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Lecture 5: Propulsion

Jason Mickey

For AE 440 A/C LectureSeptember 2009

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Propulsion Responsibilities

• Select engine type and number of engines• Find an engine that meets power requirements• Determine SFC and fuel consumption • Determine propulsion system integration losses• Design fuel system and fuel tanks

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Engine Classifications

Engines

Reciprocating Turbine

Externally-driven Internally-driven

Turbofan Ramjet/ScramjetTurbojetTurboprop Propfan

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Engine Considerations

• Specific Fuel Consumption

• Thrust

• Weight

• Size

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Typical Engine SFC

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Part-Power Operation

Throttling back jet engines increases SFC

Approximated by

0.8

0.8

0.1 0.24 10.66 0.1

max max max

max maxmax

SFC T TM

SFC dry T dry T dryT TTT dry T dryT dry

(13.9)

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Altitude Effect on SFC

McCormick, Fig. 6.34

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Inlet Locations

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Inlet Types

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Propeller Locations

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Nozzle Types

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Installed Thrust

where

available idealT T1 1

0 0Inletlost ramref actual

P PP C

P P

1.3511 0.075 1

0 ref

PM

P

(13.5)

(13.6)

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Installed Thrust

• Other causes of decreased thrust include– Drag caused by the engine– Air bleed– Power extraction

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Altitude Effect on Thrust

McCormick, Fig. 6.34

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Suggestions for PDR

• Choose an engine

• Verify that power requirements are met for all phases of the mission

• Trade studies

• Give reasons for your decisions!