Module 15.5 Combustion Section

Question 1

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

Answer 1

It raises it.

Question 2

Where is a large part of the energy released required?

Answer 2

At the turbine or turbine stages to drive the compressor.

Question 3

What does the combustion process release?

Answer 3

Energy contained in the air/fuel mixture.

Question 4

Combustion should happen with…

Answer 4

Minimum pressure loss in the combustion chamber.

Question 5

What are the two main components of the combustion chamber?

Answer 5

The combustion chamber casing.

The flame tube found inside the casing.

Question 6

The casing can be split into what?

Answer 6

Inner and an outer casing.

Question 7

What is the combustion chamber casing?

Answer 7

The outer shield of the combustion section.

Question 8

What does the combustion chamber casing do?

Answer 8

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

Question 9

What does the flame tube do?

Answer 9

Controls and guides the flame.

Question 10

Describe the combustion chamber process?

Answer 10

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.

Question 11

When is the ignition switched off?

Answer 11

After the combustion has been started.

Question 12

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

Answer 12

15 parts of air for 1 part of fuel.

Question 13

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

Answer 13

The primary airflow

The secondary airflow

Question 14

What is the primary air flow used for?

Answer 14

For the combustion process.

Question 15

What percentage of the airflow from the compressor is primary?

Answer 15

20% to 30%

Question 16

What is done with the secondary airflow?

Answer 16

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

Question 17

List the three combustion chamber types?

Answer 17

Can-type

Can-annular

Annular

Question 18

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

Answer 18

Old gas turbine engines with centrifugal compressors.

Question 19

What is a can-type combustion chamber?

Answer 19

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

Question 20

What is a can-annular combustion chamber?

Answer 20

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

Question 21

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

Answer 21

Annular combustion chamber

Question 22

How many flame tubes does an annular combustion chamber have?

Answer 22

One

Question 23

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

Answer 23

Dome

Inner liner

Outer liner

Question 24

What are the fuel nozzles surrounded by?

Answer 24

Swirl vanes

Question 25

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

Answer 25

Because of the airflow direction in the flame tube.

Question 26

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

Answer 26

Two

Question 27

A typical annular combustion chamber consist of what three things?

Answer 27

Combustion case Flame tube External components

Question 28

What does the combustion case consist of?

Answer 28

Outer wall Inner wall A diffuser

Question 29

What does the dome section of the flame tube do?

Answer 29

Connects the inner liner with the outer liner.

Question 30

What does the dome section of the flame tube house?

Answer 30

The swirlers with swirl vanes.

Question 31

What does the secondary airflow do?

Answer 31

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

Question 32

The secondary airflow enters the flame tube through what?

Answer 32

Holes in the liner.

Question 33

What is a rich mixture?

Answer 33

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.

Question 34

What is a lean mixture?

Answer 34

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

Question 35

What does a lean mixture cause in terms of emissions?

Answer 35

Less pollution

Question 36

What does a rich mixture cause in terms of emissions?

Answer 36

A build-up of carbon monoxide.

Question 37

What compressor type would a can-type compressor be used with?

Answer 37

Centrifugal compressor

Question 38

Where in the combustion case are the igniters found?

Answer 38

Behind the nozzles on the lower half.

Question 39

What kind of combustion chamber is used to decrease emissions?

Answer 39

Dual dome combustion chambers.