# Hydraulic Machines Questions and Answers – Turbines – 2

This set of Hydraulic Machines Interview Questions and Answers focuses on “Turbines – 2”.

1. Maximum Number of jets, generally, employed in an impulse turbine without jet interference can be?
a) 2
b) 3
c) 4
d) 6

Explanation: Equating equations of initial jet velocity and energy of a turbine, we get the minimum number of jets to be 6.

2. The overall efficiency of a reaction turbine is the ratio of
a) Actual work available at the turbine to the energy imparted to the wheel
b) Work done on the wheel to the energy (or head of water) actually supplied to the turbine
c) Power produced by the turbine to the energy actually supplied by the turbine
d) Actual work available at the turbine to energy imparted to the wheel

Explanation: The overall efficiency of any turbine will be mechanical efficiency * hydraulic efficiency.

3. In a reaction turbine, the draft tube is used to _________
a) To increase the head of water by an amount that is equal to the height of the runner outlet above the tail race
b) To prevent air to enter the turbine
c) To increase pressure energy of water
d) To transport water to downstream

Explanation: A draft tube influences performance of a turbine. It is located below the runner to decelerate flow velocity.

4. In reaction turbine hydraulic efficiency is______________
a) Ratio of actual work at the turbine to the energy imparted to the wheel
b) Ratio of work done on the wheel to energy that is supplied to the turbine
c) Ratio of power produced by the turbine to the energy actually supplied by the turbine
d) Ratio of Work done on the wheel to the energy (or head of water) actually supplied to the turbine

Explanation: In turbines, overall efficiency is the product of hydraulic and mechanical efficiencies. Here the hydraulic efficiency is ratio of work done to head of water.

5. Consider an inward flow reaction turbine, here, water _______
a) Flows parallel to the axis of the wheel
b) Enters the wheel at the outer periphery and then flows towards the centre of the wheel
c) Flow is partly radial and partly axial
d) Enters at the centre of the wheel and then flows towards the outer periphery of the wheel

Explanation: In any inward reaction flow turbine, water enters the outer periphery towards the centre of the wheel.
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6. The working of which of the following hydraulic units is based on Pascal’s law?
a) Air lift pump
b) Hydraulic coupling
c) Hydraulic press
d) Jet pump

Explanation: Pascal’s law can be described as the rate of flow of volume is constant. Hydraulic press uses similar principle.

7. Which kind of turbine is a Pelton Wheel turbine?
a) Tangential flow turbine
c) Outward flow turbine
d) Inward flow turbine

Explanation: Tangential turbine is one which water strikes runner in direction of the tangent to wheel of the turbine.

8. IN what type of turbine water enters in radial direction and leaves axial direction?
a) Tangential flow turbine
b) Axial flow turbine
c) Outward flow turbine
d) Mixed flow turbine

Explanation: Only in a mixed flow turbine, water enters in radial direction and leaves axial direction.

9. How many types of turbines can you classify on the basis of direction of flow through runner?
a) 6
b) 3
c) 4
d) 7

Explanation: There are 4 types of turbines, namely tangential, radial, axial, mixed flow turbines.

10. Into how many types can you classify radial flow turbines?
a) 4
b) 3
c) 6
d) 2

Explanation: We can classify radial flow turbines into 2 types, namely inward radial flow and outward radial flow.

11. Into how many types can you classify turbines on basis of head at inlet?
a) 3
b) 4
c) 6
d) 5

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