Steam Nozzles and Turbines – Section 1

31. The critical pressure ratio (p2/p1) is given by

sn-se1-31

Correct Answer: Option B

32. In reaction turbines, the axial thrust is due to

A. pressure drop across the rotor
B. change in axial velocity
C. both (a) and (b)
D. none of these

Correct Answer: C. both (a) and (b)

33. 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 above

Correct Answer: D. all of the above

34. A binary vapor plant consists of

A. steam turbine
B. steam condenser
C. mercury boiler
D. all of these

Correct Answer: D. all of these

35. In a De-Laval nozzle expanding superheated steam from 10 bar to 0.1 bar, the pressure at the minimum cross-section (i. e. pressure at throat, p2) will be

A.3.3 bar
B.5.46 bar
C.8.2 bar
D.9.9 bar

Correct Answer: B. 5.46 bar

36. The stage efficiency (ηS) is given by (where ηB = Blading efficiency and ηN = Nozzle efficiency)

A. ηS = ηB x ηN
B. ηS = ηBN
C. ηS = ηNB
D. none of these

Correct Answer: A. ηS = ηB x ηN

37. The critical pressure ratio for initially dry saturated steam is more as compared to initially wet steam.

A. Yes
B. No

Correct Answer: B. No

38. In a convergent-divergent nozzle, the discharge depends upon the initial conditions of steam and the area of nozzle at throat.

A. Correct
B. Incorrect

Correct Answer: A. Correct

39. Parson’s reaction turbine is a __________ reaction turbine.

A. 40 percent
B. 50 percent
C. 60 percent
D. 70 percent

Correct Answer: B. 50 percent

40. The turbine blades are

A. straight
B. circular
C. curved

Correct Answer: C. curved

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