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Aircraft General Knowledge > Gas Turbine Compressor > Flashcards

Gas Turbine Compressor Flashcards

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1
Q

The less work the turbine has to do to drive the compressor, the more energy is
left to generate blank

A

Thrust

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2
Q

Modern designs achieve up to X:1. compression ratio in an axial compressor

A

35:1

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3
Q

Axial flow compressor; Air flows parallel to the blank

A

Axial flow compressor; Air flows parallel to the axis of the engine

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4
Q

What happens to pressure in a divergent duct.

A

Increases.

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5
Q

What happens to tempurature in a divergent duct.

A

Increases

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6
Q

What happens to velocity in a divergent duct.

A

Increases

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7
Q

What happens to velocity in a divergent duct in a centrifugal compressor?

A

Increases

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8
Q

What happens to pressure in a centrifugal diffuser?

A

Increases

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9
Q

What happens to tempurature in a centrifugal diffuser?

A

Increases

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10
Q

What happens to velocity in a centrifugal diffuser?

A

Decreaser

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11
Q

What compressor cannot aero dynamically stall?

A

Centrifugal

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12
Q

Generally, a maximum compression ratio of X:1 per stage can be achieved in centrifugal compressor

A

4.5

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13
Q

To achieve a greater mass flow the impeller can be blank: a double entry
impeller in a centrifugal compressor.

A

Double sided.

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14
Q

To achieve a greater blank the impeller can be double-sided: a double entry
impeller in a centrifugal compressor

A

Mass flow

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15
Q

All large commercial designs use blank compressor

A

Axial flow

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16
Q

A rotor + a stator = blank

A

A stage

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17
Q

Rotor adds blank to the airflow.

A

Energy

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18
Q

The pressure rise across a single stage is usually only about blank%

A

10-20

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19
Q

The partial breakdown of airflow through an engine is also known as what?

A

A stall

20
Q

a complete reversal of the airflow through the compressor is know as a what?

A

Deep surge

21
Q

Gas turbine engines have a very narrow operating band, limited by the air mass
flow and the overall pressure ratio. Beyond this operating band the compressor
becomes blank.

A

Unstable

22
Q

What happens to the pressure ratio at high rpms?

A

Increases

23
Q

What rpm would you have a higher margin of safety?

A

High

24
Q

A stall results in reduced blank through the compressor and thus reduced thrust

A

Air mass flow

25
Q

If fuel flow isn’t reduced the combustion temperature will quickly rise. The principal
symptoms of compressor stall is a high blank

A

EGT

26
Q

In an extreme case flames may be seen exiting the intake:
• This is blank and is often accompanied by a loud bang

A

Deep surge

27
Q

Over-fueling can cause a surge by creating excessive blank in the combustor:
• Over-fueling surge has been mostly eliminated by modern electronic fuel control units.

A

Pressure

28
Q

What is a variable inlet guide vane used for?

A

Prevent stall/surge

29
Q

What is a variable inlet guide vane?

A

They change aoa to prevent stall

30
Q

Why are multiple stool compressors used?

A

To prevent stall

31
Q

(Handling bleeds) Inter-stage bleed valves vent pressure during the start to improve the axial flow
across the blank

A

Compressor

32
Q

Generally, the valves are blank (under spring pressure) with the engine switched
off and gradually close, to become fully blank at ground idle speed

A

Open - closed

33
Q

If a compressor stall occurs, quickly establish straight flight and blank the blank blank

A

Close the thrust leavers

34
Q

What would you find on a Lp compressor fan blade?

A

Snubber

35
Q

The tips of the stators are often joined by a blank to avoid energy losses and
reduce vibration

A

Shorid

36
Q

What does a shroud do?

A

Reduce energy loss and vibration

37
Q

What spins the compressor?

A

Turbinw

38
Q

Is a centrifugal or axial compressor cheaper?

A

Centrifugal

39
Q

Does a centrifugal or axial compressor have a higher compression ratio?

A

Axial (35:1)

40
Q

Is a centrifugal or axial compressor more efficient?

A

Axial compressor

41
Q

At what P does the highest pressure occur?

A

P3

42
Q

The Compressor will deliver high pressure (compressed) air into the mid-frame
diffuser (Px)

A

P3

43
Q

The diffuser also allows a separation of airflow into dilution air(cooling) (Xx%) and
combustion air (keeps fire alight) (Xx%);

A

80% 20%

44
Q

What do you need to check is increasing when you press the engine anti ice?

A

EGT

45
Q

Bleed Air is taken from several compressor stages to be used for various internal
engine tasks and externally to supply hot or high pressure air to aircraft systems
• But this blanks mass flow and increases temperature, hence:
• blanks power thrust
• blanks specific fuel consumption

A

Reduces mass flow reduces thrust increases fuel consumption

46
Q

X pressure air is used to ‘cool’ the turbine nozzle guide vanes, the turbine blades and the turbine discs
XP air is used to cool the accessories

A

High - low

Aircraft General Knowledge (42 decks)

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