# Power Plant Questions and Answers – Turbine and Nozzles Types

This set of Power Plant Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Turbine and Nozzles Types”.

1. What is the purpose of governing in steam turbines?
a) reheat the steam and improve its quality
b) maintain the speed of the turbine
c) reduce the effective heat drop
d) completely balance against end thrust

Explanation: The purpose of governing in steam turbines is to maintain the speed of the turbine.

2. The ratio of the work done on the blades per kg of steam to the total energy supplied per stage per kg of steam is called?
a) nozzle efficiency
b) stage efficiency
c) mechanical efficiency

Explanation: The ratio of the work done on the blades per kg of steam to the total energy supplied per stage per kg of steam is called Stage Efficiency.

3. A nozzle is said to be a divergent nozzle ____________
a) when the cross-section of the nozzle increases continuously from entrance to exit
b) when the cross-section of the nozzle decreases continuously from entrance to exit
c) when the cross-section of the nozzle first decreases from entrance to throat and then increases from its throat to exit
d) none of the mentioned

Explanation: A nozzle is said to be a divergent nozzle when the cross-section of the nozzle increases continuously from entrance to exit.

4. The ratio of the isentropic heat drop to the heat supplied is called ____________
a) stage efficiency
b) reheat factor
c) internal efficiency
d) rankine efficiency

Explanation: The ratio of the isentropic heat drop to the heat supplied is called Rankine efficiency.

5. The reheat factor depends upon ____________
a) exit pressure
b) turbine stage efficiency
c) initial pressure and superheat
d) all of the mentioned

Explanation: The factors on which the reheat factor depends are exit pressure, turbine stage efficiency, initial pressure & superheat.

6. What is the critical pressure ratio for initially dry saturated steam?
a) 0.546
b) 0.577
c) 0.586
d) 0.578

Explanation: The critical pressure ratio for initially dry saturated steam is 0.577.

7. In order to reduce the rotor speed of an impulse turbine, the method employed is ____________
a) pressure compounding
b) velocity compounding
c) pressure-velocity compounding
d) all of the mentioned

Explanation: In order to reduce the rotor speed of an impulse turbine, the methods employed are
Pressure compounding, Velocity compounding, Pressure-Velocity compounding, etc.

8. Which of the following statement is wrong?
a) The flowing the convergent portion of the nozzle is sub-sonic
b) The critical pressure gives the velocity of steam at the throat equal to the velocity of sound
c) The flow in the divergent portion of the nozzle is super-sonic
d) To increase the velocity of steam above sonic velocity (super-sonic) by expanding steam below the critical pressure, the divergent portion for the nozzle is not necessary

Explanation: In order to increase the velocity of steam above sonic velocity by expanding steam below the critical pressure, the divergent portion for the nozzle is necessary.

9. In an impulse turbine, steam expands ____________
a) wholly in nozzle
b) partly in the nozzle and partly in blades
d) none of the mentioned

Explanation: In an impulse turbine, steam expands wholly in nozzle.

10. A steam nozzle converts ____________
a) heat energy of steam into potential energy
b) potential energy into heat energy of steam
c) heat energy of steam into kinetic energy
d) kinetic energy into heat energy of steam

Explanation: A steam nozzle converts heat energy of steam into kinetic energy.

11. The process of draining steam from the turbine, at certain points during its expansion and using this steam for heating the feed water in feed water heaters and then supplying it to the boiler is known as?
a) regenerative heating
b) reheating of steam
c) bleeding
d) none of the mentioned

Explanation: The process of draining steam from the turbine, at certain points during its expansion and using this steam for heating the feed water in feed water heaters and then supplying it to the boiler is known as Bleeding.

12. If the critical pressure ratio for steam is 0.546, then the steam is initially ____________
a) wet
b) dry saturated
c) superheated
d) none of the mentioned

Explanation: Generally, when the critical pressure ratio for steam is 0.546, then the steam is said to be superheated.

13. A steam turbine, in which a part of the steam after partial expansion, is used for process heating and the remaining steam is further expanded for power generation, is known as?
a) pass out turbine
b) impulse turbine
c) low pressure turbine
d) high pressure turbine

Explanation: A steam turbine, in which a part of the steam after partial expansion, is used for process heating and the remaining steam is further expanded for power generation, is known as Pass out Turbine.

14. A stage, in reaction turbine, is represented by ____________
b) number of entries of steam
c) number of exits of steam
d) none of the mentioned

Explanation: Each row of blades represents each stage in a reaction turbine.

15. Which of the following statement is correct?
a) The pressure of steam, in reaction turbines, is increased in fixed blades as well as in moving blades
b) The efficiency of steam turbine is greater than the steam engines
c) A flywheel is a must for steam turbine
d) The turbine blades do not change the direction of steam issuing from the nozzle

Explanation: The efficiency of steam turbines is greater than that of a steam engine.

Sanfoundry Global Education & Learning Series – Power Plant Engineering.

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