Compressors, Gas Turbines & Jet Engines MCQ Solved Paper for IBPS PO

1. It is not possible to use closed gas turbine cycle in aeronautical engines because
A. It is inefficient
B. It is bulky
C. It requires cooling water for its operation
D. None of the above
Answer : C

2. The compressor capacity with decrease in suction temperature
A. Increases
B. Decreases
C. Remain unaffected
D. May increase or decrease depending on compressor capacity
Answer : A

3. A rocket engine uses ________ for the combustion of its fuel.
A. Surrounding air
B. Compressed atmospheric air
C. Its own oxygen
D. None of these
Answer : C

4. Pressure ratio in gas turbines is the ratio of
A. Compressor pressure ratio
B. Highest pressure to exhaust pressure
C. Inlet pressure to exhaust pressure
D. Pressures across the turbine
Answer : B

5. The performance of air compressor at high altitudes will be ________ as compared to that at sea level.
A. Same
B. Lower
C. Higher
D. None of these
Answer : B

6. The efficiency and work ratio of a gas turbine plant can be increased by
A. Adding heat exchanger
B. Injecting water in/around combustion chamber
C. Reheating the air after partial expansion in the turbine
D. All of the above
Answer : D

7. Volumetric efficiency of a compressor with clearance volume
A. Increases with increase in compression ratio
B. Decreases with increase in compression ratio
C. In not dependent upon compression ratio
D. May increase/decrease depending on compressor capacity
Answer : B

8. In a single stage, single acting reciprocating air compressor, without clearance volume, the workdone is minimum during
A. Isothermal compression
B. Isentropic compression
C. Polytropic compression
D. None of these
Answer : A

9. In a high pressure compressor, the delivery pressure is
A. 1 to 5 bar
B. 5 to 8 bar
C. 8 to 10 bar
D. 10 to 15 bar
Answer : C

10. In a jet propulsion
A. The propulsive matter is ejected from within the propelled body
B. The propulsive matter is caused to flow around the propelled body
C. Its functioning does not depend upon presence of air
D. None of the above
Answer : B

11. The ratio of specific weight/h.p. of gas turbine and I.C engines may be typically of the order of
A. 1 : 1
B. 2 : 1
C. 4 : 1
D. 1 : 6
Answer : D

12. Volumetric efficiency is
A. The ratio of stroke volume to clearance volume
B. The ratio of the air actually delivered to the amount of piston displacement
C. Reciprocal of compression ratio
D. Index of compressor performance
Answer : B

13. Reciprocating air compressor is best suited for
A. Large quantity of air at high pressure
B. Small quantity of air at high pressure
C. Small quantity of air at low pressure
D. Large quantity of air at low pressure
Answer : A

14. Reheating in a multistage expansion gas turbine __________ compressor work.
A. Has no effect on
B. Decreases
C. Increases
D. None of these
Answer : B

15. Which is false statement about advantages of multistage compressor in comparison to single stage compressor?
A. Less power requirement
B. Better mechanical balance
C. Less loss of air due to leakage past the cylinder
D. Lower volumetric efficiency
Answer : D

16. The overall isothermal efficiency of compressor is defined as the ratio of
A. Isothermal h.p. to the BHP of motor
B. Isothermal h.p. to adiabatic h.p.
C. Power to drive compressor to isothermal h.p.
D. Work to compress air isothermally to work for actual compression
Answer : A

17. Ramjet engine
A. Is self operating at zero flight speed
B. Is not self operating at zero flight speed
C. Requires no air for its operation
D. Produces a jet consisting of plasma
Answer : B

18. Phenomenon of choking in compressor means
A. No flow of air
B. Fixed mass flow rate regardless of pressure ratio
C. Reducing mass flow rate with increase in pressure ratio
D. Increased inclination of chord with air steam
Answer : B

19. In a compressor, free air delivered is the actual volume delivered at the stated pressure reduced to
A. N.T.P. conditions
B. Intake temperature and pressure conditions
C. 0°C and 1 kg/cm²
D. 20°C and 1 kg/cm²
Answer : B

20. The ratio of isentropic work to Euler work is known as
A. Pressure coefficient
B. Work coefficient
C. Polytropic reaction
D. Slip factor
Answer : A

21. The air is delivered ________ in one revolution in case of a three lobbed rotor.
A. Two times
B. Three times
C. Four times
D. Six times
Answer : D

22. A closed cycle gas turbine gives ________ efficiency as compared to an open cycle gas turbine.
A. Same
B. Lower
C. Higher
D. None of these
Answer : C

23. Stalling of blades in axial flow compressor is the phenomenon of
A. Air stream blocking the passage
B. Motion of air at sonic velocity
C. Unsteady periodic and reversed flow
D. Air stream not able to follow the blade contour
Answer : D

24. A closed cycle gas turbine works on
A. Carnot cycle
B. Rankine cycle
C. Ericsson cycle
D. Joule cycle
Answer : D

25. In the cross compounding of the gas turbine plant
A. H.P. compressor is connected to H.P. turbine and L.P. compressor to L.P. turbine
B. H.P. compressor is connected to L.P. turbine and L.P. compressor is connected to H.P. turbine
C. Both the arrangements can be employed
D. All are connected in series
Answer : B

26. The compressor capacity is defined as the
A. Actual volume of the air delivered by the compressor when reduced to normal temperature and pressure conditions
B. Volume of air delivered by the compressor
C. Volume of air sucked by the compressor during its suction stroke
D. None of the above
Answer : B

27. Producer gas is produced by
A. Carbonisation of coal
B. Passing steam over incandescent coke
C. Passing air and a large amount of steam over waste coal at about 65°C
D. Partial combustion of coal, coke, anthracite coal or charcoal in a mixed air steam blast
Answer : D

28. The ratio of the increase in pressure in rotor blades to total increase in pressure in the stage is called
A. Pressure ratio
B. Pressure coefficient
C. Degree of reaction
D. Slip factor
Answer : C

29. Which of the following plants is smallest and lightest for generating a given amount of power?
A. Gas turbine plant
B. Petrol engine
C. Diesel engine
D. Solar plant
Answer : A

30. Temperature of gases at end of compression as compared to exhaust gases in a gas turbine is
A. Higher
B. Lower
C. Equal
D. Cant be compared
Answer : B

31. Inter cooling in compressors
A. Cools the delivered air
B. Results in saving of power in compressing a given volume to given pressure
C. Is the standard practice for big compressors
D. Enables compression in two stages
Answer : B

32. Gas turbines for power generation are normally used
A. To supply base load requirements
B. To supply peak load requirements
C. To enable start thermal power plant
D. In emergency
Answer : B

33. If the clearance ratio for a reciprocating air compressor is 'K', then its volumetric efficiency is given by
A. 1 - k + k (p?/p?)^1/n
B. 1 + k - k (p?/p?)^1/n
C. 1 - k + k (p?/p?) ^{n- 1/n}
D. 1 + k - k (p?/p?) ^n-1/n
Answer : B

34. A simple turbojet engine is basically
A. A propeller system
B. Gas turbine engine equipped with a propulsive nozzle and diffuse
C. Chemical rocket engine
D. Ramjet engine
Answer : B

35. The pressure and temperature conditions of air at the suction of compressor are
A. Atmospheric
B. Slightly more than atmospheric
C. Slightly less than atmospheric
D. Pressure slightly less than atmospheric and temperature slightly more than atmospheric
Answer : D

36. Which is false statement about multistage compression?
A. Power consumption per unit of air delivered is low
B. Volumetric efficiency is high
C. It is best suited for compression ratios around 7:1
D. The moisture in air is condensed in the intercooler
Answer : B

37. Mining industry usually employs following motive power
A. A.C. electric motor
B. Compressed air
C. Petrol engine
D. Diesel engine
Answer : B

38. The closed cycle in gas turbines
A. Provides greater flexibility
B. Provides lesser flexibility
C. In never used
D. Is used when gas is to be burnt
Answer : A

39. Gas turbines use following type of air compressor
A. Centrifugal type
B. Reciprocating type
C. Lobe type
D. Axial flow type
Answer : D

40. Turbofan engine employs
A. One air stream
B. Two or more air streams
C. No air stream
D. Solid fuel firing
Answer : B

41. Actual compression curve is
A. Same as isothermal
B. Same as adiabatic
C. Better than isothermal and adiabatic
D. In between isothermal and adiabatic
Answer : D

42. The maximum compression ratio in an actual single stage axial flow compressor is of the order of
A. 1 : 1.2
B. 1 : 2
C. 1 : 5
D. 1 : 10
Answer : A

44. In jet engines, for the efficient production of large power, fuel is burnt in an atmosphere of
A. Vacuum
B. Atmospheric air
C. Compressed air
D. Oxygen alone
Answer : C

45. Pick up the wrong statement
A. Pulsejet requires no ambient air for propulsion
B. Ramjet engine has no turbine
C. Turbine drives compressor in a Turbojet
D. Bypass turbojet engine increases the thrust without adversely affecting, the propulsive efficiency and fuel economy
Answer : A

46. A gas turbine used in air craft should have
A. High h.p. and low weight
B. Low weight and small frontal area
C. Small frontal area and high h.p.
D. High speed and high h.p
Answer : B

47. The type of rotary compressor used in gas turbines, is of
A. Centrifugal type
B. Axial flow type
C. Radial flow type
D. None of these
Answer : B

48. Clearance volume in actual reciprocating compressors is essential
A. To accommodate Valves in the cylinder head
B. To provide cushioning effect
C. To attain high volumetric efficiency
D. To provide cushioning effect and also to avoid mechanical bang of piston with cylinder head
Answer : D

49. The volumetric efficiency for reciprocating air compressors is about
A. 10 to 40 %
B. 40 to 60 %
C. 60 to 70 %
D. 70 to 90 %
Answer : D

50. Maximum work is done in compressing air when the compression is
A. Isothermal
B. Adiabatic
C. Polytropic
D. None of the above
Answer : B