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

This set of Power Plant Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Turbine Efficiency and Flow Through Nozzles – I”.

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

Explanation: The steam leaves the nozzle at low pressure & a high velocity as the action of steam is best suited for turbine operations under these conditions.

2. When the back pressure of a nozzle is below the designed value of pressure at exit of nozzle, the nozzle is said to be ____________
a) overdamping
b) underdamping
c) chocked
d) none of the mentioned

Explanation: When the back pressure of a nozzle is below the designed value of pressure at exit of nozzle, the nozzle is said to be underdamping.

3. De-Laval turbine is a ____________
a) multi rotor impulse turbine
b) impulse reaction turbine
c) single rotor impulse turbine
d) none of the mentioned

Explanation: A De-Laval turbine is a single rotor impulse turbine.

4. The supersaturated flow of steam through a nozzle as compared to a stable flow, the available heat drop ____________
a) increases
b) decreases
c) is unpredictable
d) remains same

Explanation: The supersaturated flow of steam through a nozzle as compared to a stable flow, the available heat drop decreases.

5. A turbine is said to have an axial discharge when the steam leaves the blade tip at __________ to the direction of the blade motion.
a) 90°
b) 60°
c) 270°
d) 180°

Explanation: A turbine is said to have an axial discharge when the steam leaves the blade tip at 60°
to the direction of the blade motion.

6. The Parsons’ reaction turbine has ____________
c) fixed and moving blades of different shape
d) identical fixed and moving blades

Explanation: The Parsons’ reaction turbine has identical fixed & moving blades.

7. What is the critical pressure ratio for initially wet steam?
a) 0.582
b) 0.546
c) 0.577
d) 0.601

Explanation: The critical pressure ratio for initially wet steam is 0.582.

8. The ratio of the useful heat drop to the isentropic heat drop is called ____________
a) condenser efficiency
b) nozzle efficiency
c) vacuum efficiency
d) boiler efficiency

Explanation: The ratio of the useful heat drop to the isentropic heat drop is called nozzle efficiency.

9. Rateau turbine is ____________
a) pressure-velocity compounded turbine
b) simple reaction turbine
c) velocity compounded turbine
d) pressure compounded turbine

Explanation: A Rateau turbine is a pressure compounded turbine.

10. When the cross-section of a nozzle increases continuously from entrance to exit, it is called a ____________
a) convergent-divergent nozzle
b) divergent nozzle
c) convergent nozzle
d) none of the mentioned

Explanation: When the cross-section of a nozzle increases continuously from entrance to exit, it is called a divergent nozzle.

Sanfoundry Global Education & Learning Series – Power Plant Engineering.

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