1000+ Compressors, Gas Turbines & Jet Engines MCQ for IBPS RRB [Solved]

1. Ratio of indicated H.P. and brake H.P. is known as
A. Mechanical efficiency
B. Volumetric efficiency
C. Isothermal efficiency
D. Adiabatic efficiency
Answer : A

2. Maximum temperature in a gas turbine is of the order of
A. 700°C
B. 2000°C
C. 1500°C
D. 1000°C
Answer : A

3. Isothermal compression efficiency, even when running at high speed, can be approached by using
A. Multistage compression
B. Cold water spray
C. Both (A) and (B) above
D. Fully insulating the cylinder
Answer : C

4. The combustion efficiency of a gas turbine using perfect combustion chamber is of the order of
A. 75 %
B. 85 %
C. 90 %
D. 99 %
Answer : D

5. The work done per unit mass of air in compression will be least when n is equal to
A. 1
B. 1.2
C. 1.3
D. 1.4
Answer : A

6. The intercooler pressure, for minimum work required, for a two stage reciprocating air compressor, is given by (where p? = Intake pressure of air, p? = Intercooler pressure, and p? = Delivery pressure of air)
A. p? = p? × p?
B. p? = p?/p?
C. p? = p? × p?
D. p? = p?/p?
Answer : C

7. The ratio of work done per cycle to the swept volume in case of compressor is called
A. Compression index
B. Compression ratio
C. Compressor efficiency
D. Mean effective pressure
Answer : D

8. What will be the volume of air at 327°C if its volume at 27°C is 1.5 m³/ mt?
A. 3 m³/ mt.
B. 1.5 m³/ mt.
C. 18 m³/ mt.
D. 6 m³/ mt.
Answer : A

9. The ideal efficiency of simple gas turbine cycle depends on
A. Pressure ratio
B. Maximum cycle temperature
C. Minimum cycle temperature
D. All of the above
Answer : A

10. 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

11. Pick up the correct statement
A. Large gas turbines use radial inflow turbines
B. Gas turbines have their blades similar to steam turbine
C. Gas turbine's blade will appear as impulse section at the hub and as a reaction section at tip
D. Gas turbines use both air and liquid cooling
Answer : C

12. The ratio of the discharge pressure to the inlet pressure of air is called
A. Compression ratio
B. Expansion ratio
C. Compressor efficiency
D. Volumetric efficiency
Answer : A

13. The stagnation pressure rise in a centrifugal compressor takes place
A. In the diffuser only
B. In the impeller only
C. In the diffuser and impeller
D. In the inlet guide vanes only
Answer : C

14. Isothermal compression though most efficient, but is not practicable because
A. It requires very big cylinder
B. It does not increase pressure much
C. It is impossible in practice
D. Compressor has to run at very slow speed to achieve it
Answer : D

15. 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

16. The compressor performance at higher altitude compared to sea level will be
A. Same
B. Higher
C. Lower
D. Dependent on other factors
Answer : C

17. The volume of air sucked by the compressor during its suction stroke is called
A. Free air delivery
B. Compressor capacity
C. Swept volume
D. None of these
Answer : C

18. Which of the following statement is correct relating to rocket engines?
A. The combustion chamber in a rocket engine is directly analogous to the reservoir of a supersonic wind tunnel
B. The stagnation conditions exist at the combustion chamber
C. The exit velocities of exhaust gases are much higher than those in jet engine
D. All of the above
Answer : D

19. An air compressor may be controlled by
A. Throttle control
B. Clearance control
C. Blow off control
D. Any one of the above
Answer : D

20. 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

21. Which one of the following is the effect of blade shape on performance of a centrifugal compressor?
A. Backward curved blades has poor efficiency
B. Backward curved blades lead to stable performance
C. Forward curved blades has higher efficiency
D. Forward curved blades produce lower pressure ratio
Answer : D

22. To avoid moisture troubles, the branch connections from compressed air lines should be taken from
A. Top side of main
B. Bottom side of main
C. Left side of main
D. Right side of main
Answer : A

23. Compression efficiency is compared against
A. Ideal compression
B. Adiabatic compression
C. Isentropic compression
D. Isothermal compression
Answer : D

24. Reheating in gas turbine results in
A. Increase of work ratio
B. Decrease of thermal efficiency
C. Decrease of work ratio
D. Both (A) and (B) above
Answer : D

25. Euler's equation is applicable for
A. Centrifugal compressor
B. Axial compressor
C. Pumps
D. All of the above
Answer : D

26. During peak load periods, the best method of controlling compressors is
A. Start-stop motor
B. Constant speed unloader
C. Relief valve
D. Variable speed
Answer : B

27. The mass of gas turbine per kW developed is about ________ as that of an I.C. engine.
A. Same
B. One-half
C. One fourth
D. One sixth
Answer : D

28. Inter-cooling in multistage compressors is done
A. To cool the air during compression
B. To cool the air at delivery
C. To enable compression in two stages
D. To minimise the work of compression
Answer : D

29. The following is true for an open cycle gas turbine having exhaust heat exchanger. Atmospheric air before entering the compressor is
A. Heated
B. Compressed air before entering the combustion chamber is heated
C. Bled gas from turbine is heated and readmitted for complete expansion
D. Exhaust gases drive the compressor
Answer : B

30. Only rocket engines can be propelled to space because
A. They can generate very high thrust
B. They have high propulsion efficiency
C. These engines can work on several fuels
D. They are not air breathing engines
Answer : D

31. 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

32. Pick up the wrong statement
A. Large gas turbines employ axial flow compressors
B. Axial flow compressors are more stable than centrifugal type compressors but not as efficient
C. Axial flow compressors have high capacity and efficiency
D. Axial flow compressors have instability region of operation
Answer : B

33. The compression ratio for the compressor is always __________ unity.
A. Equal to
B. Less than
C. More than
D. None of these
Answer : C

34. Standard air is the air at
A. Atmospheric conditions at any specific location
B. 20°C and 1 kg/cm² and relative humidity 36%
C. 0°C and standard atmospheric conditions
D. 15°C and 1 kg/cm²
Answer : B

35. 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

36. The axial flow compressor is preferred in aircraft gas turbines because of
A. Low frontal area
B. Higher thrust
C. High pressure rise
D. None of these
Answer : A

37. 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

38. The capacity of compressor will be highest when its intake temperature is
A. Lowest
B. Highest
C. Anything
D. Atmospheric
Answer : D

39. 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

40. Volumetric efficiency of a compressor decreases with ________ in compression ratio.
A. Decrease
B. Increase
C. Remain same
D. Does not change
Answer : B

41. The advantage of multistage compression over single stage compression is
A. Lower power consumption per unit of air delivered
B. Higher volumetric efficiency
C. Decreased discharge temperature
D. All of the above
Answer : D

42. The overall efficiency of the compressed air system is the
A. Ratio of shaft output of the air motor to the shaft input to the compressor
B. Ratio of shaft input to the compressor to the shaft output of air motor
C. Product of shaft output of air motor and shaft input to the compressor
D. None of the above
Answer : A

43. Pick up the correct statement
A. Gas turbine uses low air-fuel ratio to economise on fuel
B. Gas turbine uses high air-fuel ratio to reduce outgoing temperature
C. Gas turbine uses low air-fuel ratio to develop the high thrust required
D. All of the above
Answer : B

44. In a four stage compressor, if the pressure at the first and third stage is 1 bar and 16 bar, then the delivery pressure at the fourth stage will be
A. 1 bar
B. 16 bar
C. 64 bar
D. 256 bar
Answer : C

45. Out of the following, from where you will prefer to take intake for air compressor
A. From an air conditioned room maintained at 20°C
B. From outside atmosphere at 1°C
C. From coal yard side
D. From a side where cooling tower is located nearby
Answer : D

46. 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

47. Axial flow compressor resembles
A. Centrifugal pump
B. Reciprocating pump
C. Turbine
D. Sliding vane compressor
Answer : C

48. Which of the following statement is correct as regard to centrifugal compressors?
A. The flow of air is parallel to the axis of the compressor
B. The static pressure of air in the impeller increases in order to provide centripetal force on the air
C. The impeller rotates at high speeds
D. The maximum efficiency is higher than multistage axial flow compressors
Answer : B

49. Rotary compressors are used for delivering
A. Small quantities of air at high pressures
B. Large quantities of air at high pressures
C. Small quantities of air at low pressures
D. Large quantities of air at low pressures
Answer : D

50. Losses in a centrifugal compressor are due to
A. Inlet losses
B. Impeller channel losses
C. Diffuser losses
D. All of the above
Answer : D