M15.6

Question 1

What does the turbine provide power to?

Answer 1

The compressors and accessory gearbox

Question 2

Where do turbines extract energy from?

Answer 2

The hot gases from the combustion chamber

Question 3

What are the two types of turbines on gas turbine engines?

Answer 3

• radial flow (turns air 90)

- axial flow (air stays straight)

Question 4

What are the turbine stationary vanes also called?

Answer 4

Turbine nozzle guide vanes

Question 5

What does one stage consist of?

Answer 5

A stator and rotor

Question 6

How many stages does a radial flow turbine have?

Answer 6

Always one

Question 7

Where are radial flow turbines used?

Answer 7

On small gas turbines such as APU

Question 8

How many stages does an axial flow turbine have?

Answer 8

As many that is necessary for the job

Question 9

What does the turbine convert the gas energy from the combustion chamber into?

Answer 9

Torque

Question 10

What is the impulse-reaction turbine often called?

Answer 10

A reaction turbine

Question 11

What must turbine materials be able to withstand?

Answer 11

Extremely high temperatures and very high centrifugal forces

Question 12

How does corrosion from sulphuric acid occur?

Answer 12

Because of sulphur in fuel and high gas temperatures

Question 13

How is corrosion from sulphuric acid prevented?

Answer 13

By the correct use of fuel

Question 14

When would material deformation known as creep occur?

Answer 14

maximum engine power (When high centrifugal forces are applied over a long period of time with high temperatures)

Question 15

When creep happens does the material return back to its original shape?

Answer 15

No

Question 16

How can plastic deformation be limited?

Answer 16

By efficient cooling

Question 17

How does convection cooling work?

Answer 17

It puts cold air inside of the material to cool it down

Question 18

Where is convection cooling used?

Answer 18

Turbine nozzle guide vanes and turbine rotor blades

Question 19

What cooling method is the easiest?

Answer 19

Convection cooling

Question 20

How does impingement cooling work?

Answer 20

An insert is placed inside the blade and uses small holes to spray the inside of the blade

Question 21

How does film cooling work?

Answer 21

It uses air holes to put a cold film around the blade

Question 22

What type of turbine cooling method is the most efficient?

Answer 22

Film cooling

Question 23

What are the first stage nozzle guide vanes cooled by?

Answer 23

• convection
• impingement
• film cooling

Question 24

What are the first stage rotor blades cooled by?

Answer 24

• convection
• impingement
• film cooling

Question 25

What is the second stage nozzle guide vanes cooled by?

Answer 25

- convection | - impingement

Question 26

What is the second stage rotor blades cooled by?

Answer 26

-convection

Question 27

Why is using multiple cooling types a benefit?

Answer 27

Because its a good balance f costs, efficiency, and service life

Question 28

What is tip clearance?

Answer 28

The gap between the blade tip and casing

Question 29

If there is no clearance control system how much does fuel consumption increase by?

Answer 29

Four times higher than if there was one

Question 30

What is active clearance control system?

Answer 30

It’s a system that keeps the tip clearance as small as possible in all operating conditions

Question 31

What are spray rings?

Answer 31

They’re rings that go around the turbine cases to cool them down

Question 32

How do spray rings work?

Answer 32

They work by spraying air through tiny holes

Question 33

What shape are the spray rings on the low pressure turbines?

Answer 33

Circular

Question 34

What shape are the spray rings on the high pressure turbines?

Answer 34

Rectangular

Question 35

What is the job of a interstate seal?

Answer 35

To prevent gas flow trough the gap between the stator and the rotor

Question 36

What a re blade retainers designed to do?

Answer 36

Hold the blades in place so that they do not move

Question 37

Rotor blades on the high pressure turbine have special shaped roots, what are these called?

Answer 37

Fir tree root

Question 38

Why are fir tree roots used?

Answer 38

So forces can be transmitted smoothly which increases longer service life

Question 39

What are the two main types of turbine blades used today?

Answer 39

Open end blades and shrouded blades

Question 40

Where are open end turbine blades used?

Answer 40

High rotational speeds and high pressure turbines

Question 41

Where are shrouded turbine blades used?

Answer 41

Low pressure turbines and lower rotational speeds

Question 42

Why are shrouded blades used?

Answer 42

Because they reduce vibration by forming a band at the blade tips

Question 43

Where are the high pressure turbine blades cooled from?

Answer 43

They’re called internally from the high pressure compressor

Question 44

Why are the turbine frame struts hollow?

Answer 44

Gives room for oil supply lines, scavenge lines, oil drain lines

Question 45

What are the two types of turbine frame struts?

Answer 45

Radial struts and tangential struts

Question 46

Why are turbine frames with the radial struts designed as short as possible?

Answer 46

It minimises the expansion of the struts and keeps stress low

Question 47

Why would tangential struts be used on a turbine frame?

Answer 47

It minimises stress because if they expanded it will caused it to rotate slightly