Numerical simulation and experimental investigation on the influence of the clocking effect on the hydraulic performance of the centrifugal pump as turbine

With the increasing attention to small hydropower, research on improving the hydraulic performance of the pump as turbine (PAT) has become more important. Therefore, to study the influence of clocking effects on the hydraulic performance of PAT, numerical simulation and experimental verification of different guide vane clocking positions are carried out in this paper. The angle between the trailing edge of the guide vane and the volute tongue, θ, is set in eight schemes from 0 to 70 deg. The maximum difference in the efficiency of the eight schemes can reach 2.45% at 80 m3/h. When the flow rate is more than 48 m3/h, the scheme with θ of 50° shows the highest efficiency. The regression equations of entropy generation and total pressure loss are established to obtain visual energy loss. The results indicate that energy loss of the stationary components changes significantly under different schemes, which is the main reason for the change in the efficiency of PAT. Besides, the stator-rotor interaction makes the energy loss near the wake region of the impeller change periodically. This research not only reveals the cause of the clocking effect but also provides a new perspective for the optimization of PAT structures.