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Module 15 > 15.12 > Flashcards

15.12 Flashcards

1
Q

What is the acceptable temperature range inside the engine?

A

800 to 1150 degrees

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2
Q

How do we keep engines to the correct temperature?

A

By cooling them with air

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3
Q

What is the hottest section of the engines?

A

Around the turbine

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4
Q

What does the secondary air do?

A

Cools the engine

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5
Q

Where do we get secondary air from?

A

Bleed air in the early stages of the compressor

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6
Q

What 4 things is secondary air used to cool?

A

Turbine disc
Vanes
Blades
Exhaust bearings

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7
Q

What does secondary air passing through the engine cool?

A

The combustion chamber liners

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8
Q

What is the most critical lubricating point due to the high temperatures?

A

Exhaust turbine bearing

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9
Q

As well as air cooling what method is also used to cool the bearings?

A

Oil cooling

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10
Q

Where are cooling inlets located?

A

The exterior of the engine

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11
Q

What cools the engine exterior and the nacelle?§

A

Passing fan air

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12
Q

What are the 3 zones?

A

Fan case compartment
Intermediate compressor case compartment
Core engine compartment

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13
Q

What are the 3 zones separated by?

A

A fireproof bulkhead or seal

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14
Q

What prevents the build-up of any harmful vapours?

A

Airflow

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15
Q

What is zone 1?

A

Area around the fan case that contains the accessory case and the ECC

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16
Q

What is zone 2 cooled by?

A

fan air from the upper part of the fan duct and is exhausted at the lower end back into the fan air stream

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17
Q

What is zone 3?

A

Area around high-pressure compressor to the turbine cases (also contains fuel and oil lines and other accessories)

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18
Q

In the majority of engines what 3 things utilise cooling air?

A

Compressor
Combustion
Turbine sections

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19
Q

What are the problems ice can cause?

A

Disruption of airflow
Ice can break off and damage the engine

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20
Q

What prevents formation of ice on the engine inlet cowls?

A

An anti-ice system

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21
Q

What temperature can ice form at and why?

A

5 degrees and below due to the chilling effect of high inlet velocities

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22
Q

What are anti-icing systems controlled by?

A

Automatically by a switch on the flight deck

23
Q

After heating the lip where does air exit through?

A

A grill on the nose cowl

24
Q

Can the flight crew select a manually select anti-ice if required?

A

Yes

25
Q

Where can an indication that the anti-icing valve is open be viewed?

A

On the engine parameters page

26
Q

What are the 5 internal subsystmes?

A

Compressor cooling
Combustion chamber coolings
Turbine disc cooling
Turbine Nozzle Guide Vanes (NGV) and blade cooling
Accessory section

27
Q

What is the temperature range at the rear stages of the compressor?

A

350 to 400 degrees

28
Q

What minimises the effect of heat on the compressor?

A

The compressor rotor cavity is provided with cooling air from an intermediate compressor stage

29
Q

What does the combustion chamber consist of?

A

An outer casing with a perforated inner liner

30
Q

That is the air in the combustion chamber divided into?

A

Primary and Secondary paths

31
Q

How much of the air is primary air?

A

20% - 30%

32
Q

How much of the air is secondary air?

A

70% - 80%

33
Q

Where does secondary air go?

A

To the combusts periphery at several hundred m/s

34
Q

What does secondary air form?

A

A cooling air blanket on both sides of the inner liner

35
Q

What does secondary air ensure about the flame?

A

It doesn’t contact the liner

36
Q

What are the 2 ways cooling takes place in the combustion chamber?

A

Cooling air removes heat from the combustion liner
Colling air creates a film which acts as a thermal barrier between the hot gases and the combustion line

37
Q

What temperature do the turbine blades and vane operate at?

A

300 to 400 degrees

38
Q

What is the most common method to cool the turbine components?

A

Engine bleed air

39
Q

What is done to limit the effects of temperature variations of the turbine dic?

A

Cooling sir is directed over each side of the disc

40
Q

What is done to increase the life expectancy of the turbine NGV and blades?

A

They are cooled by compressor air (guide vanes are cooling by compressor discharge air)

41
Q

What air cools engine accessories and electrical generators?

A

Air from intakes in the fan cowlings or from the compressor

42
Q

How is oil cooled?

A

By an air-cooled oil cooler where fan air is used

43
Q

What air is used for the sealing of the engine bearing chambers?

A

LP compressor bleed air

44
Q

What stops oil from escaping out of the bearing chamber?

A

Pressurised air acting on the air and oil seals

45
Q

Where is air that enters the bearing compartment vented?

A

Overboard through the hollow N1 rotor shaft

46
Q

What is a secondary function of the compressor?

A

To supply air to the various systems on the aircraft

47
Q

What stages of the compressor can bled air be taken off?

A

Any

48
Q

What are 4 examples of where bleed air is used?

A

Cabin pressurisation, heating and cooling
De-icing and anti-icing equipment
Pneumatic starting of engines
Auxiliary Drive Units (ADU)

49
Q

Where does the external cooling system cool?

A

External areas between the cowling and the engine case

50
Q

What are the 2 sections that the areas below the engine cowling are divided into?

A

The fan compartment
The core compartment

51
Q

What doe the external cooling system ensure?

A

That the engine case and all fan components and core compartments are sufficiently cooled

52
Q

What does the external cooling system also prevent?

A

Flammable vapours from collecting in the engine compartments

53
Q

What are the fan and cor compartments separated by and what does this mean in terms of cooling?

A

Bulkheads and fir seals meaning they are cooled and vented separately

54
Q
A

Module 15 (18 decks)

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