Experimental study of characteristic curves of centrifugal pumps working as turbines in different specific speeds

Pump manufacturers do not normally provide the characteristic curves of their pumps working as turbines. Therefore, establishing a correlation between the performances of direct (pump) and reverse (turbine) modes is essential in selecting the proper machine.In this paper, several centrifugal pumps (Ns < 60 (m, m3/s)) were tested as turbines. Using experimental data, some relations were derived to predict the best efficiency point of a pump working as a turbine, based on pump hydraulic characteristics. Validity of the presented method was shown using some referenced experimental data.Two equations were presented to estimate the complete characteristic curves of centrifugal pumps as turbines based on their best efficiency point. Deviation of suggested method from experimental data were considered and discussed. Finally, a procedure was presented for selecting a suitable pump to work as a turbine in a small hydro-site.