Steam at a velocity of 10 m/s enters the impulse turbine

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Steam at a velocity of 10 m/s enters the impulse turbine stage with symmetrical blading having blade angle 30°. The enthalpy drop in the stage is 100 kJ. The nozzle angle is 20°. The maximum blade efficiency (in percent) is ____.

1. 88.3 %
2. 87.3 %
3. 88.5 %
4. 87.5 %

Correct Option: A

85.1 to 89.9
Maximum blade efficiency
η _max = cos² α
= .883
= 88.3%