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Module 15 > M15.6 Turbine Section > Flashcards

M15.6 Turbine Section Flashcards

1
Q

Types of turbines

A
  • Radial flow
  • Axial flow
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2
Q

How many stages to a Radial flow turbine

A

Always a single stage

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3
Q

Advantage and disadvantage of radial flow turbine

A

Adv - Simple and easy to manufacture

Dissad - Less efficient

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4
Q

Duct shape between NGV and turbine blades

A

Convergent

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5
Q

Name of turbine which only uses the impact of the gas flow

A

Impact turbine

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6
Q

When does turbine creep occur

A

When centrifugal loads are applied over a long period of time

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7
Q

Do the turbine blades return to the same shape after turbine creep

A

No, it goes into the inelastic region

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8
Q

What can cause an increase in the rate of creep

A

High engine speeds and temp

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9
Q

What is the function of centrifugal force, material temp and time named

A

Creep

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10
Q

Easiest method of HPT cooling

A

Convection

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11
Q

Where is HOT cooling used

A
  • At the turbine NGV
  • Turbine rotor blades
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12
Q

Most effective type of turbine cooling

A

Film cooling

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13
Q

Disadvantage of film cooling

A

Difficult to drill holes so expensive

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14
Q

What is used to cool NGV and first stage rotor blades

A
  • Convection
  • Impingement
  • Film cooling
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15
Q

What is used to cool second stage NGVs

A
  • Convection
  • Impingement
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16
Q

How much tip clearance can cause a 1% fuel increase

A

0.25mm or 0.01”

17
Q

How much fuel is used with a 1% fuel increase

A

Approx 30,000kg per engine

18
Q

What expands faster in the turbine

A

Turbine casing

19
Q

What air is used in active clearance control

A

Fan or compressor bleed

20
Q

Types of clearance control

A

Active

Passive

21
Q

Where is air from the fan used in passive clearance control

A

LP turbine

22
Q

Difference between active and passive clearance control

A

Active controls the amount of air used

23
Q

If HP compressor air is used for ACC where is the air taken from

A

Intermediate stages or the last stages

24
Q

What controls and actuates active clearance control valves

A
  • ECU controlled
  • HMU actuated
25
Q

What signals does the main engine control require for active clearance control

A

Altitude

N2 = 80-95%

26
Q

Function of turbine disks

A

Hold rotor blades and transfer the torque from the blades to the compressor rear shaft

27
Q

What is located between the two turbine disks

A

Interstage seal

28
Q

HPT root shape

A

Fir tree root

29
Q

Why are fir tree root HPT blades used

A

Longer service life

30
Q

Types of turbine blades

A
  • Open end
  • Shrouded end
31
Q

Where are shrouded turbine blades normally located

A

LPT

32
Q

Turbine frame strut arrangements

A
  • Radial struts
  • Tangential struts
33
Q

What do tangential struts minimise

A

Stress due to thermal expansion

(Rotate hub slightly)

Module 15 (20 decks)

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