# Power Plant Questions and Answers – Turbine Efficiency and Flow Through Nozzles – II

This set of Power Plant Questions and Answers for Campus interviews focuses on “Turbine Efficiency and Flow Through Nozzles – II”.

1. The value of the reheat factor varies from ____________
a) 1.08 to 1.10
b) 1.2 to 1.6
c) 1.6 to 2
d) 1.02 to 1.06

Explanation: The value of the reheat factor varies from 1.02 to 1.06.

2. The difference in supersaturated temperature and saturation temperature at that pressure is called ____________
a) degree of super saturation
b) degree of superheat
c) degree of undercooling
d) none of the mentioned

Explanation: The difference of supersaturated temperature and saturation temperature at that pressure is called degree of undercooling.

3. Parson’s turbine is a ____________
a) simple impulse turbine
b) impulse-reaction turbine
c) simple reaction turbine
d) none of the mentioned

Explanation: Parson’s turbine is a simple reaction turbine.

4. In reaction turbines, the axial thrust is due to ____________
a) pressure drop across the rotor
b) change in axial velocity
c) both pressure drop across the rotor and change in axial velocity
d) none of the mentioned

Explanation: In reaction turbines, the axial thrust is due to the pressure drop across the rotor & change in axial velocity.

5. The flow of steam is super-sonic ____________
a) in the convergent portion of the nozzle
b) at the entrance to the nozzle
c) at the throat of the nozzle
d) in the divergent portion of the nozzle

Explanation: The flow of steam is super-sonic in the divergent portion of the nozzle.
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6. The variation of steam pressure in the nozzle depends upon ____________
a) dryness fraction of steam
b) specific volume of steam
c) velocity of steam
d) all of the mentioned

Explanation: The variation of steam pressure in the nozzle depends upon dryness fraction of steam, specifically volume of steam & velocity of steam.

7. A binary vapour plant consists of ____________
a) mercury boiler
b) steam turbine
c) steam condenser
d) all of the mentioned

Explanation: A binary vapour plant consists of mercury boiler, steam turbine, steam condenser, etc.

8. The steam enters the nozzle at a ____________
a) low pressure and a low velocity
b) high pressure and a low velocity
c) low pressure and a high velocity
d) high pressure and a high velocity

Explanation: The steam enters the nozzle at a high pressure & a high velocity to force the maximum volume into the nozzle.

9. In a reaction turbine, when steam flows through the fixed blades ____________
a) pressure decreases while velocity increases
b) pressure increases while velocity decreases
c) pressure and velocity both increases
d) pressure and velocity both decreases

Explanation: In a reaction turbine, when steam flows through the fixed blades, the pressure decreases while velocity increases.

10. The impulse turbine rotor efficiency will have a maximum value of 0.5 cos2 α, where α is the nozzle exit flow angle, if the ____________
b) blade velocity coefficient is unity
d) blades are equiangular and frictionless

Explanation: The impulse turbine rotor efficiency will have a maximum value of 0.5 cos2 α, where α is the nozzle exit flow angle, if the blades are equiangular & frictionless.

11. Steam turbines are used for ____________
a) electric power generation
b) large marine propulsion
c) direct drive of fans, compressors, pumps
d) all of the mentioned

Explanation: Steam turbines are used for various applications which include, electric power generation, large marine propulsion, direct drive of fans, compressors, pumps, etc.

12. Curtis turbine is a ____________
a) pressure compounded turbine
b) velocity compounded turbine
c) simple reaction turbine
d) pressure-velocity compounded turbine

Explanation: A type of the pressure-velocity compounded turbine is a Curtis Turbine.

13. Which of the following statement is correct?
a) The expansion of steam in a nozzle follows Rankine cycle
b) The friction in the nozzle increases the dryness fraction of steam
c) The pressure of steam at throat is called critical pressure
d) All of the mentioned

Explanation: All the mentioned statements are correct.

14. Parson’s reaction turbine is a __________ reaction turbine.
a) 40%
b) 50%
c) 60%
d) 70%

Explanation: Parson’s reaction turbine is a 50% reaction turbine.

15. The diagram efficiency is the ratio of ____________
a) work done on the blades to the energy supplied to the blades
b) energy supplied to the blades per kg of steam to the total energy supplied per stage per kg of steam
c) work done on the blades per kg of steam to the total energy supplied per stage per kg of steam
d) none of the mentioned

Explanation: The diagram efficiency is the ratio of work done on the blades to the energy supplied to the blades.

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