asportzone.com – MCQs, Mock Tests | Engineering Compressors, Gas Turbines and Jet Engines MCQ Practice Test

1 With the decrease in compression ratio, the volumetric efficiency

A Does not change B Increases C Decreases D First decrease and then increase

✅ Correct Answer: 2

2 Pick up wrong statement. Surging phenomenon in centrifugal compressor depends on

A Mass flow rate B Pressure ratio C Change in load D Stagnation pressure at the outlet

✅ Correct Answer: 4

3 In air compressors, free air delivery means 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

✅ Correct Answer: 1

4 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

✅ Correct Answer: 3

5 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

✅ Correct Answer: 4

6 Axial flow compressor resembles

A Centrifugal pump B Reciprocating pump C Turbine D Sliding vane compressor

✅ Correct Answer: 3

7 The efficiency of roots blower ________ with the increase in pressure ratio.

A Decreases B Increases C Does not change D None of these

✅ Correct Answer: 1

8 Axial flow compressor has the following advantage over centrifugal compressor

A Larger air handling ability per unit frontal area B Higher pressure ratio per stage C Aerofoil blades are used D Higher average velocities

✅ Correct Answer: 1

9 The maximum temperature in a gas turbine is

A 200Â°C B 500Â°C C 700Â°C D 1000Â°C

✅ Correct Answer: 3

10 Actual compression curve is

A Same as isothermal B Same as adiabatic C Better than isothermal and adiabatic D In between isothermal and adiabatic

✅ Correct Answer: 4

11 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

✅ Correct Answer: 4

12 Atmospheric pressure is 1.03 kg/cm and vapour pressure is 0.03 kg/cm. The air pressure will be

A 1.03 kg/cmÂ² B 1.06 kg/cmÂ² C 1.00 kg/cmÂ² D 0.53 kg/cmÂ²

✅ Correct Answer: 3

13 For maximum work, the reheating should be done to an intermediate pressure of (Where pâ‚ = Maximum pressure, and pâ‚‚ = Minimum pressure)

A (pâ‚ - pâ‚‚)/2 B (pâ‚ + pâ‚‚)/2 C pâ‚/pâ‚‚ D pâ‚ pâ‚‚

✅ Correct Answer: 4

14 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

✅ Correct Answer: 3

15 If the flow of air through the compressor is parallel to its axis, then the compressor is

A Reciprocating compressor B Centrifugal compressor C Axial flow compressor D Turbo compressor

✅ Correct Answer: 3

16 A compressor at high altitudes will require ________ power.

A Same B Less C More D None of these

✅ Correct Answer: 2

17 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

✅ Correct Answer: 4

18 The compression ratio for the compressor is always _________ unity.

A Equal to B Less than C More than D None of these

✅ Correct Answer: 3

19 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

✅ Correct Answer: 2

20 Euler's equation can be used for

A Radial flow compressors B Axial flow compressors C Pumps D All of the above

✅ Correct Answer: 4

21 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

✅ Correct Answer: 4

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

✅ Correct Answer: 4

23 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

✅ Correct Answer: 4

24 The efficiency of a jet engine is higher at

A Low speeds B High speeds C Low altitudes D High altitudes

✅ Correct Answer: 4

25 The pressure ratio for an open cycle gas turbine compared to closed cycle gas turbine of same h.p. is

A Low B High C Same D Low/high depending on make and type

✅ Correct Answer: 1

26 In a single acting reciprocating compressor, the suction, compression and delivery of air takes place in ________ of the piston. (A) One stroke (B) Two strokes (C) (D)

A One stroke B Two strokes C Three strokes D Four strokes

✅ Correct Answer: 2

27 Open cycle gas turbine works on (A)

A Brayton or Atkinson cycle B Rankine cycle C Carnot cycle D Ericsson cycle

✅ Correct Answer: 1

28 Which of the following statement is wrong?

A In a two stage reciprocating air compressor with complete intercooling, maximum work is saved B The minimum work required for a two stage reciprocating air compressor is double the work required for each stage C The ratio of the volume of free air delivery per stroke to the swept volume of the piston is called volumetric efficiency D None of the above

✅ Correct Answer: 4

29 Which of the following statement is wrong?

A In a two stage reciprocating air compressor with complete intercooling, maximum work is saved B The minimum work required for a two stage reciprocating air compressor is double the work required for each stage C The ratio of the volume of free air delivery per stroke to the swept volume of the piston is called volumetric efficiency D None of these

✅ Correct Answer: 4

30 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

✅ Correct Answer: 1

31 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

✅ Correct Answer: 3

32 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

✅ Correct Answer: 4

33 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

✅ Correct Answer: 3

34 A large clearance volume in a reciprocating compressor results in

A Increased volume flow rate B Reduced volume flow rate C Lower suction pressure D Lower delivery pressure

✅ Correct Answer: 1

35 The air-fuel ratio in gas turbines is of the order of

A 7: 1 B 15: 1 C 30: 1 D 50: 1.

✅ Correct Answer: 4

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 minimize the work of compression

✅ Correct Answer: 4

37 The pressure ratio in gas turbines is of the order of

A 2: 1 B 4:1 C 61: 1 D 9: 1

✅ Correct Answer: 3

38 An after-cooler 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

✅ Correct Answer: 4

39 When the outlet angle from the rotor of a centrifugal compressor is more than 90Â°, then the blades are said to be

A Forward curved B Backward curved C Radial D None of these

✅ Correct Answer: 1

40 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

✅ Correct Answer: 2

41 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

✅ Correct Answer: 2

42 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

✅ Correct Answer: 2

43 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

✅ Correct Answer: 2

44 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

✅ Correct Answer: 2

45 The inlet pressure is always ________ the discharge pressure.

A Equal to B Less than C More than D None of these

✅ Correct Answer: 2

46 The inlet pressure is always ________ the discharge pressure.

A Equal to B Less than C More than D None of these

✅ Correct Answer: 2

47 The inlet pressure is always ________ the discharge pressure.

A Equal to B Less than C More than D None of these

✅ Correct Answer: 2

48 The inlet pressure is always ________ the discharge pressure.

A Equal to B Less than C More than D None of these

✅ Correct Answer: 2

49 The inlet pressure is always ________ the discharge pressure.

A Equal to B Less than C More than D None of these

✅ Correct Answer: 2

50 The inlet pressure is always ________ the discharge pressure.

A Equal to B Less than C More than D None of these

✅ Correct Answer: 2

51 Temperature of gases at end of compression as compared to exhaust gases in a gas turbine is

A Higher B Lower C Equal D Canâ€™t be compared

✅ Correct Answer: 2

52 The volume of air delivered by the compressor is called

A Free air delivery B Compressor capacity C Swept volume D None of these

✅ Correct Answer: 2

53 A jet engine has

A No propeller B Propeller in front C Propeller at back D Propeller on the top

✅ Correct Answer: 1

54 The material commonly used for air craft gas turbine is

A Stainless steel B High alloy steel C Duralumin D Timken, Haste alloys

✅ Correct Answer: 4

55 The material commonly used for air craft gas turbine is

A Stainless steel B High alloy steel C Duralumin D Timken, Haste alloys

✅ Correct Answer: 4

56 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

✅ Correct Answer: 1

57 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

✅ Correct Answer: 3

58 The combustion efficiency of a gas turbine using perfect combustion chamber is of the order of

A 75% B 85% C 90% D 99%

✅ Correct Answer: 4

59 For an irreversible gas turbine cycle, the efficiency and work ratio both depend on

A Pressure ratio alone B Maximum cycle temperature alone C Minimum cycle temperature alone D Both pressure ratio and maximum cycle temperature

✅ Correct Answer: 4

60 Separators are generally used in air compressor installations

A Before the inter-cooler B After the inter-cooler C Between the after-cooler and receiver D Before first stage suction

✅ Correct Answer: 3

61 Producer 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 65Â°C D Partial combustion of coal, coke, anthracite coal or charcoal in a mixed air steam blast

✅ Correct Answer: 4

62 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 65Â°C D Partial combustion of coal, eke, anthracite coal or charcoal in a mixed air steam blast

✅ Correct Answer: 2

63 In a single stage, single acting reciprocating air compressor without clearance volume, the work-done is maximum during

A Isothermal compression B Isentropic compression C Polytropic compression D None of these

✅ Correct Answer: 2

64 Water is injected in gas turbine cycle to

A Control temperature B Control output of turbine C Control fire hazards D Increase efficiency

✅ Correct Answer: 2

65 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.

✅ Correct Answer: 2

66 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%

✅ Correct Answer: 4

67 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

✅ Correct Answer: 3

68 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

✅ Correct Answer: 3

69 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

✅ Correct Answer: 2

70 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

✅ Correct Answer: 1

71 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

✅ Correct Answer: 1

72 Choose the correct statement

A Gas turbine requires lot of cooling water B Gas turbine is capable of rapid start up and loading C Gas turbines has flat efficiency at part loads D Gas turbines have high standby losses and require lot of maintenance

✅ Correct Answer: 2

73 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

✅ Correct Answer: 2

74 A jet engine works on the principle of conservation of

A Mass B Energy C Flow D Linear momentum

✅ Correct Answer: 4

75 Which of the following fuels can be used in turbojet engines?

A Liquid hydrogen B High speed diesel oil C Kerosene D Methyl alcohol

✅ Correct Answer: 3

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Compressors, Gas Turbines and Jet Engines MCQ Practice Test - Set 03