GATE 2026 MN – Question 56

Mining Methods and Machinery · Mining Machinery · 2 marks · Numerical answer

A turbine pump generates60 m water head at2000 rpm with manometric efficiency70%. Neglect impeller-blade curvature. Find impeller diameter in cm to two decimals.

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Correct answer: 26.00 to 29.00

Explanation

With the stated radial-outlet approximation, manometric head is ηu²/g. Thus rim speed u=√(60×9.81/0.70)≈29.00 m/s. Since u=πDN/60, D=60u/(π×2000)≈0.2769 m=27.69 cm. The efficiency reduces delivered head relative to the ideal velocity head.

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