P Gas Turbine Compressor Flashcards

1
Q

What are the 2 types of compressor?

A
  • Axial flow

- Centrifugal

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2
Q

How can a centrifugal compressor stall?

A

Centrifugal compressors cannot stall

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3
Q

What’s the max compression ratio of a centrifugal compressor?

A

4.5:1

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4
Q

What is an axial flow compressor made up of?

A

Series of rotor blades accelerate the air towards stationary stator blades

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5
Q

What does a compressor rotor do to P, V and T?

A

P - increases
V - increases
T - increases

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6
Q

What does a compressor stator do to P, V and T?

A

P - static pressure increases
V - reduces
T - constant

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7
Q

What is the name for when one stage stalls, causing others to stall?

A

Surge

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8
Q

What is the name for complete reversal of airflow through the compressor?

A

Deep surge

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9
Q

What can trigger blade stall?

A
  • Damage
  • Ice
  • Extreme angles of incidence
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10
Q

What is the consequence of compressor stall?

A

Reduced thrust

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11
Q

What are the 4 symptoms of compressor stall?

A
  • High gas temperature (EGT)
  • Reduced thrust
  • Rumbling or banging from the compressor
  • Fluctuating RPM and fuel flow
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12
Q

What can over fueling cause?

A

Surge, by creating excessive pressure in the combustor

Mostly eliminated by modern FCU’s

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13
Q

What are variable inlet guide vanes (VIGV)?

A

Vanes in the inlet which adjust their angle to ensure air is directed onto the 1st stage at the correct angle

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14
Q

What are variable stator vanes?

A

Ensure the optimum angle of attack for each rotor for each stage

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15
Q

What is the purpose of inter stage bleed valves?

A

Vent pressure during start to improve axial flow across the compressor, reduces load on the compressor

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16
Q

Why are rotor blades fitted loosely?

A

So that they take up a position of least stress

17
Q

What is the compression ration of an axial flow compressor?

A

35:1

18
Q

Where is bleed air taken from?

A

Jut before the combustor after the compressors

19
Q

What does the diffuser do?

A

Allows a separation of airflow into dilution air (80%) and combustion air (20%)

20
Q

What are the side effects of taking bleed air from the engine?

A

Reduced power thrust

Increases specific fuel consumption

21
Q

What are the main functions of the internal bleed air system?

A
  • Internal engine and accessory cooling
  • Bearing chamber sealing
  • Prevention of hot gas ingestion into turbine disc cavities
  • Engine anti icing