Numerical and Experimental Investigations of a Double-Suction Pump With a Middle Spacer and a Staggered Impeller

Double-suction pumps are among the most commonly used mechanical devices in irrigation and drainage. To investigate the effects of the impeller configuration with a spacer and staggered arrangement on the internal flow field and radial force characteristics of a double-suction centrifugal pump, a comparison investigation was conducted using the same type of pump with three different impeller configurations: a symmetrically arranged impeller without a spacer, a symmetrically arranged impeller with a spacer and a staggered 25° arrangement impeller with a spacer. This study employed a combination of experimental and numerical simulation methods to analyse changes in the head, efficiency, transient radial force and internal flow field under three typical operating conditions. The results indicate that the staggered 25° arrangement impeller with a spacer results in a higher head and efficiency than both the symmetrically arranged impellers without a spacer and those with a spacer across most working conditions. Furthermore, the efficiency improvement is most significant at low flow rates for the staggered 25° arrangement impeller with a spacer compared with the other configurations. In terms of the internal flow field, the addition of a spacer and staggered 25° arrangement impeller effectively reduces the high-velocity flow, making the pressure distribution gradient more reasonable and the turbulent kinetic energy distribution more uniform. Additionally, adding spacers and employing staggered arrangements effectively reduces the steady-state radial forces as well as the main frequency amplitude of the radial force fluctuations on the impeller. This improves both the high-velocity flow structure attenuation rate and outlet flow stability for double-suction impellers. By comparing and analysing the external characteristics, internal flow field and radial force characteristics of different impeller configurations, this study proposes an improved impeller scheme based on a spacer and staggered arrangement, which provides a new optimization idea for improving the efficiency and stability of double-suction centrifugal pumps in irrigation systems.