Consider the following statements in connection with hydraulic turbines: 1. The Kaplan turbine is a radial flow turbine in which the guide vane angles as well as the runner vane angles are adjustable. 2. Francis and Kaplan turbines are provided with draft tubes which carry water from exit of runner to tail water to increase the gross head across the turbine. 3. The parts of turbines susceptible to cavitation are the guide vanes and runner vanes – drastically reducing the turbine efficiency. 4. The specific speed of a 4-jet Pelton turbine will be 28 if the specific speed of a single-jet Pelton turbine is 14. Which of the above statements are correct?

2 and 3 only
1 and 3 only
1 and 4 only
2 and 4 only

LohaHridoy

4 views

2025-01-04 04:42

1 Answers

AhmedNazir

Option 4 : 2 and 4 only

Concept:

The Kaplan turbine is an axial flow turbine in which the guide vane angles as well as the runner vane angles are adjustable.

If water flows along the tangent of runner, the turbine is known as Tangential flow turbine. Pelton turbine is the tangential flow turbine. If the water flows in radial direction through the runner, the turbine is known as Radial flow turbine. Francis turbine is radial flow turbine.

If water flows along the direction parallel to the axis of rotation of runner, the turbine is known as axial flow turbine. Kaplan and propeller turbine are the examples of axial flow turbine. If water flows in radial direction but leaves in the direction parallel to the axis of rotation, the turbine is known as mixed flow turbine. Modern Francis turbine is mixed flow turbine.

Francis and Kaplan turbines are provided with draft tubes which carry water from exit of runner to tail water to increase the gross head across the turbine. Draft tube generates negative head at the exit of the runner which helps in increasing the gross head across the turbine.

Cavitation may be defined as the phenomenon which manifests itself in the pitting of the metallic surfaces of turbine parts because of formation of cavities. So statement 3 is incorrect.

Specific speed of a turbine is directly proportional to the square root of the power. In a 4-jet Pelton turbine the power is 4 times of the power of a single jet Pelton turbine.

So the specific speed of a 4-jet Pelton turbine will be 28 if the specific speed of a single-jet Pelton turbine is 14.

So statement 2 & 4 are correct.

4 views Answered 2022-09-04 04:29

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