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Mechanical Engineering :: Compressors, Gas Turbines and Jet Engines

  1. Propulsion efficiency of the following order is obtained in practice

  2. A.

     34%

    B.

     50%

    C.

     60%

    D.

     72%

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  3. The maximum delivery pressure in a rotary air compressor is

  4. A.

     10 bar

    B.

     20 bar

    C.

     30 bar

    D.

     50 bar

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  5. In a closed cycle gas turbine, the air is compressed

  6. A.

     Isothermally

    B.

     Polytropically

    C.

     Isentropically

    D.

     None of these

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  7. In a double acting compressor, the air is compressed

  8. A.

     In one cylinder

    B.

     In two cylinders

    C.

     In a single cylinder on both sides of the piston

    D.

     In two cylinders on both sides of the piston

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  9. The work-done on a compressor will be minimum if air is taken from

  10. A.

     The atmosphere

    B.

     A source at 0° C

    C.

     A source of low temperature air

    D.

     A source of high temperature air

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  11. Free air is the air at

  12. A.

     Atmospheric conditions at any specific location

    B.

     20°C and 1 kg/cm² and relative humidity of 36%

    C.

     0°C and standard atmospheric conditions

    D.

     15°C and 1 kg/cm²

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  13. Standard air is the air at

  14. A.

     Atmospheric conditions at any specific location

    B.

     20°C and 1 kg/cm² and relative humidity 36%

    C.

     0°C and standard atmospheric conditions

    D.

     15°C and 1 kg/cm²

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  15. The overall efficiency of the compressed air system is the

  16. 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

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  17. In a jet engine, the air-fuel ratio is

  18. A.

     30:1

    B.

     40:1

    C.

     50:1

    D.

     60:1

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  19. The reason for volumetric efficiency of reciprocating compressor being less than 100 percent is

  20. A.

     Pressure drop across the valves

    B.

     Superheating in compressor

    C.

     Clearance volume and leakages

    D.

     All of these

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