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

1. 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

2. Mechanical efficiency of gas turbines as compared to I.C engines is
A. Higher
B. Lower
C. Same
D. None of the above
Answer : A

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

4. More than one stage will be preferred for reciprocating compressor if the delivery pressure is more than
A. 2 kg/cm²
B. 6 kg/cm²
C. 10 kg/cm²
D. 14.7 kg/cm²
Answer : A

5. The ratio of the net work obtained from the gas turbine plant to the turbine work is known as
A. Compression ratio
B. Work ratio
C. Pressure ratio
D. None of these
Answer : B

6. 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

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

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. Aeroplanes employ following type of compressor
A. Radial flow
B. Axial flow
C. Centrifugal
D. None of the above
Answer : B

10. 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

11. The propulsive power of the rocket is (where v? = Jet velocity, and v? = Aircraft velocity)
A. (v?² -v?²)/2g
B. (v? - v?)²/2g
C. (v?² -v?²)/g
D. (v? - v?)²/g
Answer : A

12. There is a certain pressure ratio (optimum) for a gas turbine at which its thermal efficiency is maximum. With increase in turbine temperature, the value of pressure ratio for the peak efficiency would
A. Remain same
B. Decrease
C. Increase
D. None of the above
Answer : C

13. 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

14. If p? is the pressure of air entering the L.P, cylinder and p? is the pressure of air leaving the H.P. cylinder, then the ratio of cylinder diameters for a single acting, two stage reciprocating compressor with complete intercooling is given by
A. D?/D? = (p? p?)^1/2
B. D?/D? = (p?/p?)^1/4
C. D?/D? = (p? p?)^1/4
D. D?/D? = (p?/p?)^1/4
Answer : D

15. 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

16. 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

17. 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

18. 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

19. 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

20. In a jet propulsion unit, the products of combustion after passing through the gas turbine are discharged into
A. Atmosphere
B. Vacuum
C. Discharge nozzle
D. Back to the compressor
Answer : C

21. 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

22. 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

23. 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

24. Rotary compressors are suitable for
A. Large discharge at high pressure
B. Low discharge at high pressure
C. Large discharge at low pressure
D. Low discharge at low pressure
Answer : C

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

26. 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

27. 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

28. 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

29. Volumetric efficiency of air compressors is of the order of
A. 20 - 30 %
B. 40 - 50 %
C. 60 - 70 %
D. 70 - 90 %
Answer : D

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

31. 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

32. 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

33. Pick up the false statement
A. Gas turbine is a self starting unit
B. Gas turbine does not require huge quantity of water like steam plant
C. Exhaust losses in gas turbine are high due to large mass flow rate
D. Overall efficiency of gas turbine plant is lower than that of a reciprocating engine
Answer : A

34. In a double acting compressor, the air is compressed
A. In one cylinder
B. In two cylinders
C. In a single cylinder on both sides of the piston
D. In two cylinders on both sides of the piston
Answer : C

35. 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

36. 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

37. The volumetric efficiency of a compressor
A. Increases with decrease in compression ratio
B. Decreases with decrease in compression ratio
C. Increases with increase in compression ratio
D. Decreases with increase in compression ratio
Answer : D

38. 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

39. 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

40. 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

41. 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

42. The ratio of workdone per cycle to the stroke volume of the compressor is known as
A. Compressor capacity
B. Compression ratio
C. Compressor efficiency
D. Mean effective pressure
Answer : D

43. High air-fuel ratio in gas turbines
A. Increases power output
B. Improves thermal efficiency
C. Reduces exhaust temperature
D. Do not damage turbine blades
Answer : C

44. 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

45. 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

46. 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

47. The minimum work required for a three stage reciprocating air compressor is ________ the work required for each stage.
A. Equal to
B. Double
C. Three times
D. Six times
Answer : C

48. 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

49. 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

50. 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