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Mechanical Engineering :: Compressors, Gas Turbines and Jet Engines

  1. Which of the following statement is correct?

  2. 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 work-done per cycle to the stroke volume

    D.

     During isothermal compression of air, the work-done in a compressor is maximum


  3. Which of the following statement is correct?

  4. A.

     The reciprocating compressors are best suited for high pressure and low volume capacity

    B.

     The effect of clearance volume on power consumption is negligible for the same volume of discharge

    C.

     Both (A) and (B)

    D.

     None of these


  5. The assumption made in two stage compression with inter-cooler is that

  6. A.

     There is no pressure drop in the inter-cooler

    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


  7. The temperature of air at the beginning of the compression stroke is ________ the atmospheric temperature.

  8. A.

     Equal to

    B.

     Less than

    C.

     More than

    D.

     None of these


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

  10. A.

     Forward curved

    B.

     Backward curved

    C.

     Radial

    D.

     None of these


  11. The volumetric efficiency of compressor with increase in compression ratio will

  12. A.

     Increase

    B.

     Decrease

    C.

     Remain same

    D.

     May increase or decrease depending on clearance volume


  13. The thermodynamic efficiency of rotary compressor is based on

  14. A.

     Isothermal compression

    B.

     Adiabatic compression

    C.

     Isentropic compression

    D.

     Polytropic compression


  15. The ratio of work-done per cycle to the stroke volume of the compressor is known as

  16. A.

     Compressor capacity

    B.

     Compression ratio

    C.

     Compressor efficiency

    D.

     Mean effective pressure


  17. The stagnation pressure rise in a centrifugal compressor takes place

  18. A.

     In the diffuser only

    B.

     In the impeller only

    C.

     In the diffuser and impeller

    D.

     In the inlet guide vanes only


  19. 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

  20. 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