Effect of Tip Clearance on the Cavitation Performance of a Helical Blade Transfer Pump

The internal flow characteristics of the self-developed helical blade transfer pump under multiple working conditions and different tip clearances were compared and analyzed using the Zwart-Gerber-Belamri model based on the Rayleigh-Plesset equation for a detailed study of the influence of tip clearance on the cavitation performance of helical blade transfer pump. The results showed that more obvious cavitation is observed for larger blade tip clearance. Additionally, the cavitation gradually developed from the blade pressure surface to the flow channel with increased blade height, blocking the flow channel. According to the distribution under different vortex and cavitation conditions, increasing cavitation at the blade tip clearance helps increase the fluid flow stability at the clearance. However, from the perspective of the change in the overall vorticity, cavitation accumulation inhibits the reduction of vorticity and increases fluid instability. The increased tip clearance makes up for the pressure difference caused by the unsteady flow to some extent. However, the increased leakage flow caused by the increased tip clearance promotes the formation of tip clearance leakage vortex in advance. Furthermore, the cavitation in the flow channel appears closer to the pressure surface of the tip clearance due to the corresponding relationship between the cavitation and secondary leakage vortex areas in the flow channel.