Experimental and Numerical Investigation of a Bánki Turbine Operating far away from Design Point

This paper presents the results of a combined experimental and numerical study on a Bánki turbine with horizontal nozzle, operating at heads and discharges that go below 5% and 30%, respectively, of the rated values. The experimental results suggest that, even for such dramatic decreases in the values of the operating parameters, the turbine could still attain a peak efficiency of more than 55%, although at the expense of a significant decrease in speed. To get an insight into the flow through the turbine, numerical simulations were carried out. The results obtained are in good agreement with the experiments. They suggest that far away from design point the energy transfer inside the runner suffers a significant change when compared with the normal operation, most of the energy being now transferred on the second pass.