SSC JE Mechanical Engineering 11 Oct 2020 Shift 1 Papers

Question : 133 of 200

Marks: +1, -0

A Francis turbine has an overall efficiency of 83%. If it develops the power of 500 kW under a net head of 3000 cm, the discharge through the turbine in m

^{3}

/s is:

2.50
20.50
25.0
2.05

Validate

Solution:

Density of water

(\ρ)=1000 {kg} \/ {m}^{3}

Net head

({h})=3000 {cm}=30 {m}

Output power

{P}_{0}=500 {kW}

\η=83 \%=0.83

Acceleration due to gravity

(g)=9.8 {m} \/ {s}^{2}

Discharge

(Q)=?

Input power

({P}_{{i}})=\ρ {g} {Q} {h}

=1000 \×9.8 \×{Q} \×30=294 {Q} \×10^{3}

Efficiency,

\η ={P_{0}}/{P_{i}}

0.83={500 \×10^{3}}/{294 Q \×10^{3}}

discharge,

Q=2.05 {m}^{3} \/ {s}

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