Compressors, Gas Turbines & Jet Engines MCQ Solved Paper for SSC JE

1. In a single stage, single acting reciprocating air compressor without clearance volume, the workdone is maximum during
A. Isothermal compression
B. Isentropic compression
C. Polytropic compression
D. None of these
Answer : B

2. Axial flow compressor resembles
A. Centrifugal pump
B. Reciprocating pump
C. Turbine
D. Sliding vane compressor
Answer : C

3. 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

4. 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

5. 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

6. The efficiency of a jet engine is higher at
A. Low speeds
B. High speeds
C. Low altitudes
D. High altitudes
Answer : D

7. A jet engine works on the principle of conservation of
A. Mass
B. Energy
C. Flow
D. Linear momentum
Answer : D

8. 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

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

10. 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

11. 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

12. In a jet engine, the air-fuel ratio is
A. 30 : 1
B. 40 : 1
C. 50 : 1
D. 60 : 1
Answer : D

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

14. 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

15. 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

16. 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

17. The specific output per kg mass flow rate of a gas turbine (having fixed efficiencies of compressor and turbine and fixed higher and lower temperature) with increase in pressure ratio will
A. Increase first at fast rate and then slow
B. Increase first at slow rate and then fast
C. Decrease continuously
D. First increase, reach maximum and then decrease
Answer : D

18. 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

19. In a centrifugal compressor, the highest Mach number leading to shock wave in the fluid flow occurs at
A. Diffuser inlet radius
B. Diffuser outlet radius
C. Impeller inlet radius
D. Impeller outlet radius
Answer : B

20. 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

21. A closed gas turbine in which fuel is burnt directly in the air is not possible because of
A. Paucity of O2
B. Increasing gas temperature
C. High specific volume
D. High friction losses
Answer : A

22. The work ratio of simple gas turbine cycle depends on
A. Pressure ratio
B. Maximum cycle temperature
C. Minimum cycle temperature
D. All of the above
Answer : D

23. The compression ratio in a gas turbine is of the order of
A. 3.5 : 1
B. 5 : 1
C. 8 : 1
D. 12 : 1
Answer : C

24. 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

25. 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

26. 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

27. A compressor at high altitudes will require ________ power.
A. Same
B. Less
C. More
D. None of these
Answer : B

28. 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

29. The stagnation pressure rise in a centrifugal compressor takes place
A. In the diffuser only
B. In the impeller only
C. In the diffuser and impeller
D. In the inlet guide vanes only
Answer : C

30. In open cycle turbojet engines used in military aircraft, reheating the exhaust gas from the turbine by burning, more fuel is used to increase the
A. Thrust and range of aircraft
B. Efficiency of the engine
C. Both (A) and (B)
D. None of these
Answer : A

31. The compressor capacity is defined as the
A. Actual volume of the air delivered by the compressor when reduced to normal temperature and pressure conditions
B. Volume of air delivered by the compressor
C. Volume of air sucked by the compressor during its suction stroke
D. None of the above
Answer : B

32. 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

33. A machine used to raise the pressure of air is called
A. Gas turbine
B. I.C engine
C. Compressor
D. Air motor
Answer : C

34. Rotary 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 : B

35. 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

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

37. 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

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

39. A turboprop is preferred to turbojet because
A. It has high propulsive efficiency at high speeds
B. It can fly at supersonic speeds
C. It can fly at high elevations
D. It has high power for take off
Answer : D

40. 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

41. The axial flow compressor is preferred in aircraft gas turbines because of
A. Low frontal area
B. Higher thrust
C. High pressure rise
D. None of these
Answer : A

42. 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

43. 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

44. The volume of air delivered in a medium capacity air compressor per unit time is
A. 0.1 to 1.2 m³/s
B. 0.15 to 5 m³/s
C. Above 5 m³/s
D. None of these
Answer : B

45. 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

46. 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

47. 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

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

49. In a single acting reciprocating air compressor, without clearance, the compression of air may be
A. Isothermal
B. Polytropic
C. Isentropic
D. Any one of these
Answer : D

50. 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