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M15 > M15.6 > Flashcards

M15.6 Flashcards

1
Q

What does the turbine provide power to?

A

The compressors and accessory gearbox

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2
Q

Where do turbines extract energy from?

A

The hot gases from the combustion chamber

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3
Q

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

A
  • radial flow (turns air 90)

- axial flow (air stays straight)

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4
Q

What are the turbine stationary vanes also called?

A

Turbine nozzle guide vanes

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5
Q

What does one stage consist of?

A

A stator and rotor

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6
Q

How many stages does a radial flow turbine have?

A

Always one

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7
Q

Where are radial flow turbines used?

A

On small gas turbines such as APU

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8
Q

How many stages does an axial flow turbine have?

A

As many that is necessary for the job

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9
Q

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

A

Torque

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10
Q

What is the impulse-reaction turbine often called?

A

A reaction turbine

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11
Q

What must turbine materials be able to withstand?

A

Extremely high temperatures and very high centrifugal forces

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12
Q

How does corrosion from sulphuric acid occur?

A

Because of sulphur in fuel and high gas temperatures

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13
Q

How is corrosion from sulphuric acid prevented?

A

By the correct use of fuel

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14
Q

When would material deformation known as creep occur?

A

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

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15
Q

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

A

No

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16
Q

How can plastic deformation be limited?

A

By efficient cooling

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17
Q

How does convection cooling work?

A

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

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18
Q

Where is convection cooling used?

A

Turbine nozzle guide vanes and turbine rotor blades

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19
Q

What cooling method is the easiest?

A

Convection cooling

20
Q

How does impingement cooling work?

A

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

21
Q

How does film cooling work?

A

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

22
Q

What type of turbine cooling method is the most efficient?

A

Film cooling

23
Q

What are the first stage nozzle guide vanes cooled by?

A
  • convection
  • impingement
  • film cooling
24
Q

What are the first stage rotor blades cooled by?

A
  • convection
  • impingement
  • film cooling
25
Q

What is the second stage nozzle guide vanes cooled by?

A
  • convection

- impingement

26
Q

What is the second stage rotor blades cooled by?

A

-convection

27
Q

Why is using multiple cooling types a benefit?

A

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

28
Q

What is tip clearance?

A

The gap between the blade tip and casing

29
Q

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

A

Four times higher than if there was one

30
Q

What is active clearance control system?

A

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

31
Q

What are spray rings?

A

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

32
Q

How do spray rings work?

A

They work by spraying air through tiny holes

33
Q

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

A

Circular

34
Q

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

A

Rectangular

35
Q

What is the job of a interstate seal?

A

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

36
Q

What a re blade retainers designed to do?

A

Hold the blades in place so that they do not move

37
Q

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

A

Fir tree root

38
Q

Why are fir tree roots used?

A

So forces can be transmitted smoothly which increases longer service life

39
Q

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

A

Open end blades and shrouded blades

40
Q

Where are open end turbine blades used?

A

High rotational speeds and high pressure turbines

41
Q

Where are shrouded turbine blades used?

A

Low pressure turbines and lower rotational speeds

42
Q

Why are shrouded blades used?

A

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

43
Q

Where are the high pressure turbine blades cooled from?

A

They’re called internally from the high pressure compressor

44
Q

Why are the turbine frame struts hollow?

A

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

45
Q

What are the two types of turbine frame struts?

A

Radial struts and tangential struts

46
Q

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

A

It minimises the expansion of the struts and keeps stress low

47
Q

Why would tangential struts be used on a turbine frame?

A

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

M15 (15 decks)

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