This set of Hydraulic Machines Multiple Choice Questions & Answers (MCQs) focuses on “Efficiencies of a Turbine”.

1. _____________ is defined as ratio between power delivered to runner and power supplied at inlet of turbine.

a) Mechanical efficiency

b) Volumetric efficiency

c) Hydraulic efficiency

d) Overall efficiency

View Answer

Explanation: Hydraulic efficiency is defined as ratio between power given by water to runner of turbine and to the power supplied by water at inlet of the turbine.

2. Which among the following which is not an efficiency of turbine?

a) Mechanical efficiency

b) Volumetric efficiency

c) Hydraulic efficiency

d) Electrical efficiency

View Answer

Explanation: Electrical efficiency is ratio of work output and electrical power input to electrical machine but turbine is a hydraulic machine which consists of only mechanical, volumetric and hydraulic efficiencies.

3. The ratio of power at the shaft of turbine and power delivered by water to runner is known as?

a) Mechanical efficiency

b) Volumetric efficiency

c) Hydraulic efficiency

d) Overall efficiency

View Answer

Explanation: Due to mechanical losses, power available at shaft of turbine is less than power delivered to the runner of turbine. Hence ratio of power at the shaft of turbine and power delivered by water to runner is known as mechanical efficiency.

4. The product of mechanical efficiency and hydraulic efficiency is known as?

a) Mechanical efficiency

b) Volumetric efficiency

c) Hydraulic efficiency

d) Overall efficiency

View Answer

Explanation: Overall efficiency is defined as ratio of power available at shaft of turbine to power supplied at the inlet of turbine which is also product of mechanical and hydraulic efficiency.

5. Among the following which turbine has highest efficiency?

a) Kaplan turbine

b) Francis turbine

c) Pelton turbine

d) Propeller turbine

View Answer

Explanation: Kaplan is inward flow reaction turbine and is operated under head less than 60 meters. The vanes attached to hub are adjustable and Kaplan is mainly operated in location where large quantity of water at low head is available.

6. _____________ is ratio of volume of water actually striking the runner and volume of water supplied to turbine.

a) Mechanical efficiency

b) Volumetric efficiency

c) Hydraulic efficiency

d) Overall efficiency

View Answer

Explanation: Volumetric efficiency is ratio between volume of water actually striking the runner of turbine and volume of water supplied to the turbine.

7. In the expression for overall efficiency of turbine, which is p/(k*g*q*h), where “k” is known as ___________

a) Density of liquid

b) Specific density of liquid

c) Volume of liquid

d) Specific gravity of liquid

View Answer

Explanation: Overall efficiency is defined as ratio of power available at shaft of turbine to power supplied at the inlet of turbine which is also product of mechanical and hydraulic efficiency. Its expression is given by p/(k*g*q*h) where k is density of liquid.

8. The expression for maximum hydraulic efficiency of pelton turbine is given by?

a) (1+cos k)/2 where k is outlet blade angle

b) (2+cos k)/2 where k is outlet blade angle

c) (3+cos k)/2 where k is outlet blade angle

d) (4+cos k)/2 where k is outlet blade angle

View Answer

Explanation: Hydraulic efficiency is defined as ratio between power given by water to runner of turbine and to the power supplied by water at inlet of the turbine. Its maximum value is obtained by replacing u=v/2 and it is (1+cos k)/2 where k is outlet blade angle.

9. To obtain maximum hydraulic efficiency of pelton turbine, blade velocity should be ___________ Times the inlet velocity of jet.

a) Half

b) One quarter

c) Twice

d) Thrice

View Answer

Explanation: Hydraulic efficiency is defined as ratio between power given by water to runner of turbine and to the power supplied by water at inlet of the turbine. This efficiency will be maximum when differentiating it with “u” and it is obtained as u=v/2.

10. Among the following which turbine has least efficiency?

a) Pelton turbine

b) Kaplan turbine

c) Francis turbine

d) Propeller turbine

View Answer

Explanation: Pelton turbine is an impulse turbine, where there is no theoretical limit for head due to high head there is loss due to friction when water passing through penstocks hence its efficiency is less.

11. The ratio of volume available at shaft of turbine and power supplied at the inlet of the turbine

a) Mechanical efficiency

b) Volumetric efficiency

c) Hydraulic efficiency

d) Overall efficiency

View Answer

Explanation: Overall efficiency is defined as ratio of power available at shaft of turbine to power supplied at the inlet of turbine which is also product of mechanical and hydraulic efficiency.

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