15.5 Combustion Section (Level 1, 3 Questions)

Question 1

What is the primary purpose of the combustion section in an engine?
A. To raise the temperature of the air and release energy from the air/fuel mixture
B. To cool the air before it enters the turbine stages
C. To reduce the energy needed to drive the compressor

Answer 1

A. To raise the temperature of the air and release energy from the air/fuel mixture

Question 2

What ensures the safe ignition of the fuel-air mixture for the safe and efficient operation of the engine?
A. The release of unburnt fuel
B. The combustion chamber design for both ground and flight operations
C. The combustion shutdown system

Answer 2

B. The combustion chamber design for both ground and flight operations

Question 3

What is one requirement of the combustion chamber for the safe and efficient operation of the engine?
A. To stop combustion during high-speed flight
B. To give stable combustion in all operating conditions
C. To release unburnt fuel into the atmosphere

Answer 3

B. To give stable combustion in all operating conditions

Question 4

Why must combustion be complete in the combustion chamber for the safe and efficient operation of the engine?
A. To slow down the engine
B. To allow unburnt fuel to leave the chamber safely
C. To prevent unburnt fuel from leaving the combustion chamber

Answer 4

C. To prevent unburnt fuel from leaving the combustion chamber

Question 5

Why must the combustion chamber minimize pressure loss during combustion?
A. To decrease the engine’s power output
B. To increase engine efficiency
C. To allow higher fuel consumption

Answer 5

B. To increase engine efficiency

Question 6

What is critical at the combustion chamber outlet for the first turbine stage?
A. Minimum fuel use
B. Uneven airflow distribution
C. Equal temperature distribution

Answer 6

C. Equal temperature distribution

Question 7

Why must the combustion chamber be small and light?
A. To enhance the cooling system
B. To save weight
C. To improve temperature distribution

Answer 7

B. To save weight

Question 8

What is necessary for materials in contact with the hot gas flow?
A. A dependable cooling system
B. Uneven pressure distribution
C. Lightweight construction

Answer 8

A. A dependable cooling system

Question 9

Why is a high operating lifetime for the combustion chamber important?
A. To minimize pressure loss
B. To reduce the time needed for replacement
C. To enhance cooling system efficiency

Answer 9

B. To reduce the time needed for replacement

Question 10

What are the two main components of a combustion chamber?
A. The combustion chamber casing and the flame tube (inside casing)
B. The inner casing and the outer casing
C. The flame tube and the cooling system

Answer 10

A. The combustion chamber casing and the flame tube (inside casing)

Question 11

What is a feature of the combustion chamber casing?
A. It is found inside the flame tube
B. It can be split into an inner and outer casing
C. It is the primary location for ignition

Answer 11

B. It can be split into an inner and outer casing

Question 12

What is the role of the combustion chamber casing in the engine?
A. It houses the flame tube and igniters
B. It takes air pressure loads and protects engine parts from hot combustion gases
C. It controls the air/fuel mixture

Answer 12

B. It takes air pressure loads and protects engine parts from hot combustion gases

Question 13

What does the combustion chamber casing shield?
A. The turbine blades
B. The internal and external engine parts from combustion gases
C. The air intake

Answer 13

B. The internal and external engine parts from combustion gases

Question 14

What does the combustion chamber housing support?
A. Only the fuel nozzles
B. The flame tube and components like fuel nozzles and igniter plugs
C. The turbine blades

Answer 14

B. The flame tube and components like fuel nozzles and igniter plugs

Question 15

What is the function of the flame tube?
A. To mix fuel and air
B. To control and guide the flame
C. To protect the combustion chamber casing

Answer 15

B. To control and guide the flame

Question 16

What is a characteristic of the flame tube’s construction?
A. It is a solid piece with no openings
B. It is made up of many segments with holes and slots
C. It is made of a single metal sheet

Answer 16

B. It is made up of many segments with holes and slots

Question 17

What happens to the fuel when sprayed into the compressed air in the combustion chamber?
A. It cools down
B. It vaporises and mixes with the airflow
C. It immediately ignites without mixing

Answer 17

B. It vaporises and mixes with the airflow

Question 18

How is the fuel-air mixture initially ignited in the combustion chamber?
A. By a spark from the turbine
B. By an igniter plug
C. By compression alone

Answer 18

B. By an igniter plug

Question 19

What happens to the ignition after combustion starts?
A. It stays on throughout flight
B. It switches off, but combustion continues as fuel and air are supplied
C. It switches off and combustion stops

Answer 19

B. It switches off, but combustion continues as fuel and air are supplied

Question 20

What is one primary condition necessary for correct and safe combustion?

A. The fuel must be sprayed cold
B. The ratio of air and fuel must be correct
C. The air velocity must be very high

Answer 20

B. The ratio of air and fuel must be correct

Question 21

Why must the air velocity be slow inside the combustion chamber?

A. To cool the combustion chamber
B. To ensure combustion is completed inside the combustion chamber
C. To increase engine speed

Answer 21

B. To ensure combustion is completed inside the combustion chamber

Question 22

What is the correct air-to-fuel ratio for complete combustion of a kerosene-air mixture?

A. 1 part air to 15 parts fuel
B. 15 parts air to 1 part fuel
C. 20 parts air to 1 part fuel

Answer 22

B. 15 parts air to 1 part fuel

Question 23

What are the two parts into which airflow from the compressor is split?

A. Primary airflow and secondary airflow
B. Hot airflow and cold airflow
C. Fast airflow and slow airflow

Answer 23

A. Primary airflow and secondary airflow

Question 24

How is the primary airflow from the compressor used in the combustion chamber?

A. It is used for the combustion process and makes up about 20% to 30% of the compressor airflow
B. It cools the engine parts and makes up about 50% of the airflow
C. It is exhausted directly without mixing and makes up about 70% of the airflow

Answer 24

A. It is used for the combustion process and makes up about 20% to 30% of the compressor airflow

Question 25

What happens to the airflow that does not enter the primary combustion zone? A. It bypasses the primary combustion zone and mixes with the hot gas in the dilution zone B. It is used only for cooling the turbine blades C. It is fully combusted in the primary zone

Answer 25

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

Question 26

What are the three different types of combustion chambers used on gas turbine engines? A. Can-type, can-annular, and annular combustion chambers B. Single-stage, multi-stage, and hybrid combustion chambers C. Radial, axial, and mixed-flow combustion chambers

Answer 26

A. Can-type, can-annular, and annular combustion chambers

Question 27

On what type of gas turbine engines are can-type (individual) combustion chambers commonly found? A. Old engines with centrifugal compressors B. Modern high-bypass turbofan engines C. Supersonic jet engines

Answer 27

A. Old engines with centrifugal compressors

Question 28

What does each can-type combustion chamber have its own of? A. Air supply duct, fuel nozzle, flame tube, and casing B. Shared air supply duct and fuel nozzle but individual flame tubes C. Only a shared casing and fuel nozzle

Answer 28

A. Air supply duct, fuel nozzle, flame tube, and casing

Question 29

What is an advantage of can-type combustion chambers? A. They are simple in design and can be individually removed B. They require complicated air supply ducts C. They are heavy and take up a lot of space

Answer 29

A. They are simple in design and can be individually removed

Question 30

What is one disadvantage of can-type combustion chambers? A. They are lightweight B. They require complicated air supply ducts from the compressor C. They have easy ignition between chambers

Answer 30

B. They require complicated air supply ducts from the compressor

Question 31

What is another disadvantage of multiple can-type combustion chambers? A. They are easy to ignite from one chamber to another B. They are heavy and need a lot of space C. They have very good structural strength

Answer 31

B. They are heavy and need a lot of space

Question 32

What is a key design feature of can-annular combustion chambers? A. Each flame tube has its own separate casing B. All flame tubes share a common outer and inner casing C. Flame tubes are installed in a single large chamber

Answer 32

B. All flame tubes share a common outer and inner casing

Question 33

What is an advantage of the can-annular combustion chamber compared to multiple-can chambers? A. It is smaller and lighter B. It is heavier and larger C. It has no aerodynamic losses

Answer 33

A. It is smaller and lighter

Question 34

What is a disadvantage of the can-annular combustion chamber? A. Ignition from one flame tube to another is difficult B. It has very low aerodynamic losses C. It is very simple in design

Answer 34

A. Ignition from one flame tube to another is difficult

Question 35

Which of the following is true about aerodynamic losses in a can-annular combustion chamber? A. They are quite high B. They are negligible C. They do not affect performance

Answer 35

A. They are quite high

Question 36

Which type of combustion chamber is most commonly used on modern gas turbine engines? A. Annular combustion chamber B. Can-type combustion chamber C. Can-annular combustion chamber

Answer 36

A. Annular combustion chamber

Question 37

How many annular flame tubes does the annular combustion chamber have? A. One B. Two C. Multiple

Answer 37

A. One

Question 38

What supports the annular flame tube in the combustion chamber? A. Inner and outer combustion chamber casing B. Only the outer casing C. Fuel nozzles

Answer 38

A. Inner and outer combustion chamber casing

Question 39

The combustion chamber casings in an annular combustion chamber are part of: A. The load-carrying engine structure B. The fuel system C. The ignition system

Answer 39

A. The load-carrying engine structure

Question 40

What are the three major parts of an annular combustion chamber? A. Dome, inner liner, outer liner B. Compressor, turbine, combustor C. Flame tube, fuel nozzle, casing

Answer 40

A. Dome, inner liner, outer liner

Question 41

What is the function of the dome in an annular combustion chamber? A. To hold the turbine assembly B. To contain openings for fuel nozzles surrounded by swirl vanes C. To reverse the airflow direction

Answer 41

B. To contain openings for fuel nozzles surrounded by swirl vanes

Question 42

What is a unique feature of a reverse flow annular combustion chamber? A. It has multiple flame tubes B. Airflow direction in the flame tube is opposite to the overall airflow direction C. It does not use swirl vanes

Answer 42

B. Airflow direction in the flame tube is opposite to the overall airflow direction

Question 43

Why is the reverse flow annular combustion chamber often used in small gas turbine engines and APUs? A. It reduces the engine's overall size B. It increases the fuel-air mixture ratio C. It eliminates the need for a dome

Answer 43

A. It reduces the engine's overall size

Question 44

What is one advantage of annular combustion chambers compared to other types? A. They are larger and heavier B. They have a smaller combustion area C. They are smaller and lighter for the same airflow

Answer 44

C. They are smaller and lighter for the same airflow

Question 45

What are the advantages of the large combustion area in an annular combustion chamber? A. It improves efficiency, ensures complete and smokeless combustion, and allows the flame to spread easily over the flame tube circumference. B. It requires less airflow and reduces overall efficiency. C. It complicates combustion, leading to incomplete burning of fuel.

Answer 45

A. It improves efficiency, ensures complete and smokeless combustion, and allows the flame to spread easily over the flame tube circumference.

Question 46

What is a disadvantage of annular combustion chambers? A. They have poor combustion efficiency B. They are difficult and time-consuming to remove C. They cannot handle large airflow

Answer 46

B. They are difficult and time-consuming to remove

Question 47

What are the typical sections of an annular combustion chamber? A. A combustion case, a flame tube, and external components fitted to the outer wall. B. A compressor case, a turbine blade, and an exhaust nozzle. C. A combustion liner, a spark plug, and an intake duct.

Answer 47

A. A combustion case, a flame tube, and external components fitted to the outer wall.

Question 48

What components are part of the combustion case assembly? A. An outer wall, an inner wall, and a diffuser. B. A flame tube, a spark plug, and a fuel injector. C. A turbine blade, an exhaust nozzle, and a pressure valve.

Answer 48

A. An outer wall, an inner wall, and a diffuser.

Question 49

What part of the combustion case is usually removable to allow installation of the flame tube? A. Rear portion of the inner wall B. Outer wall C. Diffuser

Answer 49

A. Rear portion of the inner wall

Question 50

Which integral parts are included in the combustion case assembly? A. Stator vanes of the last stage of the high-pressure compressor and the diffuser B. Igniter plugs and fuel pumps C. Turbine blades and exhaust cones

Answer 50

A. Stator vanes of the last stage of the high-pressure compressor and the diffuser

Question 51

What is the position of the igniter bosses relative to the fuel nozzles? A. Slightly behind the fuel nozzles B. In front of the fuel nozzles C. Above the fuel nozzles

Answer 51

A. Slightly behind the fuel nozzles

Question 52

How many igniter plugs are normally installed in the combustor case, and where are they usually located? A. Two igniter plugs, usually on the lower half of the combustor case B. One igniter plug, usually on the upper half of the combustor case C. Three igniter plugs, evenly spaced around the combustor case

Answer 52

A. Two igniter plugs, usually on the lower half of the combustor case

Question 53

What is the combustion case often known as on many engines, and what does it house? A. Compressor rear frame; it houses the bearings for the high-pressure rotor B. Turbine front frame; it houses the fuel nozzles C. Compressor front frame; it houses the igniter plugs

Answer 53

A. Compressor rear frame; it houses the bearings for the high-pressure rotor

Question 54

Which of the following are the main components of the flame tube assembly? A. Outer and inner liner, outer and inner cowl, dome B. Combustion case, diffuser, stator vanes C. Fuel nozzles, igniter plugs, bleed air ports

Answer 54

A. Outer and inner liner, outer and inner cowl, dome

Question 55

What does the dome section of the flame tube connect? A. The combustion case to the diffuser B. The inner liner with the outer liner C. The fuel nozzles to the igniter plugs

Answer 55

B. The inner liner with the outer liner

Question 56

What does each swirler usually have to hold in its centre? A. A bearing B. A nozzle tip C. A fuel injector

Answer 56

B. A nozzle tip

Question 57

How is the flame tube attached to the combustion case structure? A. It is bolted and fixed at both ends B. It is bolted and fixed at one end and moveable at the opposite end C. It is welded permanently in place

Answer 57

B. It is bolted and fixed at one end and moveable at the opposite end

Question 58

Where is the flame tube fixed in all three dimensions? A. At the front end B. At the aft end C. In the middle

Answer 58

B. At the aft end

Question 59

Where is the flame tube sometimes fixed to allow expansion at the rear? A. Front end of the combustion case B. Middle of the combustion case C. Rear end of the combustion case

Answer 59

A. Front end of the combustion case

Question 60

Which parts make up the two-piece flame tube? A. Outer liner and inner liner B. Dome and outer liner (one piece), and inner liner (separate part) C. Dome and inner liner (one piece), and outer liner (separate part)

Answer 60

B. Dome and outer liner (one piece), and inner liner (separate part)

Question 61

How is the dome centered in the combustion case? A. Using mounting pins B. Welded to the casing C. Bolted directly to the turbine

Answer 61

A. Using mounting pins

Question 62

Where does the primary airflow enter the flame tube? A. Through the swirl vanes B. Through the outer cowl C. Through the inner liner

Answer 62

A. Through the swirl vanes

Question 63

How does the secondary airflow enter the flame tube? A. Through the liners after passing the cowl B. Directly through the fuel nozzles C. Through the turbine blades

Answer 63

A. Through the liners after passing the cowl

Question 64

What does the secondary airflow form on the inner surface of the liners? A. A cooling film B. A fuel layer C. A combustion flame

Answer 64

A. A cooling film

Question 65

What is the purpose of the cooling film formed by the secondary airflow? A. To protect the liner from intense heat B. To increase combustion temperature C. To reduce airflow velocity

Answer 65

A. To protect the liner from intense heat

Question 66

What is the name of the cooling method where a film of air protects the liner? A. Film cooling B. Spray cooling C. Convection cooling

Answer 66

A. Film cooling

Question 67

What is the more sophisticated method of film cooling called? A. Transpiration cooling B. Spray cooling C. Convection cooling

Answer 67

A. Transpiration cooling

Question 68

What covers the inner surfaces of the flame tube liners in transpiration cooling? A. Detachable tiles B. Fixed plates C. Insulating foam

Answer 68

A. Detachable tiles

Question 69

How does the secondary airflow enter the flame tube in the transpiration cooling method? A. Through radial holes in the liner B. Through slots in the dome C. Through the outer casing

Answer 69

A. Through radial holes in the liner

Question 70

What is one of the most important requirements of modern gas turbine engines regarding exhaust gases? A. Increase noise levels B. Decrease pollution C. Increase fuel consumption

Answer 70

B. Decrease pollution

Question 71

Which pollutants are mainly found in the exhaust gas of gas turbine engines? A. Water vapor and oxygen B. Unburned fuel, hydrocarbons, carbon monoxide, and nitrogen oxides C. Carbon dioxide and nitrogen only

Answer 71

B. Unburned fuel, hydrocarbons, carbon monoxide, and nitrogen oxides

Question 72

What is a mixture called when there is too much fuel for the primary air in the combustion chamber? A. Lean mixture B. Rich mixture C. Perfect mixture

Answer 72

B. Rich mixture

Question 73

What happens if there is excessive fuel in the combustion chamber? A. Carbon monoxide build-up occurs B. Flame goes out C. Less pollution is produced

Answer 73

A. Carbon monoxide build-up occurs

Question 74

What is a lean mixture in the combustion chamber? A. Too much fuel for the air B. Insufficient fuel available C. Perfect fuel-to-air ratio

Answer 74

B. Insufficient fuel available

Question 75

What is a possible consequence of a lean mixture? A. More pollution B. The flame can go out C. Excess carbon monoxide is produced

Answer 75

B. The flame can go out

Question 76

What happens to carbon monoxide emissions at low combustion temperatures? A. They increase B. They decrease C. They stay the same

Answer 76

A. They increase

Question 77

What is the effect of increasing combustion temperature on nitrogen oxide emissions? A. Nitrogen oxide emissions increase B. Nitrogen oxide emissions decrease C. Nitrogen oxide emissions stay the same

Answer 77

A. Nitrogen oxide emissions increase

Question 78

How does the length of a dual dome combustion chamber compare to a standard combustion chamber? A. It is much shorter B. It is much longer C. It is the same length

Answer 78

A. It is much shorter

Question 79

What is the benefit of reducing the time exhaust gas spends in the hot area in a dual dome combustion chamber? A. Decreases build-up of nitrogen oxides B. Increases build-up of nitrogen oxides C. Has no effect on nitrogen oxides

Answer 79

A. Decreases build-up of nitrogen oxides

Question 80

What is the effect of the shorter length of the dual dome combustion chamber on exhaust gas? A. Reduces time the exhaust gas is in the hot area B. Increases time the exhaust gas is in the hot area C. Has no effect on the exhaust gas

Answer 80

A. Reduces time the exhaust gas is in the hot area