Numerical investigations on performance improvement mechanism of a high-power vertical centrifugal pump with special emphasis on hydraulic component matching

The purpose of this paper is to investigate the performance improvement mechanism of a high power vertical centrifugal pump by using numerical calculations. Therefore, a comparative study of energy losses and internal flow characteristics in the original and optimized models was carried out with special attention to the hydraulic component matching. The optimized model (model B) was obtained by optimizing the vaned diffuser and volute based on the original model (model A), mainly the diffuser inlet diameter, diffuser inlet vane angle, volute channel inlet width and volute throat area were changed. Firstly, the comparative results on performance and energy losses of two models showed that the efficiency and head of model B was significantly increased under design and part-load conditions. It is mainly due to the dramatic reduction of energy loss P_L in the diffuser and volute. Then, the comparisons of P_L and flow patterns in the vaned diffuser showed that the matching optimization between the model B impeller outlet flow angle and diffuser inlet vane angle resulted in a better flow pattern in both the circumferential and axial directions of the diffuser, which leads to the P_L3 reduction. The meridian velocity V_m of model B was significantly increased at diffuser inlet regions and resulted in improvements of flow patterns at diffuser middle and outlet regions as well as pressure expansion capacity. Finally, the comparisons of P_L and flow characteristics in the volute showed that the turbulence loss reduction in the model B volute was due to the flow pattern improvement at diffuser outlet regions which provided better flow conditions at volute inlet regions. The matching optimization between the diffuser and volute significantly reduced the turbulence loss in volute sections 1–4 and enhanced the pressure expansion capacity in sections 8–10.