Effect of blade profile on the hydraulic performance of a double-suction centrifugal pump as turbine based on enstrophy dissipation theory

Pump as turbine (PAT) is widely used in micro hydropower stations and chemical industries as an economical energy recovery device. The special impeller with forward-curved blades can significantly improve the efficiency of PAT and expand its high-efficiency range due to the suitable blade profile, which is more appropriate for PAT's operation mode than the backward-curved blades. To study the influence of the forward blade on a double-suction centrifugal PAT performance, three forward-curved blade schemes with different blade angle conditions are compared with the original backward-curved blade scheme. The three forward-curved blade schemes have the highest efficiency when the inlet angles are 60°, 90°, and 120°, respectively, and the appropriate blade outlet angle. The results showed that the forward-curved blade is suitable for high-flow rate operating conditions in double-suction centrifugal PAT. The PAT with a forward-curved blade impeller has higher efficiency and a broader high-efficiency region than the backward-curved blade impeller. The double-suction centrifugal PAT's main energy loss comes from the impeller's turbulent loss. The forward-curved blade reduces the impeller's turbulence loss and improves the PAT's efficiency at large flow rates. The research in this paper provides a theoretical basis for the design and application of double-suction centrifugal PAT.