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Module 15 > M15.4 Compressors > Flashcards

M15.4 Compressors Flashcards

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

A

Variable stator vanes

24
Q

Advantage of variable stator vanes

A

Optimum angle of attack for all speeds

25
Q

Disadvantage of variable stator vanes

A

Very complicated control mechanism

26
Q

What is used for feedback in the compressor control system

A

LVDT or RVDTs

27
Q

What controls the HP compressor bleed valves

A

ECU

28
Q

CIT?

A

Compressor Inlet Temperature

29
Q

CIT sensor location

A

Fan frame between the LP and HP compressor

30
Q

What actuates the VSVs

A

Fuel pressure

31
Q

What supplies the VSV fuel pressure

A

MEC or HMU

32
Q

What are the actuating rings that surround the respective compressor stage called

A

Unison rings

33
Q

Methods of VSV or VBV feedback

A
  • Electrical
  • Mechanical
34
Q

What is the usual electrical feedback components used in VSV or VBV feedback

A
  • LVDT
  • RVDT
35
Q

What is the position of the VBVs if the VSVs are open

A

Closed

They work in the opposite direction to each other

36
Q

Spinner cone purpose

A

Covers end the fan disk of rotor

Creates a smooth aerodynamic fairing

37
Q

Why is a spiral printed on to the spinner cone

A

Scare away birds

38
Q

Why is a loose fit necessary for fan blades

A

So that sudden forces or torque loads do not exceed the max limits

39
Q

Apart from loose fit what can be used to prevent the blades reaching the limit on longer blades

A

Shrouds

40
Q

In the LPC what is fitted in between the dovetail slots

A

Labyrinth seals

41
Q

On the fan case assembly what is used to stiffen the case and prevent deformation

A

Flanges

42
Q

What is used to reduce the noise of the fan

A

Acoustic panels

43
Q

Purpose of abradable shrouds

A

To allow very small top clearance

44
Q

What is used to prevent a fan blade from penetrating the fan case if it brakes off

A

Fan blade containment

45
Q

What carries the loads from the engine bearing to the engine mount

A

Fan frame struts

46
Q

Why are fan frame struts hollow

A

To save weight

47
Q

Why do all blades have different moment weight even if they have the same mass

A

CoG is different due to manufacturing tolerances

48
Q

Units of moment weight

A
  • Gram inches
  • Cmg
  • oz inches
49
Q

Where can the moment weight of a blade be found

A

On the root

50
Q

What information is found on the root of the fan blade

A
  • Part No
  • Serial No
  • Moment weight
51
Q

How can fan blade No.1 usually be located

A

An index mark on the fan disk or by an offset hole

52
Q

Where are balance weights for fan blades normally installed

A
  • Fan disk
  • In the spinner cone
53
Q

Where are attachment bolts in HPC normally used

A

Long blades in the first stages

54
Q

Why do the inner ends of the stator assemblies have an inner platform

A

To minimise the vibrations caused by airflow

55
Q

How is bleed air supplied from the HPC

A

Through hollow stator vanes or holes in the outer platform of the stator vanes

Module 15 (20 decks)

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