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CAA Module 15 > Module 15.5 Combustion Section > Flashcards

Module 15.5 Combustion Section Flashcards

1
Q

What does the combustion section do to the temperature of air?

A

It raises it.

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2
Q

Where is a large part of the energy released required?

A

At the turbine or turbine stages to drive the compressor.

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3
Q

What does the combustion process release?

A

Energy contained in the air/fuel mixture.

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4
Q

Combustion should happen with…

A

Minimum pressure loss in the combustion chamber.

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5
Q

What are the two main components of the combustion chamber?

A

The combustion chamber casing.

The flame tube found inside the casing.

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6
Q

The casing can be split into what?

A

Inner and an outer casing.

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7
Q

What is the combustion chamber casing?

A

The outer shield of the combustion section.

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8
Q

What does the combustion chamber casing do?

A

Takes the air pressure loads and protects the internal and external engine parts from the hot combustion gases.

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9
Q

What does the flame tube do?

A

Controls and guides the flame.

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10
Q

Describe the combustion chamber process?

A

Compressed air enters the combustion chamber. Fuel nozzles/injectors spray the fuel into the centre of this airflow.

The fuel vaporises and mixes with the airflow and the mix is electrically ignited by an igniter plug.

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11
Q

When is the ignition switched off?

A

After the combustion has been started.

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12
Q

For complete combustion of a kerosene-air mixture, what air:fuel ratio is required?

A

15 parts of air for 1 part of fuel.

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13
Q

Airflow coming from the compressor is split into what two parts?

A

The primary airflow

The secondary airflow

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14
Q

What is the primary air flow used for?

A

For the combustion process.

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15
Q

What percentage of the airflow from the compressor is primary?

A

20% to 30%

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16
Q

What is done with the secondary airflow?

A

It bypasses the primary combustion zone and mixes with the hot gas in the dilution zone

17
Q

List the three combustion chamber types?

A

Can-type

Can-annular

Annular

18
Q

Where engines can can-type combustion changes be found on?

A

Old gas turbine engines with centrifugal compressors.

19
Q

What is a can-type combustion chamber?

A

One with multiple-can combustion chambers that are installed around the engine combustion section.

20
Q

What is a can-annular combustion chamber?

A

A set of flame tubes installed around the combustor section. All the flame tubes have a common outer casing and inner casing.

21
Q

What type of combustion chamber is most commonly used on modern jet gas turbine engines?

A

Annular combustion chamber

22
Q

How many flame tubes does an annular combustion chamber have?

A

One

23
Q

What are the three major parts of the annular combustion chamber?

A

Dome

Inner liner

Outer liner

24
Q

What are the fuel nozzles surrounded by?

A

Swirl vanes

25
Q

Why is the annular combustion chamber called the reverse flow combustion chamber?

A

Because of the airflow direction in the flame tube.

26
Q

How many igniter plugs are installed in the combustor case of an engine?

A

Two

27
Q

A typical annular combustion chamber consist of what three things?

A

Combustion case

Flame tube

External components

28
Q

What does the combustion case consist of?

A

Outer wall

Inner wall

A diffuser

29
Q

What are the three main components of the flame tube?

A

Outer and inner liner

Outer and inner cowl

Dome

30
Q

What does the dome section of the flame tube do?

A

Connects the inner liner with the outer liner.

31
Q

What does the dome section of the flame tube house?

A

The swirlers with swirl vanes.

32
Q

What does the secondary airflow do?

A

Forms a cooling film on the inner surface of the liners, which helps to protect the liner from the intense heat (film cooling).

33
Q

The secondary airflow enters the flame tube through what?

A

Holes in the liner.

34
Q

What is a rich mixture?

A

A mixture where there is too much fuel for the primary air in the combustion chamber.

In this condition, some of the fuel cannot be burned and is released into the exhaust.

35
Q

What is a lean mixture?

A

Where there is insufficient fuel available in the combustion chamber. This causes the flame to go out?

36
Q

What does a lean mixture cause in terms of emissions?

A

Less pollution

37
Q

What does a rich mixture cause in terms of emissions?

A

A build-up of carbon monoxide.

CAA Module 15 (18 decks)

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