Analysis of flow energy dissipation of a two-stage storage pump based on entropy generation theory

A hybrid power station comprising storage pump units and conventional hydropower components holds the potential to enhance the operational flexibility of basin hydroelectric regulation. The storage pumps must possess significant power capacity and operate with high efficiency to ensure viable energy storage. This study investigates the energy dissipation within a two-stage storage pump using entropy generation theory. The numerical solution of flow energy dissipation (FED) components was obtained for various flow rates using the steady-state single-phase shear stress transport k–ω turbulence model. Results indicate that the return channel contributes the most to FED generation within the entire passage, with the FED proportion decreasing from 66.7% to 41.3% as the flow rate increases from 0.5Q_BEP to 1.2Q_BEP. The FED generation percentage from the runners increases from 10.4% to 46.9% with increasing flow rate, ranking second. The FED generation percentage attributed from the spiral case ranges from 10.3% to 16.7%, ranking third. Losses from the draft tube are found to be negligible. Flow pattern analysis reveals that FED generation primarily occurs at the junction of inferior flow (flow separation and vortex flow) and the main flow, where significant velocity gradients exist.