GATE Mechanical Engineering (ME) 2020 Shift 2 Solved Paper

Question : 13 of 65

Marks: +1, -0

The values of enthalpies at the stator inlet and rotor outlet of a hydraulic turbo machine stage are

h_{1}

and

h_{3}

respectively. The enthalpy at the stator outlet (or, rotor inlet) is

h_{2}

. The condition

(h_{2}-h_{1})=(h_{3}-h_{2})

indicates that the degree of reaction of this stage is

Solution:

Degree of reaction

(R)=\;{\;\text " Enthalpy drop in rotor "\;}/{\;\text " Total enthalpy drop "\;}

{R}=\;{ {h}_{3}- {h}_{2}}/{( {h}_{3}- {h}_{2})+( {h}_{2}- {h}_{1})}

Given

{h}_{2}- {h}_{1}= {h}_{3}- {h}_{2}

Thus

R=\;{(h_{3}-h_{2})}/{2(h_{3}-h_{2})}

R \;\; =0.50

R=50 \%

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