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M15 GTE > Compressors > Flashcards

Compressors Flashcards

1
Q

Two main commoners in a compressor

A

Rotor and stator

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2
Q

What’s a rotor used for

A

Increase velocity

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3
Q

What’s a stator used for

A

Guide airflow to next rotor and increase static pressure

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4
Q

What different about a turbo shaft engine

A

Uses twin spool engine with reverse flow combustion

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5
Q

What’s the two types of stator vanes

A

First is called inlet guide vane

Second is called outlet guide vane

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6
Q

What are the two types of cases

A

Inlet and outlet case

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7
Q

What’s the purpose of a case

A

Give support for compressed rotor bearings and improve & strength airflow in and out of compressors

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8
Q

Two types of compressors

A

Axial flow and Centrifugal flow

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9
Q

Where is centrifugal flow compressors used

A

Small GTE such as apus

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10
Q

Centrifugal compressor pressure ratio

A

5:1

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11
Q

What are the parts of the centrifugal compressor

A

Impeller which is a rotor

Diffuser which is a stator

Compressor manifold which is compressor housing

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12
Q

What is maximum stages in a centrifugal compressor

A

Maximum 2 stages anymore and it becomes inefficient due to pressure decrease when air changes direction

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13
Q

What’s the purpose of a double face compressor

A

Higher airflow because air can enter from both sides without changing pressure

Saves weight and has a smaller frontal area

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14
Q

What axis is axial flow along

A

Horizontal

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15
Q

How is air slowed down in axial flow

A

Use of divergent duct which is a diffuser like shape

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16
Q

Axial flow pressure ratio

A

1:3:1

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17
Q

What’s the need for a tapered compressor case

A

Reduces cross sectional area which maintains axial velocity

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18
Q

What is design point

A

Optimum operating condition for a given pressure ratio , rotational speed and airflow

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19
Q

What is resultant rotor inlet velocity

A

Direction of airflow

Sum of air inlet velocity and rotor speed

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20
Q

Why is a small angle of attack to blades necessary

A

Allows airflow into rotor to be smooth

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21
Q

What does a stator do in an axial compressor

A

Decelerate airflow and guide to next compressor

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22
Q

What is the condition for speed for normal flow in an axial compressor

A

Only optimum at one compressor speed

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23
Q

What is the compressor stage

A

Rotor and stator together

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24
Q

What happens during stall

A

Airflow separates from compressor aero foils and causes turbulent vortex

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25
Q

What happens during compressor stall

A

Airflow slows down , stops or going in reverse direction

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26
Q

When does compressor stall occur

A

Low speed

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27
Q

What is a surge

A

Severe form of stall and happens in fwd or aft of compressor stage

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28
Q

What happens to thrust in a surge

A

It decreases which causes engine speed fluctuations and gas exhaust temperature to increase

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29
Q

What are the reasons for stall or surge

A

1.Damaged rotor blades or stator vanes

2.Dents or ice in engine inlet

3.Dirty compressor blades

4.Damaged turbine or broken objects in exhaust

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30
Q

When can engine stall

A

If engine speed is too far behind design speed

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31
Q

What are the 3 methods of airflow control

A
  1. Compressor bleed valve
  2. Dual or triple spool rotor
  3. Variable compressor stator vanes
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32
Q

What is most effective method of airflow control

A

Variable stator vanes

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33
Q

What’s a disadvantage of variable stator vane

A

Needs a complicated control mechanism

34
Q

What does the Low Pressure Compressor & Turbine coupling do

A

Attaches and secures LPC Rotor to LPT shaft

35
Q

What the purpose of a fan stator case

A

Flow path for discharge air

36
Q

What type of component is a intermediate case

A

Major structural component

37
Q

Spinner cone shape

A

Curved front or sharp tip

38
Q

Spinner cone other names

A

Nose cone or compressor inlet cone

39
Q

What does the spinner cone do

A

Creates smooth aerodynamic fairing at engine inlet

40
Q

What material is a fan blade disc and where is it attached

A

Titanium alloy and fwd rotor shaft and rotor drum of the LPC

41
Q

What shape is fan blade attachment

A

Dove tail fitting and a loose fit is necessary

42
Q

What loads are on rotor blades

A

Air loads in the horizontal direction & centrifugal loads

43
Q

What does a midspan shroud do

A

Keep flan blade deflection within safe limits

44
Q

What does converting energy of fluttering blade into friction do

A

Dampens the fluttering

45
Q

What is the LP compressor

A

Booster module

46
Q

What slots does a drum have

A

Dovetail

47
Q

What are the rings with sharp edges for in a drum

A

For the labyrinth seal which is used for efficiency

48
Q

What’s the good thing about wide chord fan blades

A

More efficient and can be used at Low speeds while producing less noise

49
Q

What’s the LPC stator case for

A

Enclosed rotor and supports stator vane

50
Q

What the two types of construction methods for a LPC stator case

A

Closed and split

51
Q

How many ring elements does a turbofan engine have

A

One or more

52
Q

What’s the purpose of a flange

A

Stiffen case and prevent deformation

53
Q

What does an acoustic panel do

A

Smooth surface for airflow & small holes on surface reduce noise

54
Q

Construction of ring element

A

Honeycomb construction with Kevlar layers

55
Q

What is an abradable shroud

A

Soft material that prevents damage if blades come into contact with shroud

56
Q

When can fan blade be cut into shroud

A

High speeds , abradable shroud allowlist very small tip clearance for maximum efficiency

57
Q

Where is the intermediate case and what’s another name for it

A

Positioned between LP and HP compressor and is know as fan frame

58
Q

What does the intermediate case do

A

House variable bleed valves which protect against LPC surge

59
Q

How are struts shaped

A

Aerodynamically shaped in areas where they reach through the fan duct and core engine duct

60
Q

When does imbalance occur

A

Due to difference in momentum weighs between fan blades

61
Q

Centrifugal force parameters

A
  1. Rotor speed
  2. Blade mass
  3. Distance of CoG from rotational axis
62
Q

What is the moment weight measured

A
  1. Gram inches
  2. Cmg
  3. Oz inches
63
Q

How do you know what method of fan blade change to do

A

Method is proposed by manufacturer

64
Q

What’s the best method of fan blade change

A

Replace with the same moment weigh or as close of possible

65
Q

Why do we offset the mounting hole

A

Makes tire spinner is in correct position

66
Q

How is a rotor assembled in the HP compressor

A

By two or more integral drums or bolted to adjacent drum and separate disc

67
Q

What’s does CDP seal do

A

Prevents discharge airflow going to bearing area below the combustion chamber

68
Q

What is design principle in stator assembly

A

Allows closer clearances between blade lips and compressor case

69
Q

How are stator vanes grouped

A

Into segments

70
Q

How are stator frames installed

A

As single vanes

71
Q

What’s the inner ends of the vane segment platform for

A

Minimise vibrations caused by airflow

72
Q

On a variable stator vane where is the trunnion

A

Each end

73
Q

What’s the outer trunnion for

A

Fits into a hole in the compressor case

74
Q

How are trunnions installed

A

Together with an actuation lever

75
Q

How are levers connected

A

To the same ring so they move simultaneously

76
Q

Who selects position of high speed pick ups on the HPC

A

Manufacture

77
Q

What is the source of bleed air for the pneumatic system

A

HPC

78
Q

How is bleed air supplied

A

Hollow stator vanes or holes in outer platform off stator vanes

79
Q

Where are bleed pick up holes located

A

Entire circumstance of case

80
Q

What does the bleed manifold do

A

Collects air form pick up holes and supples it to the consumers

M15 GTE (19 decks)

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