Basic Turbine Engine Theory

Question 1

What is the basic description of the function of a turbine engine?

Answer 1

Air is drawn or rammed via intake, into a multi-stage compressor, fuel is added and ignited in the combustor, and the air is expanded through the turbine stages before being expelled out the back of engine.

Question 2

How is Newton’s second law mathematically expressed?

Answer 2

Force = mass x acceleration or F = Ma

Question 3

What is Newton’s 3rd law?

Answer 3

For every action there is an equal and opposite reaction.

Question 4

What is the practical application of Newton’s 3rd law?

Answer 4

Jet thrust

Question 5

How is thrust produced in a turbojet or turbofan engine?

Answer 5

By accelerating a mass of air through the engine.

Question 6

What is Charles’s law?

Answer 6

Charles’s Law states that at constant pressure, the volume of a given mass of gas is directly proportional to its absolute temperature.

Question 7

What is Boyle’s law?

Answer 7

Boyle’s law states that at constant temperature, the pressure and the volume of gas are inversely proportional.

Question 8

How does temperature, density, pressure and velocity of a gas flow vary through a convergent duct at subsonic speed?

Answer 8

Temperature, density and pressure reduce and velocity increases.

Question 9

How does temperature, density, pressure and velocity of a gas flow vary through a divergent duct at subsonic speed?

Answer 9

Temperature, density and pressure increase and velocity reduces.

Question 10

How does temperature, density, pressure and velocity of a gas flow through a convergent duct at supersonic speed?

Answer 10

Temperature, density and pressure increase and velocity reduces.

Question 11

How does temperature, density, pressure and velocity of a gas flow vary through a divergent duct at supersonic speed?

Answer 11

Temperature, density and pressure reduce and velocity increases.

Question 12

Where does subsonic flow decrease in velocity and increase in pressure?

Answer 12

Through a divergent duct.

Question 13

Where does subsonic flow increase in velocity and decrease in pressure?

Answer 13

Through a convergent duct.

Question 14

Where does supersonic flow decrease in velocity and increase in pressure?

Answer 14

Through a convergent duct.

Question 15

Where does supersonic flow increase in velocity and decrease in pressure?

Answer 15

Through a divergent duct.

Question 16

What property is exhibited by accelerating gas flow?

Answer 16

That the total energy is constant.

Question 17

Where in a turbofan engine is the pressure highest?

Answer 17

In the diffuser.

Question 18

Where in a turbojet engine is gas velocity highest?

Answer 18

Exiting the exhaust nozzle.

Question 19

Where in a turbine engine is the gas temperature highest?

Answer 19

At the flame in the combustion chamber.

Question 20

How does gas pressure vary as it passes through the combustion chamber?

Answer 20

It remains nearly constant, reducing very slightly due to the construction inefficiencies.

Question 21

How does gas temperature and velocity cart as it passes through the combustion chamber?

Answer 21

Temperature and velocity both increases.

Question 22

How does gas pressure, temperature and velocity vary as it passes through the turbine section?

Answer 22

Pressure and temperature progressively reduce, and velocity increases through the nozzle guide vanes and staters and reduces through the turbine blades.

Question 23

Why is the Brayton Cycle in a turbine engine referred to as an open or continuous cycle?

Answer 23

Because intake, compression combustion and exhaust are all occurring at the same time.

Question 24

What are the basic sections of a turbine engine? 5

Answer 24

The intake, the compressor, the combustion chamber, the turbine and the exhaust section.