Investigation of the axial force on a varying-speed centrifugal pump impeller

Centrifugal impeller has high efficiency but obvious axial force problems because of the axial-to-radial flow direction change. It is easy to cause the over loading of thrust bearing and damage shaft system. Especially in varying-speed centrifugal pumps, the mechanism, characteristics, and influence of impeller axial force is complex. Therefore, experimental and numerical studies are conducted to resolve these problems in this case. The impeller axial force is comparatively investigated by analyzing zonal components, visualizing internal flow, and resolving pressure attenuation law in clearances. This study provides a new test scheme based on force sensors for measuring the impeller axial force. The results show that the variation tendency of impeller axial force is similar to that of pump head. Flow patterns show that streamline-rotation angle decreases with the increase of flow rate in clearances. As the key factor affecting impeller axial force, the static pressure distribution in the clearances can be divided into specific variation stages to specify the mechanism. Specially in this varying-speed case, the blade axial force shifts from positive to negative with the decrease of rotation speed from high to low. This study provides a good reference for solving the axial force problems for centrifugal pumps.