LSAT - Compressors, Gas Turbines & Jet Engines 1000+ MCQ [Solved] PDF Download

1. 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

2. For minimum work required to compress and deliver a quantity of air by multistage compression
A. The compression ratio in each stage should be same
B. The intercooling should be perfect
C. The workdone in each stage should be same
D. All of the above
Answer : D

3. 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

4. Choose the correct statement
A. Gas turbine requires lot of cooling water
B. Gas turbine is capable of rapid start up and loading
C. Gas turbines has flat efficiency at part loads
D. Gas turbines have high standby losses and require lot of maintenance
Answer : B

5. 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

6. An ideal air compressor cycle with clearance on PV diagram can be represented by following processes
A. One adiabatic, two isobaric, and one constant volume
B. Two adiabatic and two isobaric
C. Two adiabatic, one isobaric and one constant volume
D. One adiabatic, one isobaric and two constant volumes
Answer : B

7. 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

8. 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

9. 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

10. 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

11. 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

12. Which of the following statement is correct?
A. The ratio of the discharge pressure to the inlet pressure of air is called compressor efficiency
B. The compression ratio for the compressor is always greater than unity
C. The compressor capacity is the ratio of workdone per cycle to the stroke volume
D. During isothermal compression of air, the workdone in a compressor is maximum
Answer : B

13. 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

14. 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

15. 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

16. 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

17. The power available for takeoff and climb in case of turbojet engine as compared to reciprocating engine is
A. Less
B. More
C. Same
D. May be less or more depending on ambient conditions
Answer : A

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. 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

20. For maximum work, the reheating should be done to an intermediate pressure of (Where p? = Maximum pressure, and p? = Minimum pressure)
A. (p? - p?)/2
B. (p? + p?)/2
C. p?/p?
D. p? p?
Answer : D

21. In a centrifugal compressor, the ratio of the ________ to the blade velocity is called slip factor.
A. Inlet whirl velocity
B. Outlet whirl velocity
C. Inlet velocity of flow
D. Outlet velocity of flow
Answer : D

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

23. The weight per horse power ratio for gas in Turbine as compared to I.C. engine and steam turbine is
A. Same
B. Higher
C. Lower
D. None of these
Answer : C

24. The thrust on the rotor in a centrifugal compressor is produced by
A. Radial component
B. Axial component
C. Tangential component
D. None of the above
Answer : B

25. 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

26. 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

27. In the axial flow gas turbine, the work ratio is the ratio of
A. Compressor work and turbine work
B. Output and input
C. Actual total head temperature drop to the isentropic total head drop from total head inlet to static head outlet
D. Actual compressor work and theoretical compressor work
Answer : C

28. When air is to be compressed at a high pressure, then it is advantageous to use
A. Single stage compression
B. Multistage compression without intercooling
C. Multistage compression with intercooling
D. None of these
Answer : C

29. Which of the following fuels can be used in turbojet engines?
A. Liquid hydrogen
B. High speed diesel oil
C. Kerosene
D. Methyl alcohol
Answer : C

30. 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

31. The volumetric efficiency of a compressor falls roughly as follows for every 100 m increase in elevation
A. 0.1 %
B. 0.5 %
C. 1.0 %
D. 5 %
Answer : C

32. 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

33. 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

34. Fighter bombers use following type of engine
A. Turbojet
B. Turbo-propeller
C. Rocket
D. Ramjet
Answer : A

35. 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

36. The working fluid in a turbine is
A. In two phases
B. In three phases
C. In a single phase
D. In the form of air and water mixture
Answer : C

37. 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

38. 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

39. 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

40. When the outlet angle from the rotor of a centrifugal compressor is more than 90°, then the blades are said to be
A. Forward curved
B. Backward curved
C. Radial
D. None of these
Answer : A

41. 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

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

43. 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

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

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

46. 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

47. Gas turbine as compared to internal combustion engine
A. Can be driven at a very high speed
B. Produces uniform torque
C. Has more efficiency
D. All of these
Answer : D

48. 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

49. Gas turbine blades are given a rake
A. Equal to zero
B. In the direction of motion of blades
C. Opposite to the direction of motion of blades
D. Depending on the velocity
Answer : B

50. In which case the air-fuel ratio is likely to be maximum?
A. Gas turbine
B. 4-stroke petrol engine
C. 4-stroke diesel engine
D. Multi cylinder engine
Answer : A