Blade redesign based on secondary flow suppression to improve energy efficiency of a centrifugal pump

This paper conducts a systematic study to address the problems of high flow loss and low energy efficiency of centrifugal pumps caused by the development of secondary flow within the impeller. Based on the forces balance in the direction perpendicular to the streamline, theoretical calculations are drawn to redesign blade thickness for a 5-blade centrifugal impeller to suppress the secondary flow. The correlations between the development of internal secondary flow within the impeller and energy efficiency of centrifugal pump under full flow rate conditions are illustrated by numerical simulations validated by experimental tests. Secondary flow coefficient and entropy production rate (EPR) are introduced and extracted to quantitative analysis the secondary flow level and energy loss inside the impeller. Results indicate that the blade redesign methods proposed here can efficiently inhibit the development of secondary flow and improve the energy efficiency. Moreover, the secondary flow coefficient introduced in this paper can quantitatively reflect the intensity of secondary flow under various flow rates of different impellers. Combining with the entropy production analysis of impeller, the consistent change trend of total secondary flow coefficient and entropy production reveals that the improvement of pump energy efficiency benefits from the reduction of turbulence EPR which results from the suppression of internal secondary flow.