Performance comparison between forward curved blade impeller and backward curved blade impeller in mixed-flow pump-as-turbine

To explore the performance characteristics of a mixed-flow pump-as-turbine (MF-PAT) with forward curved blades, two types of impellers with the same diameter, with forward curved blades and backward curved blades, were designed. Through a combination of numerical simulation and experimental verification, the performance and internal flow characteristics of the two types of blades in the MF-PAT were compared. The results indicate that in the overload region, the performance of the forward curved blades is better. The flow rate at the efficient point of the forward curved blade is 1.5 times that of the backward curved blade, and the efficient range is 2.5 times that of it. In the overload region, the hydraulic loss of the forward curved blades accounts for only 40%, while the backward curved blades account for up to 70%. Forward curved blades can effectively reduce hydraulic losses and improve the internal flow of the impeller. The loss of backward curved blades is mainly concentrated on the blade working surface and blade inlet, while the loss of forward curved blades is mainly concentrated on the blade outlet. Compared to traditional backward curved blades, forward curved blade impellers have advantages such as a wider efficiency range and smaller volume. These findings provide valuable insights for optimizing the design and performance of MF-PATs.