1000+ Compressors, Gas Turbines & Jet Engines MCQ for SSC JHT [Solved]

1. In a compressor, free air delivered is the actual volume delivered at the stated pressure reduced to
A. N.T.P. conditions
B. Intake temperature and pressure conditions
C. 0°C and 1 kg/cm²
D. 20°C and 1 kg/cm²
Answer : B

2. In the aircraft propellers
A. The propulsive matter is caused to flow around the propelled body
B. Propulsive matter is ejected from within the propelled body
C. Its functioning does not depend on presence of air
D. All of the above
Answer : D

3. 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

4. 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

5. 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

6. Atmospheric pressure is 1.03 kg/cm and vapour pressure is 0.03 kg/cm. The air pressure will be
A. 1.03 kg/cm²
B. 1.06 kg/cm²
C. 1.00 kg/cm²
D. 0.53 kg/cm²
Answer : C

7. 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

8. 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

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

10. 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

11. 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

12. 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

13. 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

14. In n? and n? are the indices of compression for the first and second stage of compression, then the ratio of workdone on the first and second stages (W?/W?) with perfect intercooling is given by
A. W?/W? = n?(n? - 1)/n?(n? - 1)
B. W?/W? = n?(n? - 1)/n?(n? - 1)
C. W?/W? = n?/n?
D. W?/W? = n?/n?
Answer : B

15. 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

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

17. 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

18. 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

19. In the cross compounding of the gas turbine plant
A. H.P. compressor is connected to H.P. turbine and L.P. compressor to L.P. turbine
B. H.P. compressor is connected to L.P. turbine and L.P. compressor is connected to H.P. turbine
C. Both the arrangements can be employed
D. All are connected in series
Answer : B

20. The intercooler pressure, for minimum work required, for a two stage reciprocatin 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

21. 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

22. 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

23. 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

24. 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

25. The degree of reaction of an axial flow turbine is the ratio of isentropic temperature drop in a blade row to the
A. Adiabatic temperature drop in the stage
B. Total temperature drop
C. Total temperature drop in the stage
D. Total adiabatic temperature drop
Answer : C

26. 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

27. 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

28. 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

29. A centrifugal compressor works on the principle of
A. Conversion of pressure energy into kinetic energy
B. Conversion of kinetic energy into pressure energy
C. Centripetal action
D. Generating pressure directly
Answer : B

30. 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

31. 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

32. 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

33. 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

34. 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

35. An ideal air compressor cycle without 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 : A

36. A large clearance volume in a reciprocating compressor results in
A. Reduced volume flow rate
B. Increased volume flow rate
C. Lower suction pressure
D. Lower delivery pressure
Answer : A

37. The ratio of the increase in pressure in rotor blades to total increase in pressure in the stage is called
A. Pressure ratio
B. Pressure coefficient
C. Degree of reaction
D. Slip factor
Answer : C

38. In air breathing jet engine, the jet is formed by expanding
A. Highly heated atmospheric air
B. Solids
C. Liquid
D. Plasma
Answer : A

39. 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

40. 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

41. For minimum work in multistage compression, assuming same index of compression in all stages
A. Work done in first stage should be more
B. Work done in subsequent stages should increase
C. Work done in subsequent stages should decrease
D. Work done in all stages should be equal
Answer : D

42. 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

43. 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

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

45. 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

46. 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

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

48. 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

49. During base load operation, the best method of controlling compressor is
A. Start-stop motor
B. Constant speed unloader
C. Relief valve
D. Variable speed
Answer : A

50. The compressed air may be used
A. In gas turbine plants
B. For operating pneumatic drills
C. In starting and supercharging of I.C. engines
D. All of the above
Answer : D