Mechanical Engineering - Steam Nozzles and Turbines

Exercise :: Steam Nozzles and Turbines - Section 3

36. 

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)

A. Vb = 0.5 V cos α
B. Vb = V cos α
C. Vb = 0.5 V2 cos α
D. Vb = V2 cosα

Answer: Option A

Explanation:

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37. 

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

A. minimum
B. maximum
C. zero

Answer: Option C

Explanation:

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38. 

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.

A. equal to
B. less than
C. greater than

Answer: Option A

Explanation:

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39. 

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

A. 10 to 15 percent
B. 15 to 25 percent
C. 25 to 40 percent
D. 40 to 60 percent

Answer: Option A

Explanation:

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40. 

An impulse turbine as compared to a reaction turbine, for a given power has __________ row of blades.

A. equal
B. less
C. more

Answer: Option C

Explanation:

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