Research on Energy Loss Characteristics of Pump-Turbine during Abnormal Shutdown

Abstract

Pumped-storage hydropower (PSH) stations are an efficient emission-free technology to balance renewable energy generation instabilities. The pump-turbine is a core component of PSH stations requiring frequent start-up, shutdown, and working conditions for regulation tasks, making it prone to instabilities. Based on entropy production theory and vortex dynamics, we analyzed the energy loss characteristics for three working conditions of the pump, pump brake, and turbine when shutting down the pump-turbine. The results showed that the entropy production and vorticity of the spiral casing and draft tube remain almost constant, while the entropy production and vorticity of the runner region substantially change from the late pump braking to the late turbine condition. The entropy production and vorticity are derived from the guide vane transitioning to the runner flow channel through the vaneless space. The change law of energy loss through entropy production agrees with the change law of internal flow turbulence through vorticity. The entropy production analysis can quantify the energy loss and mark its location, while the vorticity analysis can quantify the degree of flow disturbance and show its location. The entropy production theory and vortex dynamics combination provide insights into the connection between undesirable flow phenomena and energy loss.