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

piston aerodynamic engine 1

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