DGCA & EASA Module 15 : Part-5 Engine Combustion Section Question
DGCA & EASA Module 15 : Part-5 Engine Combustion Section Question-Answer
1. In a turbojet engine, combustion occurs at.
A. constant velocity.
B. constant volume.
C. constant pressure.
Ans : constant pressure.
Explanation: Jepperson Gas Turbine Powerplants page 2-18 refers.
2. A tubo-annular gas turbine combustion systemconsists of.
A. a number of flame tubes in an annular air casing.
B. a number of flame tubes each with its own air casing.
C. an annular flame tube in an annular air casing.
Ans : a number of flame tubes in an annular air casing.
Explanation: Rolls Royce book page 40 para 18.
3. In which type of turbine engine combustion chamber is the case and liner removed and installed as one unit during routine maintenance?.
A. Cannular.
B. Annular.
C. Can.
Ans : Can.
Explanation: Jeppesen A&P Powerplant Textbook 3-23.
4. In a turboprop engine, combustion takes place at constant.
A. pressure.
B. density.
C. volume.
Ans : pressure.
Explanation: Jeppesen A&P Powerplant Textbook 3-29.
5. The air passing through the combustion chamber is.
A. entirely combined with fuel and burned.
B. used to support combustion and to cool the engine.
C. speeded up and heated by the action of the turbines.
Ans : used to support combustion and to cool the engine.
Explanation: NIL.
6. The air used for combustion is.
A. Primary and secondary.
B. Primary.
C. Secondary.
Ans : Primary.
Explanation: Air through the core engine is defined as primary air.
7. Combustion chamber flame temperature is in the order of.
A. 2000°Centigrade.
B. 2000°Fahrenheit.
C. 2000°K.
Ans : 2000°Centigrade.
Explanation: NIL.
8. Hot spots in the combustion section of a turbojet engine are possible.
A. dirty compressor blades.
B. malfunctioning fuel nozzles.
C. faulty igniter plugs.
Ans : malfunctioning fuel nozzles.
Explanation: NIL.
9. Another name for a cannular combustion chamber is.
A. turbo-annular.
B. multiple can.
C. can-annular.
Ans : can-annular.
Explanation: NIL.
10. Another name for a cannular combustion chamber is.
A. annular.
B. tubo-annular.
C. multiple can.
Ans : tubo-annular.
Explanation: NIL.
11. The approximate percentage of the mass airflow taken in by the flame tube snout is.
A. 82%.
B. 8%.
C. 18%.
Ans : 18%.
Explanation: Rolls Royce book page 36 para 6.
12. What component creates a vortex in a gas turbine flame tube?.
A. Tertiary hole.
B. Swirl vanes.
C. Cascade vanes.
Ans : Swirl vanes.
Explanation: NIL.
13. In the combustion chamber.
A. static pressure and volume remains constant.
B. static pressure decreases slightly and volume increases.
C. static pressure and volume decreases.
Ans : static pressure decreases slightly and volume increases.
Explanation: Jepperson Gas Turbine Powerplants Page 2-18 refers.
14. Which of the following types of combustion sections are used in aircraft turbine engines?.
A. Annular, variable, and cascade vane.
B. Multiple can, annular, and can-annular.
C. Can, multiple can, and variable.
Ans : Multiple can, annular, and can-annular.
Explanation: NIL.
15. Secondary air in the combustion chamber is used for.
A. increasing axial velocity of gases.
B. combustion.
C. cooling.
Ans : cooling.
Explanation: Jeppesen Gas Turbine Powerplants Page 3-31 Refers.
16. Duplex burners have.
A. two calibrated outlets.
B. variable orifices.
C. a spring.
Ans : two calibrated outlets.
Explanation: Rolls Royce The Jet Engine Page 116 Refers.
17. The overall air/fuel ratio of a combustion chamber can vary between.
A. 45:1 and 130:1.
B. 130:1 and 200:1.
C. 10:1 and 45:1.
Ans : 45:1 and 130:1.
Explanation: Rolls Royce The Jet Engine page 36 refers.
18. When light-up takes place.
A. the nozzle guide vanes spread the heat to adjacent flame tubes.
B. interconnectors spread the heat to adjacent flame tubes.
C. each flame tube is isolated from its neighbours.
Ans : interconnectors spread the heat to adjacent flame tubes.
Explanation: Rolls Royce The Jet Engine page 39 refers.
19. Why do the holes in the body of the duple burner provide air to the shroud around the burner head?.
A. To assist atomisation of the fuel at slow running.
B. To reduce burner temperature.
C. To minimise carbon formation on the burner face.
Ans : To minimise carbon formation on the burner face.
Explanation: Rolls Royce The Jet Engine figure 10.18 refers.
20. The air passing through the combustion chamber of a jet engine is.
A. entirely combined with fuel and burned.
B. used to support combustion and to cool the engine.
C. speeded up and heated by the action of the turbines.
Ans : used to support combustion and to cool the engine.
Explanation: Rolls Royce The Jet Engine page 37 refers.
21. A toroidal vortex is.
A. a vapour trail visible in moist air conditions.
B. a region in the combustion chamber of low velocity re-circulation.
C. a bull-nosed cowling for deflecting air from the static.
Ans : a region in the combustion chamber of low velocity re-circulation.
Explanation: Rolls Royce The Jet Engine page 36 refers.
22. Why is it necessary to have a combustion drain system?.
A. To prevent pressure build up in the combustion chamber.
B. To prevent initial over-fuelling on start up or hot start.
C. To allow water in the combustor to drain away.
Ans : To prevent initial over-fuelling on start up or hot start.
Explanation: Excess fuel is drained on shutdown to avoid a subsequent hot start.
23. What is a cannular combustion system?.
A. One common flame tube closed in a common air casing.
B. A set of flame tubes, each mounted in a separate air casing.
C. A set of flame tubes, enclosed in a common air casing.
Ans : A set of flame tubes, enclosed in a common air casing.
Explanation: Also known as tubo-annular see Rolls Royce The Jet Engine page 41.
24. The flame temperature is approximately.
A. 1400°Centigrade.
B. 2000°Centigrade.
C. 500°Centigrade.
Ans : 2000°Centigrade.
Explanation: Rolls Royce The Jet Engine page 37 refers.
25. Fuel entering the combustion chamber from an atomizer spray nozzle enters as.
A. fuel in air pulses.
B. a fuel/air mixture.
C. fuel continuously.
Ans : a fuel/air mixture.
Explanation: Rolls Royce The Jet Engine page 117 refers.
26. An advantage of an annular combustion system is.
A. unrestricted airflow at maximum RPM.
B. diameter of engine is reduced due to the cans being smaller.
C. decrease in combustor length compared to a tubo-annular combustor of the same output.
Ans : decrease in combustor length compared to a tubo-annular combustor of the same output.
Explanation: Rolls Royce The Jet Engine Page 40 refers.
27. How is the combustion chamber drain valve closed?.
A. By 12th stage compressor air pressure.
B. By a return spring.
C. By combustion chamber gas pressure.
Ans : By combustion chamber gas pressure.
Explanation: Jeppesen Aircraft Gas Turbine Powerplant Page 7-59 refers.
28. Which statement is true regarding the air passing through the combustion section of a jet engine?.
A. Most is used for engine cooling.
B. Most is used to support combustion.
C. A small percentage is frequently bled off at this point to be used for air-conditioning and/or other pneumatic powered systems.
Ans : Most is used for engine cooling.
Explanation: NIL.
29. How are combustion liner walls cooled in a gas turbine engine?.
A. By secondary air flowing through the combustion chamber.
B. By bleed air vented from the engine air inlet.
C. By the pattern of holes and louvers cut in the diffuser section.
Ans : By secondary air flowing through the combustion chamber.
Explanation: NIL.
30. Dilution air is placed.
A. in the dilution zone of the combustion chamber after the primary zone.
B. in the primary zone of the combustion chamber.
C. in the swirl vanes of the combustor.
Ans : in the dilution zone of the combustion chamber after the primary zone.
Explanation: The air cools and adds to the mass flow.
31. A Duplex burner uses.
A. small burner at low RPM and both burner at hi RPM.
B. small burner at low RPM and large burner at hi RPM.
C. both burners at low and hi RPM.
Ans : small burner at low RPM and both burner at hi RPM.
Explanation: Jeppesen A and P Technician Powerplant Textbook 7-66.
32. The approximate percentage of the mass airflow which bypasses the flame tube snout is.
A. 8%.
B. 82%.
C. 18%.
Ans : 82%.
Explanation: Rolls Royce The Jet Engine page 36 shows 20%.
33. Flame stabilization in a combustion chamber is achieved by.
A. the correct burner pressure.
B. the airflow pattern.
C. the correct air/fuel ratio.
Ans : the airflow pattern.
Explanation: Rolls Royce The Jet Engine page 36 refers.
34. Fuel nozzles are cleaned.
A. with a rag and solvent.
B. in-situ with carbon solution.
C. in-situ with detergent solution.
Ans : in-situ with detergent solution.
Explanation: Jeppesen Aircraft Gas Turbine Powerplants page 7-54 refers.
35. When heat is added to the combustion chamber.
A. pressure increases rapidly volume remains constant.
B. pressure changes slightly and volume increases.
C. pressure rises at chamber outlet.
Ans : pressure changes slightly and volume.
Explanation: Rolls Royce The Jet Engine page 12 figure 2-2 refers.
36. A shroud placed around fuel nozzles.
A. flakes the carbon to minimise accumulations.
B. prevents carbon build up.
C. builds up carbon deposits to assist atomisation.
Ans : prevents carbon build up.
Explanation: Jeppesen Aircraft Gas turbine Powerplants page 7-54 refers.
37. Carbon forming on fuel spray nozzles will have the effect of.
A. increasing the combustion chamber pressure ratio.
B. producing turbulent air flow.
C. changing the fuel spray angle.
Ans : changing the fuel spray angle.
Explanation: Carbon on the fuel nozzles will distort fuel spray flow and direction. This can cause hot spots within the combustion chamber.
38. Combustor air that is not used to support combustion.
A. will film cool the liner and dilute combustion chamber exit temperature.
B. is by-pass air.
C. is considered as the total air flow.
Ans : will film cool the liner and dilute combustion chamber exit temperature.
Explanation: This air is known as secondary or tertiary combustor air.
39. At high rotational speed at sea level, a duple burner would be passing fuel via the.
A. main nozzle.
B. primary nozzle.
C. primary and the main nozzle.
Ans : primary and the main nozzle.
Explanation: The duple nozzle is also called the duplex nozzle. RR the Jet Engine page 116 refers.
40. The fabricated liner of a flame tube is achieved mainly by.
A. argon arc process.
B. electric resistance welding.
C. oxyacetylene welding.
Ans : argon arc process.
Explanation: an argon arc (T.I.G) welding is used to repair combustion liners, it is assumed that this is also the manufacturing process. can anyone confirm this with a reference.
41. Why is it necessary to have a combustion chamber drain?.
A. To allow unburnt fuel to drain away.
B. To prevent pressure build-up in the combustion chamber.
C. To allow fuel to return to LP when H.P cock is closed.
Ans : To allow unburnt fuel to drain away.
Explanation: The residual fuel must be drained off to prevent subsequent wet starts.
42. The purpose of the swirl vanes in the combustion chamber is to produce.
A. flame re-circulation.
B. gas re-circulation.
C. adequate mixing of fuel and air.
Ans : gas re-circulation.
Explanation: Rolls Royce The Jet Engine page 36 paragraph 7 refers to recirculating gases.
43. A vaporising burner injects fuel vapour.
A. with the airflow.
B. across the airflow.
C. against the airflow.
Ans : against the airflow.
Explanation: Jeppesen Aircraft Gas Turbine Powerplants page 7-55 refers.
44. A duplex burner in a gas turbine engine has 2 orifices.
A. one for water injection and one for fuel flow.
B. one for low speed conditions the second used for high speed conditions.
C. one for normal flow conditions and the 2nd one to increase the normalmaximum flow.
Ans : one for low speed conditions the second used for high speed conditions.
Explanation: This is a most right answer. Primary flow only normally occurs only during start (low flow)
45. A combustion chamber has a.
A. convergent inlet, divergent outlet.
B. convergent inlet, convergent outlet.
C. divergent inlet, convergent outlet.
Ans : divergent inlet, convergent outlet.
Explanation: Rolls Royce - The Jet Engine (4th edition) figure 4-1, 4-3, 4-5, 4-9, pgs 36 - 42.
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