Effect of effective flow area ratio of impeller outlet and inlet on the performance of super-low specific speed centrifugal pump

Abstract

Under the condition that the main geometric parameters of pump remained unchanged, the optimization of pump performance was realized by reducing the effective flow area ratio of impeller outlet and inlet. The effective area ratio of impeller outlet and inlet was changed by means of quasi orthogonal method. With super-low specific speed centrifugal pump M23-12.5 as the research object, on the basis of the pump test results, the paper constructed 7 different impellers which were different effective flow area ratios and were loaded into the same complete casing geometric model including the front and back of the pump cavity and the seal rings. With CFD method, this paper analyzed the effect of different effective flow area ratios of impeller outlet and inlet on the performance and the distribution of flow field structure of super-low specific speed centrifugal pump. The results showed that with the impeller effective flow area ratio decreased, head and shaft power had a decline in varying degrees at the same time efficiency increased. Thus on the premise of improving efficiency, area ratio should be reduced appropriately; with the further narrowing of the impeller flow passages the internal axial vortex flow and the hydraulic loss became smaller; because the absolute speed of the impeller exit increasing after the passages narrowing, vortex near the tip clearance of impeller was enhanced and hydraulic loss was increased.