Compressors, Gas Turbines & Jet Engines 1000+ MCQ with answer for ESIC

1. Isothermal compression efficiency can be attained by running the compressor
A. At very high speed
B. At very slow speed
C. At average speed
D. At zero speed
Answer : B

2. To avoid moisture troubles, the compressed air main line should
A. Rise gradually towards the point of use
B. Drop gradually towards the point of use
C. Be laid vertically
D. Be laid exactly horizontally
Answer : B

3. Which of the following statement is correct?
A. The reciprocating compressors are best suited for high pressure and low volume capacity
B. The effect of clearance volume on power consumption is negligible for the same volume of discharge
C. Both (A) and (B)
D. None of these
Answer : C

4. The gas in cooling chamber of a closed cycle gas turbine is cooled at
A. Constant volume
B. Constant temperature
C. Constant pressure
D. None of these
Answer : C

5. 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

6. 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

7. 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

8. Axial flow compressor has the following advantage over centrifugal compressor
A. Larger air handling ability per unit frontal area
B. Higher pressure ratio per stage
C. Aerofoil blades are used
D. Higher average velocities
Answer : A

9. Diffuser in a compressor is used to
A. Increase velocity
B. Make the flow streamline
C. Convert pressure energy into kinetic energy
D. Convert kinetic energy into pressure energy
Answer : D

10. Pick up the wrong statement
A. Centrifugal compressors deliver practically constant pressure over a considerable range of capacities
B. Axial flow compressors have a substantially constant delivery at variable pressures
C. Centrifugal compressors have a wider stable operating range than axial flow compressors
D. Axial flow compressors are bigger in diameter compared to centrifugal type
Answer : D

11. If infinite number of heaters be used in a gas turbine, then expansion process in turbine approaches
A. Isothermal
B. Isentropic
C. Adiabatic
D. Isochoric
Answer : A

12. 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

13. 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

14. The air power of the compressor is also known as
A. Indicated power
B. Brake power
C. Frictional power
D. None of these
Answer : A

15. In an axial flow compressor, the ratio of pressure in the rotor blades to the pressure rise in the compressor in one stage is known as
A. Work factor
B. Slip factor
C. Degree of reaction
D. Pressure coefficient
Answer : C

16. The air entry velocity m a rocket as compared to aircraft is
A. Same
B. More
C. Less
D. Zero
Answer : D

17. The indicated work per unit mass of air delivered is
A. Directly proportional to clearance volume
B. Greatly affected by clearance volume
C. Not affected by clearance volume
D. Inversely proportional to clearance volume
Answer : C

18. 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

19. Open cycle gas turbine works on
A. Brayton or Atkinson cycle
B. Rankine cycle
C. Carnot cycle
D. Erricson cycle
Answer : A

20. Standard air is the air at ________ and relative humidity of 36 percent.
A. 0.1 bar and 20°C
B. 1 bar and 20°C
C. 0.1 bar and 40°C
D. 1 bar and 40°C
Answer : B

21. For a two stage compressor, if index of compression for higher stage is greater than index of compression for lower stage, then the optimum pressure as compared to ideal case will
A. Increase
B. Decrease
C. Remain unaffected
D. Other factors control it
Answer : A

22. Propulsion efficiency of the following order is obtained in practice
A. 34 %
B. 50 %
C. 60 %
D. 72 %
Answer : C

23. 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

24. Rotary 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 : B

25. 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

26. 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

27. Gas turbine cycle with regenerator
A. Increases thermal efficiency
B. Allows high compression ratio
C. Decreases heat loss is exhaust
D. Allows operation at very high altitudes
Answer : A

28. Efficiency of gas turbine is increased by
A. Reheating
B. Inter cooling
C. Adding a regenerator
D. All of the above
Answer : C

29. In turbo fan engine, the jet velocity as compared to turbojet engine is
A. Less
B. More
C. Same
D. May be less or more depending upon speed
Answer : A

30. The most efficient method of compressing air is to compress it
A. Isothermally
B. Adiabatically
C. Isentropically
D. Isochronically
Answer : A

31. Pick up the wrong statement about advantages of multistage compression
A. Better lubrication is possible advantages of multistage
B. More loss of air due to leakage past the cylinder
C. Mechanical balance is better
D. Air can be cooled perfectly in between
Answer : B

32. The area of actual indicator diagram on an air compressor as compared to area of ideal indicator diagram is
A. Less
B. More
C. Same
D. More/less depending on compressor capacity
Answer : B

33. 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

34. Reheating in multistage expansion gas turbine results in
A. High thermal efficiency
B. Reduction in compressor work
C. Decrease of heat loss in exhaust
D. Maximum work output
Answer : D

35. The volumetric efficiency of compressor with increase in compression ratio will
A. Increase
B. Decrease
C. Remain same
D. May increase or decrease depending on clearance volume
Answer : B

36. 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

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

38. 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

39. The capacity of a compressor is expressed in
A. kg/m²
B. kg/m³
C. m³/min
D. m³/kg
Answer : C

40. The fuel consumption in gas turbines is accounted for by
A. Lower heating value
B. Higher heating value
C. Heating value
D. Higher calorific value
Answer : A

41. 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

42. The thermal efficiency of a gas turbine as compared to a diesel plant is
A. Same
B. More
C. Less
D. Depends on other factors
Answer : C

43. Gas turbine as compared to steam turbine
A. Requires less space for installation
B. Has compressor and combustion chamber
C. Has less efficiency
D. All of these
Answer : D

44. 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

45. Which is false statement about air receivers?
A. These are used to dampen pulsations
B. These act as reservoir to take care of sudden demands
C. These increase compressor efficiency
D. These knock out some oil and moisture
Answer : C

46. 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

47. A 3 m³/min compressor means that it
A. Compresses 3 m³/min of standard air
B. Compresses 3 m³/ min of free air
C. Delivers 3 m³/ min of compressed air
D. Delivers 3 m³/ min of compressed air at delivery pressure
Answer : B

48. Surging 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 : C

49. The efficiency of roots blower ________ with the increase in pressure ratio.
A. Decreases
B. Increases
C. Does not change
D. None of these
Answer : A

50. The assumption made in two stage compression with intercooler is that
A. There is no pressure drop in the intercooler
B. The compression in both the cylinders is polytropic
C. The suction and delivery of air takes place at constant pressure
D. All of the above
Answer : D