Energy loss analysis of transition simulation for a prototype reversible pump turbine during load rejection process

Abstract

The dynamic behavior of a reversible pump turbine (RPT) during the load rejection process was investigated through numerical simulation and experimental testing. The study focused on various parameters, such as the operation of guide vanes, torque, flow, head, and runner forces. The pressure fluctuations at different monitoring points were analyzed using the time-frequency method, specifically the continuous wavelet transforms (CWT). The results revealed significant pressure pulsation amplitudes in the vaneless region. Additionally, the entropy production rate was employed to quantify energy loss in different domains, including direct dissipation, turbulent dissipation, and wall shear stress. Moreover, the study utilized the vorticity transport equation to examine vortex characteristics and transport in the stay vanes, guide vanes, and runner flow channels. The vortex characteristics were classified into relative vortex stretching (RVS), Coriolis force (CORF), and viscous diffusion (VISD). The findings highlight significant energy loss in flow patterns associated with high RVS and CORF regions. This study provides valuable insights into the transition process and energy loss of RPTs during load rejection, serving as a basis for future research aiming to enhance the safety and reliability of RPTs under load rejection conditions.