Energy loss analysis of a multi-stage centrifugal pump using in pump mode and turbine mode

To enhance the application of multi-stage pump as turbine (PAT) for high-pressure energy recovery, a deeper understanding of their performance is essential. This study provides a comparative analysis of the energy loss mechanisms in a multi-stage centrifugal pump operating in both turbine and pump modes. Based on entropy generation theory, the analysis utilizes numerical simulations validated by experimental data. The results demonstrate that in both modes, turbulent entropy generation and wall entropy generation account for over 54 % and 37 % of the total entropy generation, respectively, while viscous entropy generation is less than 1 %. This indicates that the energy loss is primarily attributed to the unsteady flow in the mainstream region and the wall effects in the near-wall region. For both modes, the components with the high energy loss are the impeller, guide vane, and pump cavity. Furthermore, a significant difference in the dominant energy loss mechanisms between the two modes is revealed. In turbine mode, the primary loss stems from the mismatch between the flow angle and the blade angle at the impeller inlet. In contrast, for the pump mode, the dominant losses are caused by flow separation and the jet-wake structure within the flow channels. The front pump cavity is another major contributor to energy loss in both modes, where the resulting leakage generates internal vortices and backflow. This study not only provides insights into the energy loss characteristics of multi-stage centrifugal pumps in both modes but also offers new perspectives for their structural optimization.