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Engine Construction• Basic “generic” Internal
Combustion AutomobileEngine.
• Start where air/fuel are
burned and work out from
there.
• Strip off components
• Engine put together in
two halves – Upper half = head
– Lower half = block
– Seal between upper and
lower = head gasket
Engine head
Engine
Engine block
Engine head
gasket
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Engine Construction
• Look at single
cylinder • Most automobile
engines have more
than one cylinder • Same process in
each one
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Engine: Main Parts1. Cylinder – contain burning air/fuel – hole in
metal block
2. Piston – convert pressure of burning air/fuelto force – metal plug
3. Crank – convert linear to rotary motion –
crank-shaped metal
4. Connecting Rod – Transfer force from piston
to crank – metal bar
5. Spark plug – Ignite air/fuel mixture – Insulated gap
6. Intake port – allow air/fuel into cylinder –
hole in engine head
7. Intake valve – control flow through intake
port – upside down metal T
8. Exhaust port – allow exhaust to exit cylinder – hole in engine head
9. Exhaust valve – control flow through
exhaust port – upside down metal T
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Valves
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Crankshaft
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4-Stroke Cycle
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4-Stroke Cycle
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4-Stroke Cycle Details• Cams
– Open and close intake and exhaust valves.
– Camshaft: several cams connected together.
– OHC: Over head Cam, cam is above valves, allows higher engine speeds.
– DOHC: Double Overhead Cam, separate control of intake and exhaust valve to optimize performance.
• Timing Belt (also timing chain, timing gears) – Connects crankshaft to camshaft
– Coordinates opening and closing of valves with up and down motion of pistons.
– Insures that valves are opened and closed at proper time.
• Flywheel – Heavy metal disk at the end of the crankshaft.
– Helps to smooth out surges from the power strokes to keep engine rotating at a uniform rate.
•
• Rings – Help seal pistons to cylinder walls
• Firing Order
– Each cylinder in different part of the cycle
– Insures always one cylinder pushing the others
– Smooths out vibrations
– Distributes heat input to engine block
• Multi valve engines – Small valves move quicker
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Illustrations
• Form following function
• More than one design possible
– Valve trains
– Timing
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Firing Order
1 2 3 4
P E C I
E I P C
I C E P
C P I E
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Rings
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Rings
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Cams
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Valve Trains (Cam Variation)
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OHC and OHV
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OHV and OHC Valve Trains
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Timing
Connects crankshaft and camshaft
Coordinates valves and pistons
Gear Chain Belt
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Timing Belt
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Timing Chain
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Timing Gear
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Flywheel
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Multi Valve Engines• Normal Innovation
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Rotary Engine
http://upload.wikimedia.org/wikipedia/commons/f/fc/Wankel_Cycle_anim_en.gi
f
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