Engines 1: Principles of Gas Turbine/Reciprocating Engines

Question 1

What is the relationship between pressure and velocity in a closed system?

Answer 1

They have an inverse relationship and together they make up total pressure

Pressure = static pressure
Velocity = dynamic pressure

Question 2

What happens to subsonic airflow as it goes through a convergent opening?

Answer 2

Pressure decreases
Velocity increases

Question 3

What happens to subsonic airflow as it goes through a divergent opening?

Answer 3

Pressure increases
Velocity decreases

Question 4

What happens to supersonic airflow as it goes through a convergent opening?

Answer 4

Pressure increases
Velocity decreases

Question 5

What happens to supersonic airflow as it goes through a divergent opening?

Answer 5

Pressure decreases
Velocity increases

Question 6

What does a nozzle do? (Relating to pressure and velocity)

Answer 6

A nozzle increases velocity

Question 7

What does a diffuser do? (Relating to pressure and velocity)

Answer 7

A diffuser increases pressure

Question 8

What are the three sections of a gas turbine engine?

Answer 8

Compressor
Combustion chamber/burner
Turbine

Question 9

What cycle is used in a gas turbine engine?

Answer 9

The Brayton cycle

Question 10

What cycle is used in a reciprocating engine?

Answer 10

The Otto cycle

Question 11

What are the steps to the Otto cycle?

Answer 11

Intake
Compression
Combustion
Exhaust

Question 12

What are the differences between the Brayton and the Otto cycle?

Answer 12

The Otto cycle happens sequentially and in a single piston whereas the Brayton cycle happens all at the same time in a single gas turbine engine/

Question 13

Gross thrust

Answer 13

Thrust measured at exhaust at standard day conditions (29.92in-hg and 15 °C)

Only produced by stationary engines

Question 14

Net thrust

Answer 14

Thrust measured under normal flight conditions

Accounts for inlet airflow velocity

Question 15

What are the factors that affect thrust?

Answer 15

Temperature
Altitude
Pressure
Engine RPMs
Ram Effect

Question 16

What is the relationship between thrust and air temperature?

Answer 16

Inversely related; as air temperature increases, thrust decreases

As it gets warmer, air molecules tend to move apart

Question 17

What is the relationship between thrust and air pressure?

Answer 17

Directly related; as air pressure increases, thrust increases

Higher air pressure means that air molecules tend to move closer together

Question 18

What is the relationship between thrust and altitude?

Answer 18

Inverse Relationship; thrust decreases as altitude increases

The thrust decrease (from the pressure decrease) outweighs the thrust increase (from the temperature decrease) as altitude increases

Question 19

What is the optimal cruise level?

Answer 19

36,000 ft

Question 20

How does ram effect change thrust at subsonic speeds?

Answer 20

At subsonic speeds, an increase in airspeed leads to a small increase in thrust

Question 21

How does ram effect change thrust at supersonic speeds?

Answer 21

At supersonic speeds, an increase in airspeed leads to a significant increase in thrust

Question 22

What is the relationship between engine RPMs and thrust?

Answer 22

Directly related; as engine RPMs increase, thrust increases

Question 23

Engine Pressure Ratio

Answer 23

Indicates the pressure ratio between the inlet and exhaust airflow

Question 24

Torquemeter

Answer 24

Indicates amount of power available

Shows shaft horsepower available to drive a propeller

Question 25

Tachometer

Answer 25

Indicates engine performance

Shows amount of energy produced by engine in %RPMs

Question 26

What is the relationship between thrust and RAM effect?

Answer 26

Direct relationship; as Ram Effect increases, thrust increases