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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
What happens during compressor stall
Airflow slows down , stops or going in reverse direction
26
When does compressor stall occur
Low speed
27
What is a surge
Severe form of stall and happens in fwd or aft of compressor stage
28
What happens to thrust in a surge
It decreases which causes engine speed fluctuations and gas exhaust temperature to increase
29
What are the reasons for stall or surge
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
30
When can engine stall
If engine speed is too far behind design speed
31
What are the 3 methods of airflow control
1. Compressor bleed valve 2. Dual or triple spool rotor 3. Variable compressor stator vanes
32
What is most effective method of airflow control
Variable stator vanes
33
What’s a disadvantage of variable stator vane
Needs a complicated control mechanism
34
What does the Low Pressure Compressor & Turbine coupling do
Attaches and secures LPC Rotor to LPT shaft
35
What the purpose of a fan stator case
Flow path for discharge air
36
What type of component is a intermediate case
Major structural component
37
Spinner cone shape
Curved front or sharp tip
38
Spinner cone other names
Nose cone or compressor inlet cone
39
What does the spinner cone do
Creates smooth aerodynamic fairing at engine inlet
40
What material is a fan blade disc and where is it attached
Titanium alloy and fwd rotor shaft and rotor drum of the LPC
41
What shape is fan blade attachment
Dove tail fitting and a loose fit is necessary
42
What loads are on rotor blades
Air loads in the horizontal direction & centrifugal loads
43
What does a midspan shroud do
Keep flan blade deflection within safe limits
44
What does converting energy of fluttering blade into friction do
Dampens the fluttering
45
What is the LP compressor
Booster module
46
What slots does a drum have
Dovetail
47
What are the rings with sharp edges for in a drum
For the labyrinth seal which is used for efficiency
48
What’s the good thing about wide chord fan blades
More efficient and can be used at Low speeds while producing less noise
49
What’s the LPC stator case for
Enclosed rotor and supports stator vane
50
What the two types of construction methods for a LPC stator case
Closed and split
51
How many ring elements does a turbofan engine have
One or more
52
What’s the purpose of a flange
Stiffen case and prevent deformation
53
What does an acoustic panel do
Smooth surface for airflow & small holes on surface reduce noise
54
Construction of ring element
Honeycomb construction with Kevlar layers
55
What is an abradable shroud
Soft material that prevents damage if blades come into contact with shroud
56
When can fan blade be cut into shroud
High speeds , abradable shroud allowlist very small tip clearance for maximum efficiency
57
Where is the intermediate case and what’s another name for it
Positioned between LP and HP compressor and is know as fan frame
58
What does the intermediate case do
House variable bleed valves which protect against LPC surge
59
How are struts shaped
Aerodynamically shaped in areas where they reach through the fan duct and core engine duct
60
When does imbalance occur
Due to difference in momentum weighs between fan blades
61
Centrifugal force parameters
1. Rotor speed 2. Blade mass 3. Distance of CoG from rotational axis
62
What is the moment weight measured
1. Gram inches 2. Cmg 3. Oz inches
63
How do you know what method of fan blade change to do
Method is proposed by manufacturer
64
What’s the best method of fan blade change
Replace with the same moment weigh or as close of possible
65
Why do we offset the mounting hole
Makes tire spinner is in correct position
66
How is a rotor assembled in the HP compressor
By two or more integral drums or bolted to adjacent drum and separate disc
67
What’s does CDP seal do
Prevents discharge airflow going to bearing area below the combustion chamber
68
What is design principle in stator assembly
Allows closer clearances between blade lips and compressor case
69
How are stator vanes grouped
Into segments
70
How are stator frames installed
As single vanes
71
What’s the inner ends of the vane segment platform for
Minimise vibrations caused by airflow
72
On a variable stator vane where is the trunnion
Each end
73
What’s the outer trunnion for
Fits into a hole in the compressor case
74
How are trunnions installed
Together with an actuation lever
75
How are levers connected
To the same ring so they move simultaneously
76
Who selects position of high speed pick ups on the HPC
Manufacture
77
What is the source of bleed air for the pneumatic system
HPC
78
How is bleed air supplied
Hollow stator vanes or holes in outer platform off stator vanes
79
Where are bleed pick up holes located
Entire circumstance of case
80
What does the bleed manifold do
Collects air form pick up holes and supples it to the consumers

M15 GTE (19 decks)

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