Turbines

Question 1

Function of turbine

Answer 1

Drive compressor and accessory gear box

Question 2

2 types of turbine

Answer 2

Radial and axial

Question 3

What type of turbine is most common on modern aircraft

Answer 3

Axial

Question 4

Advantages of axial turbine

Answer 4

Allows high airflow and creates high thrust , you can use as many stages as necessary

Question 5

What does the turbine convert

Answer 5

Convert has energy from combustion chamber into torque

Question 6

Two types of turbines

Answer 6

Impulse and reaction

Question 7

What turbine does modern aircraft use

Answer 7

Reaction turbine

Question 8

How can you prevent corrosion of turbine blades

Answer 8

Use correct jet fuel

Question 9

What is creep

Answer 9

Blades become elongated

Question 10

What factors effect creep

Answer 10

Material

Temperature

Time

Question 11

What does the rate of creep depend on

Answer 11

Speed and temperature, if the increase there is more creep

Question 12

How are HP nozzle guide vanes and rotor blades cooled

Answer 12

Air from engine HPC

Question 13

What’s the most effect type of cooling

Answer 13

Film Cooling

Question 14

How is plastic deformation limited

Answer 14

Efficient cooling of turbine materials

Question 15

What’s a negative of film cooling

Answer 15

Small holes are difficult to make and expensive

Question 16

Why is film cooling most effective

Answer 16

Maximum cooling effect with minimum cooling air which allows more air used to drive turbine

Question 17

How are nozzle guide vanes cooled in the second sage

Answer 17

Convection and impignet

Question 18

How are second stage rotor blades cooled

Answer 18

Convection only

Question 19

Two types of clearance control

Answer 19

Passive and active

Question 20

Where is passive used

Answer 20

HP & LP Turbines

Question 21

What’s the LP turbine cooling source

Answer 21

Fan air

Question 22

What’s an advantage of tip clearance control

Answer 22

Saves a lot of fuel

Question 23

How is clearance control valves controlled

Answer 23

Controlled by ECU and actuated by fuel pressure from hydro-mechanical unit

Question 24

When does active clearance control work

Answer 24

During climb and cruise

Question 25

When is active tip clearance most effective

Answer 25

When engine operates at high power for a long time

Question 26

At cruise how much of n2 is used

Answer 26

80-95%

Question 27

clearance control valve controlled with what motor

Answer 27

Torque motor

Question 28

What’s the parts of a Turbine construction

Answer 28

HPT , LPT , Turbine Frame

Question 29

Where is the turbine frame located

Answer 29

Behind low pressure turbine

Question 30

What loads do the turbine frame carry

Answer 30

Bearing loads of the aft end of LPT Transmits loads to rear engine mount on turbine frame

Question 31

How is the HPT case made

Answer 31

In one piece

Question 32

How are nozzle guide vanes in the HPT made

Answer 32

Vane segments with each segment having usually 2 nozzle guide vanes

Question 33

Where is the inner seal located

Answer 33

Inner surface of nozzle guide vane segments

Question 34

Components of a HPT Rotor

Answer 34

Turbine disc Rotor blade rotating interstate seal Fwd and rear blade retainers

Question 35

What’s an interstate seal

Answer 35

Acts as a spacer between 2 discs

Question 36

How are turbine blades held in place

Answer 36

Blade retainers

Question 37

What are the retainers in LP turbines

Answer 37

Strip type which fit into dovetail slots and are bent up at each end

Question 38

Rotor blade in HPT shape

Answer 38

Fir tree root

Question 39

Benefit of fir tree root design

Answer 39

Many contact surfaces

Question 40

What are the turbine blades used in rotor assembly

Answer 40

Open end and shrouded

Question 41

When are open end turbine blades used

Answer 41

Turbines with high rotational speeds

Question 42

How is the added weight in an shrouded blade in a LPT offset

Answer 42

Thinner blades which make it more efficient

Question 43

How are turbine discs installed

Answer 43

Directly splined or bolted

Question 44

How are HPT Blades cooled

Answer 44

Internal cooled by air form HPC

Question 45

What’s an aft major structural component

Answer 45

Turbine Frame

Question 46

What does the turbine frame support

Answer 46

1 or 2 turbine rotors & provides attachment points for the rear engine mount

Question 47

How big should a radial strut be

Answer 47

As short as possible to minimise expansion which keeps stress on frame hub low

Question 48

Tangengal struts minimise what

Answer 48

stress caused by thermal expansion