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Fluid Mechanics
Bernoulli's Equation & Flow
GATE 2020
Hard

The values of enthalpies at the stator inlet and rotor outlet of a hydraulic turbomachine stage are h1 and h3 respectively. The enthalpy at the stator outlet (or, rotor inlet) is h2. The condition (h2−h1) = (h3−h2) indicates that the degree of reaction of this stage is

  • Azero
  • 50%
  • C75%
  • D100%

Explanation

Degree of reaction R = (h2−h3)/(h1−h3). The given condition h2−h1=h3−h2 rearranges to 2h2=h1+h3, i.e. h2 is exactly the average of h1 and h3. Then h2−h3=(h1−h3)/2, so R=(h2−h3)/(h1−h3)=1/2=50%.

Source: GATE ME 2020 Session 2 (ME-2) (2020)

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