If Vâ‚ and Vâ‚‚ are the velocities of water at inlet and outlet of the draft tube respectively, then the efficiency of a draft tube is

Mechanical Engineering : Hydraulic Machines - Quiz(MCQ)

Vâ‚ / Vâ‚-Vâ‚‚

Vâ‚-Vâ‚‚ / Vâ‚

Vâ‚Â² / Vâ‚Â²-Vâ‚‚Â²

Vâ‚Â²-Vâ‚‚Â² / Vâ‚Â²

Correct Answer : Option (D) : Vâ‚Â²-Vâ‚‚Â² / Vâ‚Â²

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It is given that the input water power of the Kaplan turbine is 1.10 times the runner power. What would be the hydraulic efficiency of the turbine (in %)?

70.71

80.81

90.91

100.00

Correct Answer : 90.91

Explanation : The definition of Hydraulic efficiency in a Kaplan turbine states that it is the ratio between the Runner power to the shaft power. If input water power is 1.10 times the runner power, the runner power is 1/1.10 = 0.90909 Times the water power. Hence, hydraulic efficiency = 90.91%.

Which of the following efficiencies for Kaplan Turbine is described as the ratio between the power produced by runner to the power supplied by water at the inlet?

Overall efficiency

Volumetric efficiency

Mechanical efficiency

Hydraulic efficiency

Correct Answer : Hydraulic efficiency

Explanation : The definition of Hydraulic efficiency in a Kaplan turbine states that it is the ratio between the Runner power to the shaft power. Hence, the correct option is Hydraulic efficiency.

Which of the following turbines will have the lowest number of blades in it?

Kaplan turbine

Steam turbine

Pelton turbine

Francis turbine

Correct Answer : Kaplan turbine

Explanation : As the head for Kaplan turbine is low, the discharge of water through the turbine is high and hence, blade resistance should be low. That’s why Kaplan turbine will have the lowest number of blades.

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