Comparative Numerical Studies for the Flow Energy Dissipation Features in a Vertical Two‐Stage Centrifugal Pump in Pump and Turbine Conditions

The vertical two‐stage centrifugal pump (VTSP) is well‐suited for small pumped storage power stations with high head and low discharge, such as those found in underground mines. Based on entropy theory, this study presents a comparative numerical analysis of the flow energy dissipation (FED) in a VTSP under two distinct operating conditions: pump condition and turbine condition, both characterized by relatively high hydraulic efficiencies of 88.9% and 87.4%, respectively. The numerical solutions were obtained using the steady‐state single‐phase SST k‐ω turbulence model. The results indicate that the region within 2 mm of the wall contributes the majority of the FED production in both pump and turbine conditions. This portion of the FED is influenced by the viscosity‐dominated flow‐wall interaction. In pump condition, the highest FED production occurs in the return channel, with the backward vane and forward vane regions contributing 38.3% and 14.4%, respectively. In turbine condition, the highest FED production occurs in the runners, with the first and second‐stage runners contributing 43.7% and 21.4%, respectively. To enhance efficiency in both modes, reducing the surface roughness of the flow channels is recommended. Additionally, optimizing the alignment between the guide vanes within the return channel and the fluid, as well as improving the matching between the runner blades and the fluid, can further improve efficiency in pump and turbine conditions, respectively.