15.1 Fundamentals

Question 1

What is a change of state in terms of airflow through the engine?

Answer 1

A thermal process which entails a transformation of heat energy into mechanical

Question 2

What are the four ideal changes of state and which are of importance in gas turbine engines?

Answer 2

-isobaric
-isochric
-isothermal
-isentropic

(Isobaric isentropic)

Question 3

What is the compressors function?

Answer 3

To increase static pressure

Question 4

What turns the compressor?

Answer 4

The turbine

Question 5

What is potential energy?

Answer 5

Energy contained virtue of its position

Question 6

What is kinetic energy?

Answer 6

Energy contained virtue of its motion

Question 7

What is the formula for potential energy?

Answer 7

PE = mgh

Mass = M
Gravity = gravitational constant
Height = height

Question 8

What is the formula for kinetic energy?

Answer 8

2
KE = 1/2 mv

Mass = m
Velocity = v

Question 9

What is Newton’s first law?

Answer 9

The law of inertia

Question 10

What is Newton’s second law?

Answer 10

Force = mass x acceleration

Question 11

What is Newton’s third law?

Answer 11

Every action has an equal and opposite reaction

Question 12

What are the stages of the Brayton cycle?

Answer 12

-intake
-compress
-combust
-exhaust

Question 13

What is the working fluid in a gas turbine engine?

Answer 13

Air

Question 14

What is isobaric heating?

Answer 14

Volume increases pressure remains the same

Question 15

Where does isobaric heating occur?

Answer 15

The combustion chamber

Question 16

Where is the highest pressure in the engine?

Answer 16

The inlet of the combustion chamber

Question 17

Where is the highest temperature in the engine?

Answer 17

Rear of the combustion chamber/ the first stage nozzle guide vane

Question 18

What is isentropic compression?

Answer 18

Pressure increases volume decreases

Question 19

What is a brayton cycle?

Answer 19

The thermodynamic cycle of a gas turbine engine

Question 20

What is the formula for work?

Answer 20

Force x distance
Expressed in joules or nm

Question 21

What is the formula for power?

Answer 21

Work/time
Expressed in watts

Question 22

What is motion?

Answer 22

A continuous change of position or place

Question 23

What is acceleration?

Answer 23

The rate of change of velocity

Question 24

What is the formula of acceleration?

Answer 24

Change in velocity (m/s) / time (s)

Question 25

What is speed?

Answer 25

How fast an object is moving/ the time it takes for an object to mover a distance

Question 26

What is velocity?

Answer 26

Speed with direction

Question 27

What are the characteristics of a turbojet engine?

Answer 27

Good
-efficient at high speed
-compact

Bad
-high fuel consumption
-poor performance at low speed
-limited range and endurance

Question 28

What are the characteristics of turbofan engines?

Answer 28

Good
-They produce 80% of their thrust with front mounted fans
-They are more efficient then turbojet
Bad
-inefficient at high altitudes
-heavier
-large frontal area

Question 29

What are the characteristics of turboprop engines?

Answer 29

-Using the turbo jet principle and applies the force to a propellor for small commuter aircraft
-it has additional turbines to try and produce shaft horsepower only
-very fuel efficient
-most efficient at mid altitude and mid speed
-the gearing systems are heavy

Question 30

What are the characteristics of turboshaft engines?

Answer 30

-It uses the shaft to power machinery
-small and light (APU)
-high power to weight
-smaller than a piston engine
-loud
-the gear systems can be complex

Question 31

What are the characteristics of piston engines?

Answer 31

Fuel efficient
Poor at high altitudes
In very small aircraft

Question 32

What is a twin spool vs a three spool turbine arrangement?

Answer 32

A twin spool has a turbine powering the low pressure compressor and the fan with a turbine powering the high pressure compressor
A three spool has a third spool dedicated to the fan

Question 33

What is important to remember regarding spools?

Answer 33

-They operate independently
-it’s effectively a turbine powering a compressor

Question 34

What is the gas generator in turbo prop engine?

Answer 34

The compressor, combustor and turbine

Question 35

Where are cobalt materials used?

Answer 35

Hot areas

Question 36

What are the characteristics of materials used in engines that are most desirable?

Answer 36

Strong enough and cheap