Discussion :: Steam Nozzles and Turbines  Section 1 (Q.No.13)
13. 
The efficiency of reaction turbine is maximum when (where α = Angle made by the absolute velocity (V) at inlet) 
[A]. 
V_{b} = 0.5 V cos α  [B]. 
V_{b} = V cos α  [C]. 
V_{b} = 0.5 V^{2} cos α  [D]. 
V_{b} = V^{2} cos α 
Answer: Option B
Explanation:
No answer description available for this question.

Saikumar said:
(Mar 12, 2015)


Velocity ratio for impulse turbine = 0.5 cosθ.
Velocity ratio for reaction turbine = cosθ. 
Yashfa said:
(Jul 23, 2016)


How is this possible? 
Pal said:
(Aug 19, 2016)


The answer should be the option (a). 
N Suresh said:
(Dec 6, 2016)


When the efficiency of reaction turbine is maximum where blade velocity should be half. So that Vb = 0.5 V cos a. 
Vijay said:
(Dec 22, 2016)


Maximum efficiency is option B because (Vb/v)= cos. 
Biplab said:
(Dec 31, 2016)


For reaction turbine, max efficiency condition is cos alpha and in case of impulse turbine (cos alpha)/2. 
K910 said:
(Feb 7, 2020)


The answer is correct for rxn it is U/V=cos alpha for impulse it is cos(alpa)/2. 