Influence of cavitation simulation on Pelton turbine bucket performance

Abstract Cavitation is one of the crucial problems faced by Pelton turbines operating under high water heads. To evaluate the influence of cavitation on the predicted Pelton turbine bucket performance, the conventional water-gas two-phase flow simulation and the water-vapor-gas two-phase three component flow simulation were carried out at the design operating point of a six-nozzle model Pelton turbine. The results showed that the inclusion of cavitation model might induce obvious influence on the bucket front surface torque curve after the peak, which was originated from the cavitation simulated at bucket back surface during the cut-in process of the next bucket, deteriorating the jet flow pattern with secondary flow enhanced. The inflow of deformed jet piece onto the bucket front surface finally affected the hydraulic performance of the bucket, accounting for the runner hydraulic loss of about 0.5% after the inclusion of cavitation model. This study provided the idea that for the types of buckets vulnerable with cavitation, cavitation phenomenon should be included in the simulation, so as to obtain the performance predicted closer to reality.