Study on the Influence of Cascade Density on Internal and External Characteristics of Multi-Blade Axial-Flow Pump Impeller

To study the influence of cascade density on the performance of the multi-blade axial-flow pump impeller, the mechanism of the variation of the impeller inlet and outlet velocity with cascade density based on mass flow weighting was revealed, and the variation of the impeller inlet and outlet pressure pulsation with cascade density was obtained. The SST krw turbulence model was used to numerically analyze the multi-blade axial-flow pump impeller with different cascade densities in two cases: specific chord length and specific pitch. The results show that the impeller head coefficient and shaft power are positively correlated with the cascade density and the efficiency is parabolic in a certain range; the impeller inlet pressure pulsation coefficient is negatively correlated with the increase of the cascade density, while the impeller outlet pressure pulsation coefficient is positively correlated with the increase of the cascade density; in addition, the increase of the cascade density can effectively increase the minimum pressure on the suction surface of the blade, which can significantly improve the cavitation performance of the impeller. For a specific pitch, the head coefficient reaches a maximum value of 0. 432 at a peripheral cascade density of 1. 53, and the efficiency reaches a maximum value of 93. 47% at a peripheral cascade density of 1. 21; for a specific chord length, the head coefficient reaches a maximum value of 0. 415 at a peripheral cascade density of 1. 42, and the efficiency reaches a maximum value of 93. 32% at a peripheral cascade density of 0. 89. At the same cascade density, the internal and external characteristics of the impeller in the two cases show obvious differences. This study can provide some reference for the selection of cascade density in the design of the multi-blade axial-flow pump impeller. © 2023 Xi'an Jiaotong University. All rights reserved.