piston aerodynamic engine 1
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Piston Aerodynamic Engine
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3.1 Background
Dec 1903, Orville and Wilbur 1st flight with simple 4 cylinder piston
engine, 77kg,12 hp
The late 1850s piston steam engine
1862 Otto cycle invented (Nikolaus Otto, Germany) success in 1876
1903 Wright brothers designed and build their own engines, with
aluminum cast blocks
WW I (1914-1918), WW II (1939-1945) : Reciprocating engines. Till
today airplanes that speeds less than 483 km/hr
Max piston engine power 1000 hp, less than Turboprop/Turboshaft.
Gas turbine used less expensive kerosene-based fuel
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3.2 Engine Types
Boxer:
cost, weight, balance
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SI : Spark Ignition (Otto)
CI : Compression Ignition(Diesel)
(T )
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Power
4-stroke : 1 power/ 2 rev
2-stroke : 1 power/ 1 rev
imechBWW
Mean effective pressure (MEP or Pme): Power/Volume
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Cooling
Air cooled
Liquid cooled
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Supercharger/Turbocharger
Pressure decrease with altitude Power decrease
Used air compressor compensate pressure at
high altitude
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Supercharger/Turbocharger
Supercharger is drive by engine power
Turbocharger is drive by turbine that located at exhaust
Can be combined for high efficiency
Variable speed and multi stage
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Gas turbine Propeller Engines
1 Turboprop engines
Similar to turbojet, but with additional stage in turbine
Most power to drive propeller, but some jet thrust
Aircraft with short take-off and landing or requiring a
high propulsive efficiency at medium subsonic speed
2 Turboshaft engines
Similar to turboprop, but with additional turbine. No jet
thrust
Helicopter Ships, tank, hovercraft
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3.3 Thrust
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Thrust related to pressure
From Bernoullis
Therefore:
Example 3.1
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3.4 Combustion
Aviation Fuel
Hydrocarbon fuels, since 1903
Air & Fuel mixing with carburetor or direct injection
Aviation Gasoline: Avgas High octane
Gas turbine and diesel used kerosene base fuel
Knocking : Pre-ignition loss performance
Theoretical Air-Fuel mixture : Stoichiometric
Air-to-fuel ratio (AFR) for Isooctane is 15.1
stoichAFRAFR
stoichAFRAFR
Rich mixture:
Weak (lean) mixture :FR
AFRstoich
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Example 3.2
Find stoichiometric of Avgas, assume isooctane
Air : 79% N2 + 21% O2 1mole of O2 3.76mole of N2
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