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Degree of reaction from enthalpy drops in a turbine stage Given: Isentropic enthalpy drop in the moving blade (rotor) is two-thirds of the isentropic enthalpy drop in the fixed blade (stator). Compute the degree of reaction R = (rotor drop)/(stator drop + rotor drop). Choose the correct value.

Difficulty: Medium

0.40
0.56
0.67
1.67

Correct Answer: 0.40

Explanation:

Given data

Let Δh_f = isentropic drop in fixed blades (stator).
Δh_m (moving/rotor) = (2/3) Δh_f.

Step-by-Step calculation
Total stage drop = Δh_f + Δh_m = Δh_f + (2/3)Δh_f = (5/3)Δh_f.R = Δh_m / (Δh_f + Δh_m) = ( (2/3)Δh_f ) / ( (5/3)Δh_f ) = 2/5 = 0.40.

Final Answer
0.40

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