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Mechanical Engineering :: Compressors, Gas Turbines and Jet Engines

  1. The volumetric efficiency of a compressor falls roughly as follows for every 5°C increase in atmospheric temperature

  2. A.

     0.1%

    B.

     0.5%

    C.

     1%

    D.

     5%

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  3. The area of actual indicator diagram on an air compressor as compared to area of ideal indicator diagram is

  4. A.

     Less

    B.

     More

    C.

     Same

    D.

     More/less depending on compressor capacity

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  5. In a centrifugal compressor, the highest Mach number leading to shock wave in the fluid flow occurs at

  6. A.

     Diffuser inlet radius

    B.

     Diffuser outlet radius

    C.

     Impeller inlet radius

    D.

     Impeller outlet radius

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  7. If the clearance ratio for a reciprocating air compressor is 'K', then its volumetric efficiency is given by

  8. A.

     1 - k + k (p₁/p₂)1/n

    B.

     1 + k - k (p₂/p₁)1/n

    C.

     1 - k + k (p₁/p₂) n- 1/n

    D.

     1 + k - k (p₂/p₁) n-1/n

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  9. Axial flow compressor has the following advantage over centrifugal compressor

  10. A.

     Larger air handling ability per unit frontal area

    B.

     Higher pressure ratio per stage

    C.

     Aerofoil blades are used

    D.

     Higher average velocities

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  11. The pressure ratio of an ideal vaned compressor with increase in mass flow rate

  12. A.

     Increases

    B.

     Decreases

    C.

     Remain constant

    D.

     First decreases and then increases

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  13. The thermal efficiency of a simple gas turbine for a given turbine inlet temperature with increase in pressure ratio

  14. A.

     Increases

    B.

     Decreases

    C.

     First increases and then decreases

    D.

     First decreases and then increases

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  15. A closed cycle gas turbine consists of a

  16. A.

     Compressor

    B.

     Heating chamber

    C.

     Cooling chamber

    D.

     All of these

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  17. During base load operation, the best method of controlling compressor is

  18. A.

     Start-stop motor

    B.

     Constant speed unloader

    C.

     Relief valve

    D.

     Variable speed

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  19. The effective power of gas turbines is increased by adding the following in compressor

  20. A.

     Ammonia and water vapour

    B.

     Carbon dioxide

    C.

     Nitrogen

    D.

     Hydrogen

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