The degree of reaction $R$ for an axial gas turbine stage is defined as $R = \frac{\Delta h_{rotor}}{\Delta h_{stage}}$. For an impulse turbine stage, the degree of reaction is:

(A) R = 0

(B) R = 0.5

(C) R = 1.0

(D) R = 0.75

Answer Key:

A

### Solution: In a pure impulse turbine stage, all static pressure drop and static enthalpy decrease occur across the stationary nozzle guide vanes (stator), while static pressure across the rotor remains constant ($R = 0$). Correct: A.

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