Evolution and influence of pump-turbine cavitation during load rejection transients of a pumped-storage plant

Abstract

Load rejection is one of the most dangerous transients in pumped-storage plants, during which cavitation in pump-turbines is normally inevitable. In this study, we applied the one-dimensional and three-dimensional coupled computational fluid dynamics method to simulate the 100% load rejection transient process of a middle-head plant, analysed the evolution and influence of cavitation cavities, and evaluated the safety. During the guide-vane closing process, a spiral-shaped cavitation cavity under the runner cone and nine wedge-shaped cavitation cavities inside the blade channel outlets occur successively. Although no water column separation happens in the draft tube inlet, the collapses of the wedge-shaped cavities induce obvious impacts on the runner, causing axial force fluctuations, to which attention should be paid in the plant design phase. This study further validated the feasibility of the coupled method and revealed the mechanism of the dynamic cavitation phenomenon, which provides references for research and engineering design.