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M15✅ > 15.5 COMBUSTION SECTION👌🏼 > Flashcards

15.5 COMBUSTION SECTION👌🏼 Flashcards

1
Q

Simply explain combustion process

A
  • raises temperature of air
  • releases energy contained in air/fuel mixture
  • which drives turbine and compressor
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2
Q

What are the 2 main components in a combustion chamber

A
  • combustion chamber casing
  • flame tube found inside casing
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3
Q

What is the fuel-air mixture electrically ignited by

A
  • igniter plug
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4
Q

After the combustion has been started what occurs to the ignition

A

It is switched off

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5
Q

What 2 primary conditions are necessary for correct and safe combustion

A
  • ratio of air and fuel must be correct
  • air velocity must be slow to ensure complete combustion inside combustion chamber
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6
Q

What is the complete ratio for complete combustion

A
  • 15 parts of air, 1 part of fuel
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7
Q

Airflow are split into 2 parts

A
  • primary airflow
  • secondary airflow
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8
Q

20% to 30% of the airflow from the compressor

A
  • primary airflow
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9
Q

What are the 3 types of combustion chambers used on gas turbine engines

A
  • can-type combustion chamber
  • can-annular combustion chamber
  • annular combustion chamber
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10
Q

Explain Can-type combustion chambers

A
  • found on old gas turbine engines with centrifugal compressors
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11
Q

Advantage of can-type combustion chambers

A
  • simple in design
  • very good structural strength
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12
Q

Disadvantage of can-type combustion chambers

A
  • heavy
  • require a lot of space
    -need complicating air supply ducts from compressor
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13
Q

Explain can-annular combustion chambers

A
  • set of flame tubes installed around combuster section
  • all flame tubes have common outer casing and inner casing
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14
Q

Advantages of can-annular combustion chamber

A
  • smaller, lighter than multiple can-type combustion chamber
    P
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15
Q

Disadvantage of can-annular combustion chamber

A
  • high aerodynamic losses
  • ignition from one flame tube to another is difficult
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16
Q

Which combustion chamber is used on modern gas turbine engines

A
  • annular combustion chamber
17
Q

How many flame tubes does the annular combustion chamber have

A

1

18
Q

In a annular combustion chamber what is the flame tube supported by

A
  • inner and outer combustion chamber casing
19
Q

What are the 3 major parts of a combustion chamber casing

A
  • dome
  • inner liner
  • outer liner
20
Q

Advantages of annular combustion chamber

A
  • Smaller, lighter
  • better efficiency
  • combustion is smokeless
21
Q

Disadvantage of annular combustion

A
  • expensive to make
  • removal is difficult and time consuming
22
Q

What does the dome have openings for

A
  • fuel nozzles
23
Q

What are the fuel nozzles surrounded by

A

Swirl vanes

24
Q

Annular combustion chamber construction

A
  • combustion case
  • flame tube
  • external components (fitted on outer wall)
25
Q

What is included in the combustion case assembly

A
  • outer wall
  • inner wall
  • diffuser
26
Q

Explain Flame tube cooling

A

Done by secondary airflow, forms a cooling film

27
Q

What is a more sophisticated method of film cooling

A
  • transpiration cooling (requires less air for cooling the flame tube liners)
28
Q

How is secondary airflow entered in the flame tube

A
  • radial holes in the liner
29
Q

Explain rich mixture

A

-too much fuel for primary air in combustion chamber
- some fuel therefore cannot be burnt and released into the exhaust

30
Q

When does lean mixture occurs

A

If insufficient fuel is available in the combustion chamber

31
Q

What occurs to the remaining airflow from compressor (secondary airflow)

A
  • bypasses and mixes with hot gas in the dilution zone
32
Q

Where is the flame stabilised. PRIMARY ZONE OR SECONDARY ZONE

A

primary zone

M15✅ (16 decks)

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