Question

The specific speed (N_s) of a centrifugal pump is given by-

1. \(\frac{N\sqrt{Q}}{H^{\frac{1}{4}}}\)
2. \(\frac{N\sqrt{Q}}{H^{\frac{5}{4}}}\)
3. \(\frac{N\sqrt{Q}}{H^{\frac{2}{3}}}\)
4. \(\frac{N\sqrt{Q}}{H^{\frac{3}{4}}}\)

Answer 1

Correct Answer - Option 4 : \(\frac{N\sqrt{Q}}{H^{\frac{3}{4}}}\)

Concept:

• The specific speed of a centrifugal pump is defined as the speed of a geometrically similar pump which would deliver one cubic metre of liquid per second against a head of one metre.
• \({N_s} = \frac{{N\sqrt Q }}{{H_m^{3/4}}}\)

• The specific speed (Ns) of a turbine is defined as, the speed of a geometrically similar Turbine that would develop unit Power (P) when working under a unit Head (H) (1 m head).
• Specific speed for the turbine is given by:
• \({N_s} = \frac{{N\sqrt P }}{{{H^{\frac{5}{4}}}}}\)