Steam Nozzles and Turbines – Section 1

1. A nozzle is said to be a convergent 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 above

Correct Answer: B. when the cross-section of the nozzle decreases continuously from entrance to exit

2. 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. 60°
B. 90°
C. 180°
D. 270°

Correct Answer: B. 90°

3. The flow through a nozzle is regarded as

A. constant volume flow
B. constant pressure flow
C. isothermal flow
D. isentropic flow

Correct Answer: D. isentropic flow

4. The ratio of total useful heat drop to the total isentropic heat drop is called

A. stage efficiency
B. internal efficiency
C. Rankine efficiency
D. none of these

Correct Answer: B. internal efficiency

5. The pressure at which the steam leaves the nozzle is known as back pressure.

A. Correct
B. Incorrect

Correct Answer: A. Correct

6. The discharge of steam in a convergent-divergent nozzle __________ after the throat (i.e. in the divergent portion of the nozzle)

A. remains constant
B. decreases
C. increases

Correct Answer: A. remains constant

7. The rate of discharge through the nozzle __________ when the exit pressure is gradually reduced.

A. remains same
B. decreases
C. increases

Correct Answer: C. increases

8. The velocity of steam leaving the nozzle (V) is given by (where K = Nozzle coefficient or nozzle efficiency, and hd = Enthalpy or heat drop during expansion of steam in a nozzle)

sn-se1-08

Correct Answer: Option C

9. In a nozzle, whole frictional loss is assumed to occur between

A. inlet and throat
B. inlet and outlet
C. throat and exit
D. all of these

Correct Answer: C. throat and exit

10. The critical pressure ratio for initially wet steam is

A. 0.546
B. 0.577
C. 0.582
D. 0.601

Correct Answer: C. 0.582

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