The influence of the middle bending shape of the blade on the performance of a pump as turbine.

As a kind of energy-saving and micro-hydropower utilization device, pump as turbine (PAT) is simple to construct with low operation and maintenance costs, which is widely used in the energy-consuming industrial processes and micro-hydro power generation. The variation law of blade angle from blade inlet to outlet has the characteristics of uncertainty and diversity, which determines the middle bending shape of the blade and has a direct impact on the fluid. Different blade bending shapes form different wrap angles on the premise of impeller outlet and inlet angles kept invariable. To investigate how the blade angle distribution affects the performance, four different impellers were created and analyzed based on computational fluid dynamics method. This paper investigates the effect of blade bending shapes on the performance characteristics, unsteady characteristics and energy loss of PAT. The numerical result shows due to the small blade wrap angle, the best efficiency of scheme 2 is the lowest among the four schemes, while the best efficiency of scheme 4 is the highest. The appropriate blade bending shape is beneficial to reduce the enstrophy dissipation and improve the efficiency and operating stability of PAT. These findings provide reference points for optimizing the blade profile in PAT. • Different angle distribution profiles from the blade inlet to the blade outlet will form different blade camber shapes. • Four PAT's impellers with different blade bending shapes are designed and investigated by a verified CFD method. • The appropriate blade bending shape can improve the operation stability and the unsteady flow characteristics of PAT. • It is beneficial to improve the PAT's performance that the blade camber shape is mainly concentrated in the blade middle. [ABSTRACT FROM AUTHOR]