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Mechanical Engineering :: Compressors, Gas Turbines and Jet Engines

  1. The pressure and temperature conditions of air at the suction of compressor are

  2. A.

     Atmospheric

    B.

     Slightly more than atmospheric

    C.

     Slightly less than atmospheric

    D.

     Pressure slightly less than atmospheric and temperature slightly more than atmospheric

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  3. If p₁, is the pressure of air entering the L.P. cylinder and p₂ is the pressure of air leaving the L.P. cylinder (or inter-cooler pressure), then the ratio of cylinder diameters for a single acting, two stage reciprocating air compressor with complete intercooling is given by (where D₁ = Dia. of L.P. cylinder, and D₂ = Dia. of H.P. cylinder)

  4. A.

     D₁/D₂ = p₁ p₂

    B.

     D₁/D₂ = p₁/p₂

    C.

     D₁/D₂ = p₂/p₁

    D.

     None of these

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  5. In n₁ and n₂ are the indices of compression for the first and second stage of compression, then the ratio of work-done on the first and second stages (W₁/W₂) with perfect intercooling is given by

  6. A.

     W₁/W₂ = n₂(n₁ - 1)/n₁(n₂ - 1)

    B.

     W₁/W₂ = n₁(n₂ - 1)/n₂(n₁ - 1)

    C.

     W₁/W₂ = n₁/n₂

    D.

     W₁/W₂ = n₂/n₁

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  7. If p₁ is the pressure of air entering the L.P, cylinder and p₃ is the pressure of air leaving the H.P. cylinder, then the ratio of cylinder diameters for a single acting, two stage reciprocating compressor with complete intercooling is given by

  8. A.

     D₁/D₂ = (p₁ p₃)1/2

    B.

     D₁/D₂ = (p₁/p₃)1/4

    C.

     D₁/D₂ = (p₁ p₃)1/4

    D.

     D₁/D₂ = (p₃/p₁)1/4

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  9. Volumetric efficiency of a compressor decreases with ________ in compression ratio.

  10. A.

     Decrease

    B.

     Increase

    C.

     Remain same

    D.

     Does not change

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  11. In multistage compressor, the isothermal compression is achieved by

  12. A.

     Employing inter-cooler

    B.

     By constantly cooling the cylinder

    C.

     By running compressor at very slow speed

    D.

     By insulating the cylinder

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  13. In a single stage, single acting reciprocating air compressor, without clearance, the work-done on the air during isentropic compression is ________ the heat required to raise the temperature of air from T₁ to T₂ at a constant pressure.

  14. A.

     Equal to

    B.

     Less than

    C.

     Greater than

    D.

     None of these

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  15. Out of the following, from where you will prefer to take intake for air compressor

  16. A.

     From an air conditioned room maintained at 20°C

    B.

     From outside atmosphere at 1°C

    C.

     From coal yard side

    D.

     From a side where cooling tower is located nearby

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  17. For supplying intermittent small quantity of air at high pressure, following compressor is best suited

  18. A.

     Centrifugal

    B.

     Reciprocating

    C.

     Axial

    D.

     Screw

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  19. The thrust on the rotor in a centrifugal compressor is produced by

  20. A.

     Radial component

    B.

     Axial component

    C.

     Tangential component

    D.

     None of the above

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