Module 15 > M15.4 Compressors > Flashcards

M15.4 Compressors Flashcards

(55 cards)

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1
Q

Compressor main components

A
  • Stator
  • Rotor
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2
Q

Compressor stage

A

One stator and one rotor

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3
Q

First part of compressor stage

A

Rotor

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4
Q

A set of stator vanes in front of a compressor stage us called what

A

Inlet guide vanes (IGV)

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5
Q

IGV purpose

A

Improve airflow onto the first stage

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6
Q

What are the stator vanes in the fan ducts usually named

A

Outlet Guide Vanes (OGV)

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7
Q

Types of compressor

A
  • Axial flow
  • Centrifugal flow
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8
Q

Centrifugal flow compressor parts

A
  • Impeller
  • Diffuser
  • Compressor manifold
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9
Q

Centrifugal flow pressure ratio

A

5:1

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10
Q

Two impellers are mounted face to face is called what

A

Double face compressor

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11
Q

Benefit of double face compressor

A
  • Weight saving
  • smaller engine frontal area
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12
Q

Axial flow compressor stage ratio

A

1:3:1

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13
Q

Why is the compressor cross section gradually decreased

A

Constant velocity of the airflow

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14
Q

What is the compressors design point

A

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

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15
Q

What is a severe form of compressor stall

A

Compressor surge

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16
Q

What are the effects of compressor surge

A
  • Decrease in thrust
  • Engine speed fluctuates
  • EGT increases
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17
Q

What area of the compressor is more efficient at low speeds

A

FWD

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18
Q

Methods to avoid stall or surge

A
  • Compressor bleed valves
  • Dual or triple spool rotors
  • Variable compressor stator vanes
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19
Q

When do compressor bleed valves open

A

Low speeds

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20
Q

Where are compressor bleed valves located

A

Mid or aft

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21
Q

The main disadvantage of compressor bleed valves

A

Massive loss of efficiency

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22
Q

Advantage of duel or triple spool compressors

A

Excellent acceleration capability

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23
Q

Most effective method of avoiding compressor stall and surge

Study These Flashcards
A

Variable stator vanes

24
Q

Advantage of variable stator vanes

Study These Flashcards
A

Optimum angle of attack for all speeds

25
Disadvantage of variable stator vanes
Very complicated control mechanism
26
What is used for feedback in the compressor control system
LVDT or RVDTs
27
What controls the HP compressor bleed valves
ECU
28
CIT?
Compressor Inlet Temperature
29
CIT sensor location
Fan frame between the LP and HP compressor
30
What actuates the VSVs
Fuel pressure
31
What supplies the VSV fuel pressure
MEC or HMU
32
What are the actuating rings that surround the respective compressor stage called
Unison rings
33
Methods of VSV or VBV feedback
- Electrical - Mechanical
34
What is the usual electrical feedback components used in VSV or VBV feedback
- LVDT - RVDT
35
What is the position of the VBVs if the VSVs are open
Closed They work in the opposite direction to each other
36
Spinner cone purpose
Covers end the fan disk of rotor Creates a smooth aerodynamic fairing
37
Why is a spiral printed on to the spinner cone
Scare away birds
38
Why is a loose fit necessary for fan blades
So that sudden forces or torque loads do not exceed the max limits
39
Apart from loose fit what can be used to prevent the blades reaching the limit on longer blades
Shrouds
40
In the LPC what is fitted in between the dovetail slots
Labyrinth seals
41
On the fan case assembly what is used to stiffen the case and prevent deformation
Flanges
42
What is used to reduce the noise of the fan
Acoustic panels
43
Purpose of abradable shrouds
To allow very small top clearance
44
What is used to prevent a fan blade from penetrating the fan case if it brakes off
Fan blade containment
45
What carries the loads from the engine bearing to the engine mount
Fan frame struts
46
Why are fan frame struts hollow
To save weight
47
Why do all blades have different moment weight even if they have the same mass
CoG is different due to manufacturing tolerances
48
Units of moment weight
- Gram inches - Cmg - oz inches
49
Where can the moment weight of a blade be found
On the root
50
What information is found on the root of the fan blade
- Part No - Serial No - Moment weight
51
How can fan blade No.1 usually be located
An index mark on the fan disk or by an offset hole
52
Where are balance weights for fan blades normally installed
- Fan disk - In the spinner cone
53
Where are attachment bolts in HPC normally used
Long blades in the first stages
54
Why do the inner ends of the stator assemblies have an inner platform
To minimise the vibrations caused by airflow
55
How is bleed air supplied from the HPC
Through hollow stator vanes or holes in the outer platform of the stator vanes
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