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MOD 1 > Gas Turbine Engine > Flashcards

Gas Turbine Engine Flashcards

1
Q

Can an engine start by itself?

A

No

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2
Q

Is it safe to cut holes in a turbine blade to improve cooling?

A

No

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3
Q

Purpose of shroud at the tip of the turbine blades?

A

Help to minimise tip losses as well as provide a damper to prevent vibrations

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4
Q

Annular combustors suffer from?

A

Low rigidity

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5
Q

How to prevent engine stall due to choked flow?

A

Extract bleed air from the compressor stage after the stalled section.

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6
Q

Centrifugal Compressors have the following advantages compared to axial compressors? (5)

A
  • Simpler
  • More rugged
  • Cheaper to manufacture
  • Greater design flexibility
  • Less severe stall characteristics
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7
Q

Considerations for the design of Air Inlets include:? (5)

A
  • Noise attenuation
  • Radar attenuation (stealth)
  • Nozzle secondary airflow
  • Dust / Sand Particle Separation
  • Airflow bypass to assist in engine starting
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8
Q

Does an aircraft’s velocity affect the thrust produced by its engines?

A

Yes.

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9
Q

What is the purpose of flame holder?

A

To contains the flame of combustion and prevents flame out.

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10
Q

Is ice formation desirable?

A

Undesirable

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11
Q

Air starting of an engine involves the use of? (3)

A

an APU, a GPU or a Cartridge.

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12
Q

What is required for afterburner?

A

A variable-area exhaust nozzle

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13
Q

Turboshaft engines contains a?

A

Free turbine

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14
Q

[INFO]

Fnet = (Mass Flow Rate)(Vexit - Vinlet) + Aexit(Pexit - Pin) + …

A

Thus, you can accelerate a large mass through a small increase in velocity or a small mass through a large increase in velocity.

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15
Q

What is Mach number?

A

The ratio of the speed of a body to the speed of sound in the surrounding medium.

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16
Q

What is Brayton Cycle?

A

an idealised cycle with no energy losses to the surroundings. In actual cycles, the amount of energy lost is accounted for through process efficiency.

17
Q

What is the purpose of the exhaust nozzle?

A

To regulate back pressure on the turbine, accelerate exhaust gases to achieve desired jet velocity and deflect/reverse thrust.

18
Q

The exhaust nozzle is “used/not used” to increase backpressure?

A

not used

19
Q

Cooling methods in the turbine include? (4)

A
  • Convection
  • Impingement
  • Film
  • Transpiration
20
Q

Low Cycle Fatigue

A

failure typically occurs <100,000 cycles and is due to engine start/stop or throttle cycle.

21
Q

High Cycle Fatigue

A

failure typically occurs >100,000 cycles and is normally caused by vibratory stress.

22
Q

The Health & Usage Monitoring System (HUMS) is used for?

A

monitoring the health of the engine, which involves usage monitoring and flight data acquisition. It does not retrieve weather data or monitor air conditioning.

23
Q

Magnetic chip detectors are used for?

A

To catch ferrous particles in the oil system.

24
Q

High viscosity oil is used in turbo-propeller engines due to?

A

high mechanical loads involved.

25
Q

The Variable Divergent/Convergent Nozzle of the F100 engine is designed to?

A

significantly reduce the actuation forces necessary to reposition the nozzle.

26
Q

In the Axial Compressor, stator or rotor comes first?

A

stators come before rotors to direct air into the rotor.

27
Q

Air inlet ducts are generally rated by?

A

Their duct-pressure efficiency ratio and ram recovery point.

28
Q

Common Thermodynamic Processes (3)

A
  • Isobaric - Constantly Pressure
  • Isochoric - Constant Volume
  • Isentropic - Constant Entropy & Temperature
29
Q

Thermal Barrier Coating (TBC) is applied to stationary components in the combustion chamber to?

A

Reduce wall temperatures and gradients by reflecting gas radiation or providing a layer of insulation between hot gases and the wall.

30
Q

The disadvantage of using an airblast atomiser is?

A

at low air velocities, such as during start-up, the fuel droplets tend to be large, limiting the efficiency of the engine.

MOD 1 (12 decks)

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