L3 - Performance Metrics

Question 1

As the pressure ratio increases what happens to the isentropic efficiency of compressors and turbines?

Answer 1

Compressors get less efficient

Turbines get more efficient

Question 2

What are the three ways to increase thrust?

Answer 2

Increase mass flow
Increase Jet velocity
Make use of pressure thrust

Question 3

For high propulsive efficiency what is required?

Answer 3

Velocity of the jet must be similar to the aircraft speed, so mass flow is very important.

Question 4

What is the thermal efficiency?

Answer 4

A ratio of the energy gained against the energy contained in the fuel.

Question 5

What units if Specific Fuel Consumption

Answer 5

kg/hN

Question 6

What is Specific Thrust?

Answer 6

The thrust produced per unit mass air flow

Question 7

What variable must you be careful of when considering different temperatures?

Answer 7

Gamma. Different for hot and cool air.

Question 8

How does one calculate the combustion efficiency?

Answer 8

FARideal/FARactual