1000+ Compressors, Gas Turbines & Jet Engines Multiple Choice Question Answer [Solved]

1. The volume of air delivered by the compressor is called
A. Free air delivery
B. Compressor capacity
C. Swept volume
D. None of these
Answer : B

2. A rocket engine for the combustion of its fuel
A. Carries its own oxygen
B. Uses surrounding air
C. Uses compressed atmospheric air
D. Does not require oxygen
Answer : A

3. 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

4. A jet engine has
A. No propeller
B. Propeller in front
C. Propeller at back
D. Propeller on the top
Answer : A

5. For supplying intermittent small quantity of air at high pressure, following compressor is best suited
A. Centrifugal
B. Reciprocating
C. Axial
D. Screw
Answer : B

6. 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

7. The maximum combustion pressure in gas turbine as compared to I.C. engine is
A. More
B. Less
C. Same
D. Depends on other factors
Answer : B

8. The ratio of isentropic work to Eulers work is known as
A. Compressor efficiency
B. Isentropic efficiency
C. Euler's efficiency
D. Pressure coefficient
Answer : D

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

10. The pressure ratio for an open cycle gas turbine compared to closed cycle gas turbine of same h.p. is
A. Low
B. High
C. Same
D. Low/high depending on make and type
Answer : A

11. 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

12. 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

13. A rocket works with maximum overall efficiency when air craft velocity is equal to the
A. Jet velocity
B. Twice the jet velocity
C. Half the jet velocity
D. Average of the jet velocity
Answer : C

14. The inlet pressure is always ________ the discharge pressure.
A. Equal to
B. Less than
C. More than
D. None of these
Answer : B

15. The thermal efficiency of a simple gas turbine for a given turbine inlet temperature with increase in pressure ratio
A. Increases
B. Decreases
C. First increases and then decreases
D. First decreases and then increases
Answer : A

16. 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

17. 1 m of air at atmospheric condition weighs approximately
A. 0.5 kg
B. 1.0 kg
C. 1.3 kg
D. 2.2 kg
Answer : C

18. Gas turbine works on
A. Brayton or Atkinson cycle
B. Carnot cycle
C. Rankine cycle
D. Erricson cycle
Answer : A

19. The material commonly used for air craft gas turbine is
A. Stainless steel
B. High alloy steel
C. Duralumin
D. Timken, Haste alloys
Answer : D

20. In jet engines, paraffin is usually used as the fuel because of its
A. High calorific value
B. Ease of atomisation
C. Low freezing point
D. Both (A) and (C) above
Answer : D

21. In a jet engine, the air-fuel ratio is
A. 30 : 1
B. 40 : 1
C. 50 : 1
D. 60 : 1
Answer : D

22. The work ratio of a gas turbine plant is defined as the ratio of
A. Net work output and heat supplied
B. Net work output and work done by turbine
C. Actual heat drop and isentropic heat drop
D. Net work output and isentropic heat drop
Answer : B

23. 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

25. 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

26. In a centrifugal compressor, the flow of air is ________ to the axis of compressor.
A. Parallel
B. Perpendicular
C. Inclined
D. None of these
Answer : B

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

28. The pressure ratio of an ideal vaned compressor with increase in mass flow rate
A. Increases
B. Decreases
C. Remain constant
D. First decreases and then increases
Answer : C

29. 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

30. For perfect intercooling in a three stage compressor
A. p?/p? = p?/p? = p?/p?
B. p?/p? = p?/p?
C. p? p? = p? p?
D. p? p? = p? p?
Answer : A

31. Ratio of indicated h.p. to shaft h.p. in known as
A. Compressor efficiency
B. Isothermal efficiency
C. Volumetric efficiency
D. Mechanical efficiency
Answer : D

32. 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

33. Propulsive efficiency is defined as ratio of
A. Thrust power and fuel energy
B. Engine output and propulsive power
C. Propulsive power and fuel input
D. Thrust power and propulsive power
Answer : D

34. 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

35. 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

36. 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

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

38. Ram compression in turbojet involves
A. Reduction of speed of incoming air and conversion of part of it into pressure energy
B. Compression of inlet air
C. Increasing speed of incoming air
D. Lost work
Answer : A

39. 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

40. After-cooler is used to
A. Cool the air
B. Decrease the delivery temperature for ease in handling
C. Cause moisture and oil vapour to drop out
D. Reduce volume
Answer : C

41. Intercooling in gas turbines
A. Decreases net output but increases thermal efficiency
B. Increases net output but decreases thermal efficiency
C. Decreases net output and thermal efficiency both
D. Increases net output and thermal efficiency both
Answer : D

42. The maximum delivery pressure in a rotary air compressor is
A. 10 bar
B. 20 bar
C. 30 bar
D. 50 bar
Answer : A

43. 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

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

46. A compressor mostly used for supercharging of I.C. engines is
A. Radial flow compressor
B. Axial flow compressor
C. Roots blower
D. Reciprocating compressor
Answer : A

47. Air-fuel ratio in a jet engine will be of the order of
A. 10 : 1
B. 15 : 1
C. 20 : 1
D. 60 : 1
Answer : D

48. In axial flow compressor, exit flow angle deviation from the blade angle is a function of
A. Blade camber
B. Blade camber and incidence angle
C. Spacechord ratio
D. Blade camber and spacechord ratio
Answer : B

49. 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

50. In a single acting reciprocating compressor, the suction, compression and delivery of air takes place in ________ of the piston.
A. One stroke
B. Two strokes
C. Three strokes
D. Four strokes
Answer : B