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Flashcards in Performance Metrics Deck (9)
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List 5 examples of performance metrics

Polytropic efficiency
Propulsive efficiency
Overall efficiency
Specific fuel consumption
Specific thrust


What is the relationship between compressor efficiency and pressure ratio?

It is found that the compressor efficiency tends to decrease as the pressure ratio for which a compressor is designed increases


What's the definition of polytropic efficiency?

The isentropic efficiency for an elemental stage in a process such that it is constant through the whole process


What's the definition of propulsive efficiency?

The ratio of thrust power to the sum of thrust power and jet kinetic power


What do you want for high propulsive efficiency?

Jet velocity must be higher than the aircraft velocity (but not too much higher)


What is the efficiency of energy conversion?

A measure of how much kinetic energy is gained by the engine jet relative to the energy contained in the fuel


What is the definition of overall efficiency?

The ratio of the work done in overcoming drag to the energy supplied by the fuel


What is the definition of specific fuel consumption (SFC)?

Fuel consumption per unit thrust


What is the definition of specific thrust?

The thrust per unit mass of air flow