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Mechanical Engineering :: Steam Nozzles and Turbines

  1. The efficiency of an impulse turbine is maximum when (where Vb = Blade speed, V = Absolute velocity of steam entering the blade, and α = Nozzle angle)

  2. A.

    Vb = 0.5 V cos α

    B.

    Vb = V cos α

    C.

    Vb = 0.5 V2 cos α

    D.

    Vb = V2 cosα

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  3. The velocity of whirl at outlet for an axial discharge turbine is

  4. A.

    minimum

    B.

    maximum

    C.

    zero

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  5. In impulse turbines, when friction is neglected, the relative velocity of steam at outlet tip of the blade is __________ the relative velocity of steam at inlet tip of the blade.

  6. A.

    equal to

    B.

    less than

    C.

    greater than

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  7. The friction present between the steam and the nozzle surfaces reduces the heat drop by

  8. A.

    10 to 15 percent

    B.

    15 to 25 percent

    C.

    25 to 40 percent

    D.

    40 to 60 percent

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  9. Degree of reaction is defined as the ratio of

  10. A.

    heat drop in fixed blades to the heat drop in moving blades

    B.

    heat drop in moving blades to the heat drop in fixed blades

    C.

    heat drop in moving blades to the heat drop in fixed blades plus heat drop in moving blades

    D.

    heat drop in fixed blades plus heat drop in moving blades to the heat drop in moving blades

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