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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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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

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Confirmation

Confirmation

Confirmation

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