Analysis of the bucket surface cavitation characteristics of a model Pelton turbine

Abstract

Abstract The internal flow in the rotating bucket of high-head Pelton turbine is complex problem with features of multiphase flow and free surface. As the runner rotating, high speed water jets continuously impact the buckets, which would cause the cavitation on the bucket surface. As proved by field practice, cavitation and cavitation erosion surely exists in the Pelton turbine, which is harmful for the hydraulic performance and the unit. This paper investigated the unsteady 3D water-air-vapour multiphase cavitation flow on the bucket surface of a model Pelton turbine under a high operating head. Results showed cavitation occurred during the process of the bucket cut into the water jet on both sides of the bucket cutout edge. The cavitation on the bucket front surface last for about 20 transient steps with a maximum vapor volume fraction of about 3%, while severe cavitation occurred on the rear surface of the splitter with the duration twice of that on the front surface and a maximum vapour volume fraction of approximately 100%.