Internal flow characteristics of water-ring of pump-turbine during pump mode’s starting-up

Abstract

Abstract Synchronous condenser mode is an important process for the conversion of pumped storage units. The compressed air is injected into the runner passage to reduce the input power under the condition of pump mode’s starting-up. In this study, a pump turbine model with medium specific speed was utilized for investigating the internal flow characteristic of water-ring. Unsteady state analysis was conducted with the turbulence model of RNG k-ε and multiphase flow model of VOF. The internal flow of the vaneless and the tandem cascade spaces was examined under the water-ring phenomenon. The results show that the air and water form an interface in the vaneless space obviously and a certain thickness of water-ring was formed. Water-ring prevents the air from runner passage into casing, which play a sealing role.