Flow structure in casing of closed-type centrifugal pump with single blade

As centrifugal pumps with a single blade can secure large passed particle size, they are widely used as sewage pumps transporting liquid containing foreign bodies. Not only dos the internal flow of centrifugal pumps with a single blade vary significantly according to the flow rate, but it also varies significantly according to the rotation of the impeller, and therefore it is extremely complex. Elucidation of this complex and unsteady internal flow is extremely important for enhancing efficiency by reducing loss and realizing high reliability by reducing the fluid force. This research has involved a structural survey of flow in the casing of closed-type centrifugal pump with a single blade through PIV measurement and CFD analysis. The study has showed that various vortexes were produced inside the casing by maximum efficiency point flow rate, and that a large scale vortex structure which varies significantly along with rotation of the impeller is formed. This suggests that increase or decrease of mixing loss inside the casing produced by rotation of the impeller does not depend on increase or decrease of vortex area inside the casing, but is rather produced by increase or decrease of vortexes produced near the tongue part and the beginning of the volute winding. © 2020, Turbomachinery Society of Japan. All rights reserved.