Compressors, Gas Turbines & Jet Engines MCQ Solved Paper for NEET PG

1. The temperature of air at the beginning of the compression stroke is ________ the atmospheric temperature.
A. Equal to
B. Less than
C. More than
D. None of these
Answer : C

2. In a closed cycle gas turbine, the air is compressed
A. Isothermally
B. Polytropically
C. Isentropically
D. None of these
Answer : C

3. 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

4. The pressure of air at the beginning of the compression stroke is ________ the atmospheric pressure.
A. Equal to
B. Less than
C. More than
D. None of these
Answer : B

5. The ratio of the indicated power to the shaft power or brake power of the motor or engine required to drive the compressor, is called
A. Compressor efficiency
B. Volumetric efficiency
C. Isothermal efficiency
D. Mechanical efficiency
Answer : D

6. 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

7. The degree of reaction in an axial flow compressor is defined as the ratio of static enthalpy rise in the
A. Rotor to static enthalpy rise in the stator
B. Stator to static enthalpy rise in the rotor
C. Rotor to static enthalpy rise in the stage
D. Stator to static enthalpy rise in the stage
Answer : C

8. Pick up the correct statement
A. Closed cycle gas turbine is an I.C engine
B. Gas turbine uses same working fluid over and over again
C. Ideal efficiency of closed cycle gas turbine plant is more than Carnot cycle efficiency
D. Thrust in turbojet is produced by nozzle exit gases.
Answer : D

9. 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

10. 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

11. 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

12. In jet propulsion power unit, the inlet duct of diverging shape is used in order to
A. Collect more air
B. Convert kinetic energy of air into pressure energy
C. Provide robust structure
D. Beautify the shape
Answer : B

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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

23. Out of the following, from where you will prefer to take intake for air compressor
A. From an air conditioned room maintained at 20°C
B. From outside atmosphere at 1°C
C. From coal yard side
D. From a side where cooling tower is located nearby
Answer : D

24. In gas turbines, high thermal efficiency is obtained in
A. Closed cycle
B. Open cycle
C. Both of the above
D. Closed/open depending on other considerations
Answer : A

25. Pick up the wrong statement
A. Pulsejet requires no ambient air for propulsion
B. Ramjet engine has no turbine
C. Turbine drives compressor in a Turbojet
D. Bypass turbojet engine increases the thrust without adversely affecting, the propulsive efficiency and fuel economy
Answer : A

26. 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

27. In a centrifugal compressor, an increase in speed at a given pressure ratio causes
A. Increase in flow
B. Decrease in flow
C. Increase in efficiency
D. Increase in flow and decrease in efficiency
Answer : D

28. The effective power of gas turbines is increased by adding the following in compressor
A. Ammonia and water vapour
B. Carbon dioxide
C. Nitrogen
D. Hydrogen
Answer : A

29. 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

30. 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

31. 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

32. Water 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, eke, anthracite coal or charcoal in a mixed air steam blast
Answer : B

33. 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

34. 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

35. A closed cycle gas turbine consists of a
A. Compressor
B. Heating chamber
C. Cooling chamber
D. All of these
Answer : D

36. 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

37. 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

38. In multistage compressor, the isothermal compression is achieved by
A. Employing intercooler
B. By constantly cooling the cylinder
C. By running compressor at very slow speed
D. By insulating the cylinder
Answer : C

39. A rotary compressor is driven by an
A. Electric motor
B. Engine
C. Either (A) or (B)
D. None of these
Answer : C

40. The following property is most important for material used for gas turbine blade
A. Toughness
B. Fatigue
C. Creep
D. Corrosion resistance
Answer : C

41. 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

42. 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

43. 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

44. 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

45. 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

46. 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

47. The criterion of the thermodynamic efficiency for rotary compressor is
A. Isentropic compression
B. Isothermal compression
C. Polytropic compression
D. None of the above
Answer : A

48. The air is delivered ________ in one revolution in case of a three lobbed rotor.
A. Two times
B. Three times
C. Four times
D. Six times
Answer : D

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

50. The compressor efficiency is the
A. Isothermal H.P/indicated H.R
B. Isothermal H.P./shaft H.R
C. Total output/air input
D. Compression work/motor input
Answer : A