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M15 > M15.05 Combustion > Flashcards

M15.05 Combustion Flashcards

1
Q

What is the main function of the combustion chamber?

A

Produce hot stream of gas for turbines and jet nozzles

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2
Q

Briefly How does it produce the stream of hot gas?

A

By continuous combustion of fuel and air mixture

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3
Q

What 3 things ensure a safe and efficient combustion?

A

. Safe ignition
. No un burned fuel - combustion complete
. Stable combustion

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4
Q

What are the two main components of the combustion chamber?

A

. Combustion chamber casing - outer
. Flame tube - inside casing

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5
Q

The hosing of the combustion also does what??

A

Supports the flame tube, fuel nozzles and igniter plugs

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6
Q

What is the purpose of the flame tube??

A

Controls and guides the flame
It’s made of many segments with lots of holes and slots

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7
Q

What’s the basic combustion process?

A

. Compressed air into combustion chamber
. Fuel nozzles spray fuel into centre of airflow
. Fuel vaporises and mixes with airflow
. Then fuel/air is electrically ignited by igniter plug
. After combustion started the igniter is switched off
. Then it’s a continuous cycle

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8
Q

What is needed for safe and correct combustion?

A

. Ratio of air to fuel mist be correct
. Air velocity must be slow enough to ensure combustion is done in chamber

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9
Q

What’s the ratio of ketosene: air mixture??

A

15:1

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10
Q

Airflow form the compressor is split into what two parts?

A

. Primary airflow
. Secondary airflow

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11
Q

What is primary airflow used for and what % is used??

A

. Used for the combustion oricess
. 20 - 30%

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12
Q

What is secondary airflow used for and what % is used??

A

. Used for cooling (bypasses primary combustion zone, and mixes with hot gas in dilution zone)
. keeping the flame away from flame walls
. 70-80%

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13
Q

What is the other name for secondary airflow?

A

Bypass airflow

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14
Q

Why does the secondary air needs to keep the flame away from the flame walls?

A

Because the temperature in the centre if the flame reaches 2000 degrees

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15
Q

What are the 3 types of combustion chambers??

A

. Can-type combustion chamber
. Can - annular combustion chamber
. Annular combustion chamber

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16
Q

What temperature can the flame centre reach?

A

2000 degrees c

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17
Q

How does secondary airflow reach the dilation zone?

A

Through dilution air holes

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18
Q

Where are can- type combustion chambers found?

A

On old gas turbine engines with centrifugal compressors

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19
Q

How does a can- type combustion chamber work?

A

Multiple installed around the engine and connect to each other by interconnection tubes which allow ignition from each other

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20
Q

What’s the main advatange of the can- type combustion chamber?

A

Very simple deign

21
Q

What’s the main negative of a can- type combustion chamber?

A

Heavy and need a lot of space

22
Q

How does a can -annular type combustion chamber works?

A

Has a set of flame tubes installed around the combustion section. With all the flame tubes having a common inner and outer casing

23
Q

What are a few advatanges of a can annular combustion chambers.

A

. Smaller and lighter
. Not complicated

24
Q

What are 2 disadvantages of a can annular type combustion chamber?

A

. Difficult ignition
. Aerodynamic loss

25
Q

Where are annular combustion chambers most used??

A

. On modern gas turbine engines

26
Q

How does an annular combustion chamber work?

A

Only has one annular flame tube which is supported by and inner and outer combustion chamber casing

27
Q

What are three main parts of combustion chamber?

A

. The dome
. Inner lining
. Outer lining

28
Q

The flame tubes on an annular are often called what?

A

Combustion chamber

29
Q

What are the advantages of an annular combustion chamber?

A

. Smaller and lighter
. Better efficiency
. Better thermal load distribution
. Very long service life

30
Q

What are some disadvantages of the annular type annular combustion chamber?

A

. Expensive
. Removal is very hard

31
Q

What is the purpose of the of a flame tube?

A

It stabilises the flame during combustion

32
Q

What are the external components of a combustion chamber?

A

. Fuel nozzles
. Igniter plugs

33
Q

2hat are the 3 main parts of the combustion case??

A

. Inner wall
. Outer wall
. Diffuser

34
Q

What is the last stator valve of HP compressor??

A

Exit guide vanes

35
Q

Stator vanes of the last stage of the HP compressor are known as??

A

Guide vanes

36
Q

The outer wall of the combustion chamber case has opening for?

A

. Bleed air from HP compressor for pneumatics

37
Q

The openings for fuel nozzles and igniter plugs used for?

A

Used for borescope inspections of flame tube

38
Q

What are the main components of the flame tube assembly?

A

. Outer and inner liner
. Outer and inner cowl
. Dome

39
Q

What else does the dome house?

A

Swirl vanes

40
Q

How is the flame tube fixed?

A

Fixed in all three dimensions at the aft end

41
Q

Another type of flame tube is made by?

A

Two pieces

42
Q

How does primary airflow enter the flame tube??

A

Through swirl vanes

43
Q

How does secondary airflow enter the flame tube??

A

Passes the cowl and enters the flame tube through liners

44
Q

What is the cooling method of secondary airflow called??

A

Film cooling method

45
Q

Why do we have film cooling?

A

To protect the liners inside from the intense heat of combustion gases

46
Q

What are the three types of film cooling methods??

A

. Corrugated station cooling
. Machined cooling ring
. Splash cooling strip

47
Q

What is the newest/ most sophisticated method of cooling?

A

. Transpiration
Which requires less aid for cooling the flame tube lines

48
Q

What is another method to protect materials against heat??

A

. Thin coating of ceramic materials on the inner surface if the flame tube

M15 (10 decks)

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