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

1. 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

2. Which is false statement about air receivers?
A. These are used to dampen pulsations
B. These act as reservoir to take care of sudden demands
C. These increase compressor efficiency
D. These knock out some oil and moisture
Answer : C

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

4. 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

5. 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

6. A closed cycle gas turbine works on
A. Carnot cycle
B. Rankine cycle
C. Ericsson cycle
D. Joule cycle
Answer : D

7. 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

8. 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

9. 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

10. During peak load periods, the best method of controlling compressors is
A. Start-stop motor
B. Constant speed unloader
C. Relief valve
D. Variable speed
Answer : B

11. 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

12. 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

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

14. In a single stage, single acting reciprocating air compressor, without clearance, the workdone on the air during isentropic compression is ________ the heat required to raise the temperature of air from T? to T? at a constant pressure.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : A

15. Propulsive efficiency is defined as ratio of
A. Thrust power and fuel energy
B. Engine output and propulsive power
C. Propulsive power and fuel input
D. Thrust power and propulsive power
Answer : D

16. The thermal efficiency of a gas turbine as compared to a diesel plant is
A. Same
B. More
C. Less
D. Depends on other factors
Answer : C

17. 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

18. 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

19. The blades of gas turbine are made of
A. High nickel alloy
B. Stainless steel
C. Carbon steel
D. High alloy steel
Answer : A

20. 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

21. 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

22. The ratio of the volume of free air delivery per stroke to the swept volume of the piston, is known as
A. Compressor efficiency
B. Volumetric efficiency
C. Isothermal efficiency
D. Mechanical efficiency
Answer : B

23. 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

24. 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

25. 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

26. 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

27. The overall isothermal efficiency of the compressor is defined as the ratio of
A. Work required to compress the air isothermally to the actual work required to compress the air for the same pressure ratio
B. Isothermal power to the shaft power or B.P. of the motor or engine required to drive the compressor
C. Volume of free air delivery per stroke to the swept volume of the piston
D. Isentropic power to the power required to drive the compressor
Answer : B

28. 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

29. The thrust of a jet propulsion power unit can be increased by
A. Injecting water into the compressor
B. Burning fuel after gas turbine
C. Injecting ammonia into the combustion chamber
D. All of the above
Answer : D

30. For speed above 3000 km/hour, it is more advantageous to use
A. Turbojet engine
B. Ramjet engine
C. Propellers
D. Rockets
Answer : B

31. 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

32. 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

33. The volumetric efficiency for reciprocating air compressors is about
A. 10 to 40 %
B. 40 to 60 %
C. 60 to 70 %
D. 70 to 90 %
Answer : D

34. The capacity of a compressor is 5 m /min refers to
A. Standard air
B. Free air
C. Compressed air
D. Compressed air at delivery pressure
Answer : B

35. 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

36. 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

37. 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

38. 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

39. The degree of reaction is usually kept ________ for all types of axial flow compressors.
A. 0.2
B. 0.3
C. 0.4
D. 0.5
Answer : D

40. The inlet pressure is always ________ the discharge pressure.
A. Equal to
B. Less than
C. More than
D. None of these
Answer : B

41. 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

42. Gas turbines use following type of air compressor
A. Centrifugal type
B. Reciprocating type
C. Lobe type
D. Axial flow type
Answer : D

43. 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

44. For slow speed large capacity compressor, following type of valve will be best suited
A. Poppet valve
B. Mechanical valve of the Corliss, sleeve, rotary or semi rotary type
C. Disc or feather type
D. Any of the above
Answer : C

45. The main purpose of reheating in gas turbine is to
A. Increase temperature
B. Reduce turbine size
C. Increase power output
D. Increase speed
Answer : C

46. 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

47. 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

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. To avoid moisture troubles, the compressed air main line should
A. Rise gradually towards the point of use
B. Drop gradually towards the point of use
C. Be laid vertically
D. Be laid exactly horizontally
Answer : B

50. A compressor at high altitude will draw
A. More power
B. Less power
C. Same power
D. More/less power depending on other factors
Answer : B