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Resource Group Mod 15 2024 > 15.12 Air Systems > Flashcards

15.12 Air Systems Flashcards

1
Q

A large vloume of air cools the hot sections of the engine, to what acceptable temperature range?

A

800 - 1150 degrees C

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2
Q

What ‘type’ of air is used to cool the combustion chamber liners?

A

Secondary air.

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3
Q

What are considered the primary zones of the engine? (3)

A
  • Fan case compartment.
  • Intermediate compressor case compartment.
  • Core engine compartment.
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4
Q

What is included in the Zone 1 area?

A

The area around the fan case, containing the accessory case and EEC.

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5
Q

How is the zone 1 area vented and cooled?

A

Ram air enters through and inlet tube in the nose cowl. It exits through a vented panel in the RHS engine fan cowling.

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6
Q

What does the Zone 1 area have to protect against overpressure?

A

Pressure relief door.

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7
Q

What is included in the Zone 2 area?

A

Fuel and oil lines.

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8
Q

How is the zone 2 area cooled?

A

Cooled by fan air from upper fan duct, and exhausted out at the lower end to rejoin the fan-air stream.

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9
Q

What does the zone 3 area cover?

A

The area around the HP compressor to turbine cases. Also contains fuel/oil lines and other accessories.

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10
Q

How is the Zone 3 area cooled?

A

Air enters the from the outlet of the pre-cooler, and exits through the aft edge of the thrust reverser inner wall and turbine exhaust sleeve.

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11
Q

At what temperature can ice form on the inlet?

A

Any temperature up to 5 degrees C.

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12
Q

Is the anti-icing system normally controlled automatically or manually?

A

Normally controlled automatically.

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13
Q

How does the anti-ice system operate automatically?

A

The system activates when icing condtions are detected.

The system opens a bleed valve, that bleeds hot air from the compressor.

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14
Q

What areas of the engine are fed with hot bleed air for anti-icing? (3)

A
  • The inlet leading edge.
  • Nose dome.
  • Inlet guide vanes.
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15
Q

Where does the bleed air that’s used to heat the inlet, exit the aircraft?

A

Via grills in the nose cowling.

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16
Q

What is the approximate temperature of the aft section of the compressor?

A

350-450 degrees C.

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17
Q

How is the aft stage of the compressor cooled?

A

Rotor cavity is provided with air from the intermediate compressor stage, which is a bit cooler.

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18
Q

What type of airflow cools the combustion chamber inner liner?

A

The secondary airflow.

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19
Q

What 2 things does the secondary airflow do to help keep the inner liner cool?

A
  • Forms a cooling air blanket on both sides of the liner, acting as a thermal barrier.
  • Removes heat directly.
20
Q

What feature of the combustion chamber’s outer-casing inner liner, also assists with cooling?

A

The inner liner is perforated.

21
Q

How does the secondary airflow assist with flame propagation?

A

It keeps the flame straight, preventing it from contacting the inner liner

22
Q

What is the main benefit of using cooling systems on turbines?

A

It allows the turbine to operate at 300-400 degrees C above the limits of their metal alloys.

23
Q

What’s the most common method used to cool the turbine section?

A

Bleed air.

24
Q

What is usually at a higher temperature on the turbine disc, the rim of the disk or the centre of the disk?

A

The rim of the disc.

25
Q

How is the turbine disc cooled, generally?

A

Cooling air is directed over each side of the disc.

26
Q

How is the HP turbine disc cooled?

A

By compressor discharge air (P3).

27
Q

How is the LP turbine disc cooled?

A

By intermediate compressor stage air.

28
Q

What are the two methods of turbine blade cooling?

A
  • The disc acts as a heat-sink to cool the blades.
  • The disc has holes drilled into the front face, that receive cooling airflow that flows up into the blades through holes in the blade roots.
29
Q

How are Nozzle Guide Vanes cooled?

A

By compressor discharge air (P3).

30
Q

What cools accessory units in-flight?

A

Atmospheric air.

31
Q

How are accessory units cooled on the ground?

A

Compressor air passes through nozzles in cooling air outlet duct at high velocity, reducing the pressure in this area that draws-in atmospheric air.

32
Q

What air is used as the cooling medium in air-cooled oil coolers?

A

Fan-air.

33
Q

What air is used for sealing engine bearing chambers?

A

LP compressor bleed air.

34
Q

What creates an additional sealing effect on air seals and oil seals?

A

Pressurised air.

35
Q

How is the air, that enters bearing compartments, eventually vented overboard?

A

Through the hollow N1 shaft.

36
Q

What systems is bleed air used for? (4)

A

-Cabin pressurisation, heating, and cooling.
- De-icing and Anti-icing.
- Pneumatic engine starting.
- Auxillary drive units.

37
Q

Where can bleed air be ‘tapped off’ from in the compressor section?

A

Any compressor stage, dependent on the pressure and temperature of the bleed air required by the receiving system.

38
Q

What gives the highest pressure and temperature of bleed air?

A

HP compressor.

39
Q

Underneath the fan cowls, what two compartments is the engine divided into?

A
  • Fan compartment.
  • Core compartment.
40
Q

As each compartment is seperated by bulkheads and fireseals, how is each compartment cooled and vented?

A

Seperately.

41
Q

What specifically-named type of inlets scoop-up ram air for cooling?

A

NACA ducts/inlets.

42
Q

What is a Bowed-rotor condition?

A

Engine bending due to different thermal expansion rates between the upper and lower zones.

43
Q

What are the effects of a Bowed-rotor condition?

A
  • Distortion can cause rotors to contact the stator cases.
  • High vibration on engine start.
  • Hung-up engine start.
44
Q

How is Bowed-rotor condition prevented?

A

By waiting a specified minimum time between engine shutdown and successive start.

45
Q

What’s can cause a critical Bowed-rotor condition?

A

The lower part of the engine becomes colder than the upper part of the engine.

Resource Group Mod 15 2024 (13 decks)

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