Mechanism of cross-vane flow influence on the hydraulic performance of centrifugal pumps with half vaned diffuser

Half vaned diffuser has been shown to improve the efficiency of centrifugal pumps and shift the high-efficiency zone toward higher flow rates compared to full-height vaned diffuser. However, the mechanism underlying this performance enhancement remains unclear. This study integrates experimental data and numerical simulations to investigate how cross-vane flow influences the hydraulic performance of centrifugal pumps. Results indicate that using half vaned diffuser increases the maximum pump efficiency from 55.1% to 57.0% and broadens the high-efficiency flow rate range from 30.42–40.08 to 37.63–48.61 m3/h. Half vaned diffuser modifies the internal flow field of the volute by modifying its own flow characteristics, thereby substantially reducing the hydraulic losses of the volute. The mechanism by which half vaned diffuser reduces hydraulic losses lies in the presence of leakage flow and leakage vortices induced by cross-vane flow. These structures mitigate velocity and total pressure difference between pressure and suction surface, promote momentum exchange between end clearance and vaned region, and suppress and eliminate flow separation on the suction surface. Consequently, the formation of main vortex structure and backflow near the volute tongue is effectively eliminated, resulting in improved flow uniformity and reduced energy losses. Furthermore, cross-vane flow mitigates the non-uniform distribution of vorticity stretching and tilting term, and viscous diffusion term within the diffuser, weakening their influence on the formation of main vortex structure with a blocking effect in the volute. The viscous effect of the end face play an important role in improving the internal flow characteristics of half vaned diffuser-particularly within the end clearance-thereby enhancing the flow field near the volute tongue and suppressing the development of main vortex structures in the volute. These findings provide new insights into the flow physics of half vaned diffuser and offer guidance for improving centrifugal pump performance through diffuser design.