# Hydraulic Machines Questions and Answers – Pelton Turbine Velocity Diagrams

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This set of Hydraulic Machines Multiple Choice Questions & Answers (MCQs) focuses on “Pelton Turbine Velocity Diagrams”.

1. Velocity triangles are used to analyze ____________
a) Flow of water along blades of turbine
b) Measure discharge of flow
c) Angle of deflection of jet
d) Flow of water, measure of discharge, angle of deflection

Explanation: By using velocity triangles we can determine discharge of flow, angle of deflection of jet and to measure relative velocity of jet with respect to speed of wheel.

2. In which of following turbine inlet and outlet blade velocities of vanes are equal?
a) Francis turbine
b) Kaplan turbine
c) Pelton turbine
d) Propeller turbine

Explanation: In Pelton turbine each blade has same angular velocity and same linear speed unlike Francis and Kaplan turbines.

3. Tangential velocity of blade of Pelton wheel is proportional to ____________
a) Speed of wheel
b) Angular velocity of wheel
c) Rpm of wheel
d) Speed, angular velocity, RPM of the wheel

Explanation: Usually velocity of blade is given by u=radius*angular velocity from which velocity is proportional to speed of wheel.

4. The value of coefficient of velocity is _____________
a) 0.98
b) 0.65
c) 0.85
d) 0.33

Explanation: Coefficient of velocity is defined as ratio of actual velocity of jet at vena contraction to theoretical velocity. Its value is approximate to 0.98.

5. In which of following turbine inlet whirl velocity and inlet jet velocity are equal in magnitude?
a) Pelton turbine
b) Propeller turbine
c) Kaplan turbine
d) Francis turbine

Explanation: In Pelton turbine velocity of inlet is parallel to splitter and is parallel to x axis which doesn’t have flow velocity.

6. In Pelton wheel, if outlet velocity angle of jet is “acute angled” then outlet whirl velocity of jet is ______________
a) x- component of V(r2) – blade velocity
b) x- component of V (r2) + blade velocity
c) Blade velocity – x- component of V (r2)
d) Zero

Explanation: By constructing velocity triangle we come to know that whirl velocity of jet is equal in magnitude to that of x- component of V r2 – blade velocity.

7. In Pelton wheel, if outlet velocity angle of jet is “obtuseangled” then outlet whirl velocity of jet is _____________
a) x- component of V (r2) – blade velocity
b) x- component of V (r2) + blade velocity
c) Blade velocity – x- component of V (r2)
d) Zero

Explanation:By constructing velocity triangle we come to know that whirl velocity of jet is equal in magnitude to that of Blade velocity – x- component of V (r2).

8. In Pelton wheel, if outlet velocity angle of jet is “right angled” then outlet whirl velocity of jet is __________
a) x- component of V (r2) – blade velocity
b) x- component of V (r2) + blade velocity
c) Blade velocity – x- component of V (r2)
d) Zero

Explanation: By constructing velocity triangle we come to know that whirl velocity of jet is equal to zero as x- component of V(r2)= blade velocity.

9. In Pelton wheel, relative inlet velocity of jet with respect to velocity of vane is _____________
a) Difference between inlet jet velocity and blade velocity
b) Sum of inlet jet velocity and blade velocity
c) Inlet jet velocity

Explanation: In Pelton turbine, inlet velocity of jet and velocity of vanes are in same direction and of different magnitude hence relative velocity is found by calculating its difference.

10. In Pelton wheel if angle of deflection is not mentioned then we assume it as______________
a) 150 degrees
b) 200 degrees
c) 165 degrees
d) 185 degrees

Explanation: It is standard value for deflection of jet, which is found by performing several experimental operations.

Sanfoundry Global Education & Learning Series – Hydraulic Machines.

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