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17-10-27
1
Aero Engines
9.01 Four Stroke Cycle and Engine Types References: FTGU pages 51-53
9.01 Four Stroke Cycle and Engine Types
MTPs:
– Parts of the Cylinder – 4 Stroke Cycle – Types of Combustion Engines
Parts of the Cylinder • Piston: moves up and down • Bore: hole for piston • Spark Plug(s): ignites fuel
• Valves: intake and exhaust
• Piston Rod: moves crankshaft • Crank Shaft: rotates prop
• Sump: contains oil at bottom • Cam: opens / closes valves
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4 Stroke Cycle
Induction (Suck)
• Cam pushes down Intake Valve
• Piston forced down by moving Crankshaft
• Down-moving piston sucks air/fuel mixture through intake valve
Cam Cam
Compression (Squeeze)
• Both valves closed
• Piston forced upwards by moving crankshaft
• Up-moving piston compresses air/fuel mixture
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Power (Bang)
• Both valves closed
• Spark plug ignites fuel air mixture
• Piston forced down by expanding gasses
• Down-moving piston pushes connecting rod which rotates crankshaft
Exhaust (Blow)
• Cam pushes exhaust valve open
• Piston forced upwards by moving crankshaft
• Up-moving piston pushes exhaust gasses out
Confirmation
Match the parts of a reciprocating engine by matching their names with the letter.
Cylinder ____
Crankshaft ____
Intake valve ____
Piston ____
Sparkplug ____
Connecting rod ____
Exhaust valve ____
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Confirmation Match the actions of a four-stroke cycle by matching the action with the engine diagram.
Compression ____
Exhaust ____
Intake ____
Power ____
Types of Combustion Engines
Horizontally Opposed
• Two banks of cylinders on opposite sides of a centrally located crankcase.
• Flat design fits inside aircraft nose well.
• Common in Cessna aircraft
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5
Radial • Odd number of cylinders (5, 7, 9…) surrounding a
centrally located crankshaft. • Single or multiple banks of engines may be used
(stacked behind one another). • Cylinders fire opposite each other to reduce vibrations. • Poor shape increases parasite drag and reduces forward
visibility.
Inline • Cylinders lined up behind each other, typically
underneath crankshaft (aka inverted inline). • Advantage: small frontal cross section
(streamlined aircraft nose) • Disadvantage: poor air cooling and long, heavy
crankshaft.
Confirmation
Match the engines with the correct engine type:
• A – Horizontally opposed engine • B – Radial engine • C – In line engine