Abstract: Because of the existence of reflux hole in the self-priming centrifugal pump volute, its internal transient flow is more complicated than the ordinary centrifugal pump, and it largely determines the running stability. In order to study the transient flow characteristics inside a self-priming centrifugal pump volute, the three-dimensional unsteady flow under various operating conditions of a model pump with and without reflux hole were numerically simulated to investigate the volute pressure fluctuations and transient flow characteristics near the reflux hole. The results showed that the existence of reflux hole makes the volute pressure fluctuation more severe and variable. In the volute cross-sections with the largest pressure fluctuation amplitude, there were relatively strong, symmetrical, different sizes and reverse secondary flow vortexes. The vorticity was great at the exit of reflux hole to volute, and there were vortexes flow structures that change periodically over time in the cross-section of both directions. The maximum pressure pulsation amplitude of volute with reflux hole was larger than that without reflux hole. The increased amplitudes were, respectively, 35.5%, 13.7% and 19.6% under the conditions that flow rates were 0.8, 1.0 and 1.2 times of the design flow rate.

Key words: self-priming centrifugal pump, volute, reflux hole, transient flow characteristics, pressure fluctuation