Mining Methods and Machinery · Mining Machinery · 2 marks · Numerical answer
A water turbine pump has backward-curved impellers of diameter 35 cm running at 1200 rpm. Blade angle is 30°, radial discharge speed 2 m/s and manometric efficiency 0.8. Find the number of impellers needed for 300 m lift, rounding upward.
Peripheral speed is u=π×0.35×1200/60=21.9911 m/s. For backward blades and no inlet whirl, outlet whirl is Vw=u−Vr cot30°=18.5270 m/s. Euler head per stage is uVw/g; delivered head is 0.8uVw/9.81≈33.23 m. Required stage count is 300/33.23≈9.03, which must be rounded upward to 10 impellers.
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