M15.5

Question 1

What’s the purpose of the combustion chamber?

Answer 1

To produce a hot stream of gas for the turbines and jet nozzle

Question 2

The combustion chamber must be…

Answer 2

Small and light
Have a cooling system
A high operating lifetime

Question 3

Combustion must have a minimum amount of what?

Answer 3

Pressure loss

Question 4

What components comprise the combustion section?

Answer 4

Casing
Flame tube

Question 5

What does the combustion chamber casing do?

Answer 5

Take air pressure loads
Protects internal and external parts from hot combustion gasses

Question 6

What does the combustion chamber housing do?

Answer 6

Give support to:
Flame tube
Fuel nozzles
Igniter plugs

Question 7

What’s the purpose of the flame tube?

Answer 7

It controls and guides the flame

Question 8

How is the flame tube protected from the extreme temps of combustion

Answer 8

By using secondary airflow

Question 9

What will hot spots in the flame tube indicate?

Answer 9

Cooling airflow is not correct or the ceramic lining is damaged

Question 10

What do fuel nozzles do in the combustion chamber?

Answer 10

Spray fuel into the centre of the airflow

Question 11

How is the fuel and air mixture ignited?

Answer 11

Electrically with a igniter plug

Question 12

After combustion has started what happens with ignition?

Answer 12

Turned off

Question 13

What are the 2 primary conditions for safe combustion?

Answer 13

The ratio of fuel to air must be kept correct
The airs velocity must be slowed down enough to ensure combustion is completed

Question 14

What percentage of air from the compressor is used for combustion?

Answer 14

20 - 30%

Question 15

What percentage of air from the compressor is used for cooling?

Answer 15

70 - 80%

Question 16

What is the required fuel to air ratio for combustion?

Answer 16

1:15
Fuel:air

Question 17

What is the primary zone in the combustion chamber?

Answer 17

Where the flame stabilises

Question 18

What is the secondary air used for in the combustion chamber?

Answer 18

Keep the flame away from the flame tube walls

Question 19

What is the secondary zone also known as?

Answer 19

The dilution zone

Question 20

What cooling methods are used on combustion liners?

Answer 20

Film cooling and transpiration cooling

Question 21

What are the 3 types of combustion chambers?

Answer 21

Can- type
Can-annular
Annular

Question 22

Where are can-type combustion chambers usually found?

Answer 22

Old GTE’s with centrifugal compressors

Question 23

What are the advantages of a can-type combustion chamber?

Answer 23

Individually removable
Good structural strength
Simple design

Question 24

What are the disadvantages of a can-type combustion chamber?

Answer 24

Ignition difficulties
Aerodynamic loss
Large and heavy

Question 25

What are the advantages of a can-annular combination chamber?

Answer 25

Structural strength Simple air supply Dimension and weight

Question 26

What are the disadvantages of a can-annular combustion chamber?

Answer 26

Ignition difficulties Aerodynamic loss

Question 27

What are the advantages of a annular combustion chamber?

Answer 27

Thermal load distribution Flame propagation Complete combustion Efficient Dimension and weight

Question 28

What are the disadvantages of a annular combustion chamber?

Answer 28

Maintenance costs Manufacturing costs

Question 29

What type of combustion chamber is most common on modern a/c?

Answer 29

Annular type

Question 30

The annular combustion chamber case carries structural loads between what?

Answer 30

Compressor case Turbine case

Question 31

What does the flame tube do?

Answer 31

Stabilises and controls the flame

Question 32

Why is a flame tube only secured at one end?

Answer 32

To allow for thermal expansion

Question 33

What is the purpose of the diffuser?

Answer 33

To reduce velocity of airflow coming from the compressor

Question 34

The combustion case assembly is made up of what?

Answer 34

Outer wall Inner wall Diffuser

Question 35

Why is the rear part of the inner wall on the combustion case removable?

Answer 35

To allow for access to the flame tube

Question 36

What’s the purpose of the combustion case?

Answer 36

Part of the load carrying structure of the engine, protects engine parts from excess heat and provides mounts for the combustion chambers components

Question 37

How many igniter plugs are there usually in the combustion case?

Answer 37

2

Question 38

What’s fitted to the combustion case for Maintenance?

Answer 38

Borescope ports

Question 39

What does the compressor rear frame house?

Answer 39

Bearings for high pressure rotor

Question 40

What does the dome section of the flame tube do?

Answer 40

Connects inner and outer liners Also houses swillers and swill vanes

Question 41

What is the outer liner of the flame tube attached to?

Answer 41

Inner surface of the outer wall in a axial direction only by a recess

Question 42

How is the inner liner support for the flame tube attached?

Answer 42

Bolted to inner wall of combustion case

Question 43

How is the dome centred in the combustion case?

Answer 43

By mounting pins

Question 44

How does primary airflow enter the flame tube?

Answer 44

Through swill vanes

Question 45

How does secondary airflow enter the flame tube?

Answer 45

Passes the cowl and enters via liners

Question 46

What are the 3 types of film cooling?

Answer 46

Machined cooling Corrugated strip cooling Splash cooling strip

Question 47

What’s the advantage and disadvantage of transpiration cooling?

Answer 47

Requires less air but is Sophisticated

Question 48

What is the inner surface of the flame tube covered with in the transpiration cooling method?

Answer 48

Detachable tiles called liner segments

Question 49

How do liner segments allow for cooling?

Answer 49

By allowing air to flow between the segments and liner