1000+ Compressors, Gas Turbines & Jet Engines MCQ for GATE [Solved]
Thursday 9th of March 2023
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1. As the turbine inlet temperature increases, the thermal efficiency of gas turbine for the optimum pressure ratio
A. Increases
B. Decreases
C. Remain same
D. First increases and then decreases
Answer : A
A. Increases
B. Decreases
C. Remain same
D. First increases and then decreases
Answer : A
2. 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
A. At very high speed
B. At very slow speed
C. At average speed
D. At zero speed
Answer : B
3. 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
A. Centrifugal type
B. Axial flow type
C. Radial flow type
D. None of these
Answer : B
4. 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
A. Same as isothermal
B. Same as adiabatic
C. Better than isothermal and adiabatic
D. In between isothermal and adiabatic
Answer : D
5. Losses in a centrifugal compressor are due to
A. Inlet losses
B. Impeller channel losses
C. Diffuser losses
D. All of the above
Answer : D
A. Inlet losses
B. Impeller channel losses
C. Diffuser losses
D. All of the above
Answer : D
6. 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
A. Inlet whirl velocity
B. Outlet whirl velocity
C. Inlet velocity of flow
D. Outlet velocity of flow
Answer : D
7. Which is false statement about multistage compression?
A. Power consumption per unit of air delivered is low
B. Volumetric efficiency is high
C. It is best suited for compression ratios around 7:1
D. The moisture in air is condensed in the intercooler
Answer : B
A. Power consumption per unit of air delivered is low
B. Volumetric efficiency is high
C. It is best suited for compression ratios around 7:1
D. The moisture in air is condensed in the intercooler
Answer : B
8. 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
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
9. 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
A. Gas turbine
B. 4-stroke petrol engine
C. 4-stroke diesel engine
D. Multi cylinder engine
Answer : A
10. 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
A. Compressor efficiency
B. Isentropic efficiency
C. Euler's efficiency
D. Pressure coefficient
Answer : D
11. Work ratio of a gas turbine may be improved by
A. Decreasing the compression work
B. Increasing the compression work
C. Increasing the turbine work
D. Both (A) and (C) above
Answer : D
A. Decreasing the compression work
B. Increasing the compression work
C. Increasing the turbine work
D. Both (A) and (C) above
Answer : D
12. The air power of the compressor is also known as
A. Indicated power
B. Brake power
C. Frictional power
D. None of these
Answer : A
A. Indicated power
B. Brake power
C. Frictional power
D. None of these
Answer : A
13. The workdone on a compressor will be minimum if air is taken from
A. The atmosphere
B. A source at 0°C
C. A source of low temperature air
D. A source of high temperature air
Answer : C
A. The atmosphere
B. A source at 0°C
C. A source of low temperature air
D. A source of high temperature air
Answer : C
14. 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
A. Blade camber
B. Blade camber and incidence angle
C. Spacechord ratio
D. Blade camber and spacechord ratio
Answer : B
15. A 3 m³/min compressor means that it
A. Compresses 3 m³/min of standard air
B. Compresses 3 m³/ min of free air
C. Delivers 3 m³/ min of compressed air
D. Delivers 3 m³/ min of compressed air at delivery pressure
Answer : B
A. Compresses 3 m³/min of standard air
B. Compresses 3 m³/ min of free air
C. Delivers 3 m³/ min of compressed air
D. Delivers 3 m³/ min of compressed air at delivery pressure
Answer : B
16. 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
A. Provides greater flexibility
B. Provides lesser flexibility
C. In never used
D. Is used when gas is to be burnt
Answer : A
17. 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
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
18. If infinite number of heaters be used in a gas turbine, then expansion process in turbine approaches
A. Isothermal
B. Isentropic
C. Adiabatic
D. Isochoric
Answer : A
A. Isothermal
B. Isentropic
C. Adiabatic
D. Isochoric
Answer : A
19. 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
A. Two times
B. Three times
C. Four times
D. Six times
Answer : D
20. Axial flow compressor resembles
A. Centrifugal pump
B. Reciprocating pump
C. Turbine
D. Sliding vane compressor
Answer : C
A. Centrifugal pump
B. Reciprocating pump
C. Turbine
D. Sliding vane compressor
Answer : C
21. 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
A. Less
B. More
C. Same
D. May be less or more depending on ambient conditions
Answer : A
22. 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
A. Requires less space for installation
B. Has compressor and combustion chamber
C. Has less efficiency
D. All of these
Answer : D
23. Isothermal compression efficiency, even when running at high speed, can be approached by using
A. Multistage compression
B. Cold water spray
C. Both (A) and (B) above
D. Fully insulating the cylinder
Answer : C
A. Multistage compression
B. Cold water spray
C. Both (A) and (B) above
D. Fully insulating the cylinder
Answer : C
24. The volumetric efficiency of a compressor falls roughly as follows for every 5°C increase in atmospheric temperature
A. 0.1 %
B. 0.5 %
C. 1 %
D. 5 %
Answer : C
A. 0.1 %
B. 0.5 %
C. 1 %
D. 5 %
Answer : C
25. Volumetric efficiency of a compressor without clearance volume
A. Increases with increase in compression ratio
B. Decreases with increase in compression ratio
C. Is not dependent upon compression ratio
D. May increase/decrease depending on compressor capacity
Answer : C
A. Increases with increase in compression ratio
B. Decreases with increase in compression ratio
C. Is not dependent upon compression ratio
D. May increase/decrease depending on compressor capacity
Answer : C
26. Maximum temperature in a gas turbine is of the order of
A. 700°C
B. 2000°C
C. 1500°C
D. 1000°C
Answer : A
A. 700°C
B. 2000°C
C. 1500°C
D. 1000°C
Answer : A
27. 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
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
28. In a closed cycle gas turbine, the air is compressed
A. Isothermally
B. Polytropically
C. Isentropically
D. None of these
Answer : C
A. Isothermally
B. Polytropically
C. Isentropically
D. None of these
Answer : C
29. Pick up the correct statement
A. Gas turbine uses low air-fuel ratio to economise on fuel
B. Gas turbine uses high air-fuel ratio to reduce outgoing temperature
C. Gas turbine uses low air-fuel ratio to develop the high thrust required
D. All of the above
Answer : B
A. Gas turbine uses low air-fuel ratio to economise on fuel
B. Gas turbine uses high air-fuel ratio to reduce outgoing temperature
C. Gas turbine uses low air-fuel ratio to develop the high thrust required
D. All of the above
Answer : B
30. 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
A. Constant volume
B. Constant temperature
C. Constant pressure
D. None of these
Answer : C
31. 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
A. 10 : 1
B. 15 : 1
C. 20 : 1
D. 60 : 1
Answer : D
32. 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
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
33. 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
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
34. 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
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
35. The following property is most important for material used for gas turbine blade
A. Toughness
B. Fatigue
C. Creep
D. Corrosion resistance
Answer : C
A. Toughness
B. Fatigue
C. Creep
D. Corrosion resistance
Answer : C
36. Work ratio of a gas turbine plant is ratio of
A. Net work output and work done by turbine
B. Net work output and heat supplied
C. Work done by turbine and heat supplied
D. Work done by turbine and net work output
Answer : A
A. Net work output and work done by turbine
B. Net work output and heat supplied
C. Work done by turbine and heat supplied
D. Work done by turbine and net work output
Answer : A
37. Pick up the correct statement
A. Large gas turbines use radial inflow turbines
B. Gas turbines have their blades similar to steam turbine
C. Gas turbine's blade will appear as impulse section at the hub and as a reaction section at tip
D. Gas turbines use both air and liquid cooling
Answer : C
A. Large gas turbines use radial inflow turbines
B. Gas turbines have their blades similar to steam turbine
C. Gas turbine's blade will appear as impulse section at the hub and as a reaction section at tip
D. Gas turbines use both air and liquid cooling
Answer : C
38. 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
A. Closed cycle
B. Open cycle
C. Both of the above
D. Closed/open depending on other considerations
Answer : A
39. 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
A. Equal to
B. Less than
C. More than
D. None of these
Answer : C
40. 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
A. Lower heating value
B. Higher heating value
C. Heating value
D. Higher calorific value
Answer : A
41. 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
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
42. Adiabatic compression is one in which
A. Temperature during compression remains constant
B. No heat leaves or enters the compressor cylinder during compression
C. Temperature rise follows a linear relationship
D. Work done is maximum
Answer : B
A. Temperature during compression remains constant
B. No heat leaves or enters the compressor cylinder during compression
C. Temperature rise follows a linear relationship
D. Work done is maximum
Answer : B
43. 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
A. 2 kg/cm²
B. 6 kg/cm²
C. 10 kg/cm²
D. 14.7 kg/cm²
Answer : A
44. 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
A. 75 %
B. 85 %
C. 90 %
D. 99 %
Answer : D
45. The maximum delivery pressure in a rotary air compressor is
A. 10 bar
B. 20 bar
C. 30 bar
D. 50 bar
Answer : A
A. 10 bar
B. 20 bar
C. 30 bar
D. 50 bar
Answer : A
46. 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
A. Equal to
B. Double
C. Three times
D. Six times
Answer : C
47. 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
A. Radial component
B. Axial component
C. Tangential component
D. None of the above
Answer : B
48. 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
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
49. An aftercooler is used to
A. Remove impurities from air
B. Reduce volume of air
C. Cause moisture and oil vapour to drop out
D. Cool the air
Answer : C
A. Remove impurities from air
B. Reduce volume of air
C. Cause moisture and oil vapour to drop out
D. Cool the air
Answer : C
50. The assumption made in two stage compression with intercooler is that
A. There is no pressure drop in the intercooler
B. The compression in both the cylinders is polytropic
C. The suction and delivery of air takes place at constant pressure
D. All of the above
Answer : D
A. There is no pressure drop in the intercooler
B. The compression in both the cylinders is polytropic
C. The suction and delivery of air takes place at constant pressure
D. All of the above
Answer : D
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