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M15 New > 15.5 > Flashcards

15.5 Flashcards

1
Q

Important requirement of combustion

A

It must be complete , no unburnt fuel leaves the combustion chamber

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2
Q

What important about combustion chamber outlet

A

Equal temperature distribution, especially at first turbine stage

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3
Q

3 requirements of combustion chamber

A

Small and light

Dependable cooling system

High operating lifetime

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4
Q

Why do we need a small and light chamber

A

To save weight

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5
Q

What’s the problem with replacing engine components in the combustion chamber

A

It’s very time consuming

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6
Q

2 parts of combustion chamber

A

Casing (can be inner and outer)

Flame tube

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7
Q

What does the casing do

A

Outer shield that takes air pressure loads and protects external engine parts

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8
Q

What does the housing support

A

Flame tube and other combustion chamber components (fuel nozzle and igniter plugs)

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9
Q

What does the flame tube do

A

Control and guides the flame

Made of segments and had lots of holes and slots

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10
Q

Conditions for correct and safe combustion

A

Correct fuel to air ratio

Air velocity slow enough to make sure combustion is completed inside the chamber

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11
Q

Kerosene air fuel mix ratio

A

15 parts air 1 part fuel

15:1

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12
Q

What air is used for combustion process

A

Primary

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13
Q

What % of air is primary from the compressor

A

20-30%

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14
Q

What part of the chamber does the flame stabilise

A

Primary zone

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15
Q

3 types of combustion chambers

A

Can-type

Can-annular

Annular

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16
Q

Where are can-type combustion chambers used

A

Old gas turbines with centrifugal compressors

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17
Q

Advantage of can-type

A

Simple and goodstructural strength

Removed and replaced individually

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18
Q

Disadvantage of can-type

A

Difficult ignition from one chamber to another

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19
Q

Advantage on can-annular

A

Smaller and lighter than a similar multiple can-type combustion chamber

20
Q

Disadvantage of can-annular

A

Poor ignition from flame tubes and aerodynamic loses are high

21
Q

What’s the most used combustion chamber construction

A

Annular

22
Q

How does annular combustion chamber work

A

One annular flame tubes supported by inner and outer chamber casing

23
Q

3 parts of annular construction

A

Dome

Inner liner

Outer liner

24
Q

Why is annular a reverse flow combustion chamber

A

Airflow direction in the flame tube

25
Q

Disadvantage of annular

A

Expensive to make and removal is very difficult and time consuming

26
Q

Annular construction

A

Combustion case

Flame tube

External components fitted to the outer wall

27
Q

Annular combustion case construction

A

Outer wall

Inner wall

Diffuser

28
Q

Why is the inner wall removable and what does it attach

A

Removable so the flame tube can be installed

Attaches the nozzle guide vanes HPT and support flame tube

29
Q

What are stator vanes also known as

A

Exit guide vanes

30
Q

How many igniter plugs are installed

A

2

31
Q

Flame tube components

A

Outer and inner liner

Outer and inner cowl

Dome

32
Q

How does primary air enter the flame tube

A

Swirl vanes

33
Q

How does secondary air enter the flame tube

A

Passed the cowl and enters through liners

34
Q

What is film cooling

A

Secondary airflow forms a film to protect the liner from intense heat of combustion gases

35
Q

What is transpiration cooling

A

Inner surface of flame tubes liner covered with detachable tiles

36
Q

How does secondary air get into the liner

A

Radial holes

37
Q

What does excessive fuel cause a build up of

A

Carbon monoxide

38
Q

What does an increase in combustion temperature have an effect on

A

Decrease carbon monoxide and hydrocarbon emissions

Increase nitrogen oxide emissions and vice versa

39
Q

What’s a benefit of dual dome combustion chambers

A

Shorter then standard chambers

40
Q

What’s the advantage of shorter combustion chambers

A

Reduces time the exhaust gas is in the hot area and build up of nitrogen oxides

41
Q

What’s a rich mix

A

Too much fuel for primary air in the combustion chamber

42
Q

What’s a lean mix

A

Not enough fuel for the combustion chamber

43
Q

What does the dome do

A

Connect the inner and outer liner

44
Q

What is the outer liner and dome made in

A

One piece

45
Q

How is the dome centred

A

By mounting pins

46
Q

Where is the inner liner bolted to

A

Inner flange of HPT nozzle guide vanes

M15 New (18 decks)

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