EFFECT OF DIFFUSER INLET WIDTH ON CANTILEVER MULTISTAGE CENTRIFUGAL PUMP

Abstract

Five diffusers with different axial widths were constructed based on the area ratio principle to solve the problem that axial dimension errors of impeller and diffuser strongly affect the external performance and internal flow of a cantilever multistage centrifugal pump. Field calculations on a two-stage centrifugal pump were performed using the RNG k-? turbulence model on ANSYS Computational Fluid X. External characteristic experiments were also conducted to benchmark the numerical calculation. The external performance and velocity distribution in the different pump models were determined. Results show that when the diffuser inlet width is less than the impeller outlet width, an increase in the diffuser inlet width always causes a reduction in the pump head, and the pump efficiency increases at a small flow rate but decreases at a large flow rate. When the diffuser inlet width is larger than the impeller outlet width, the pump head and efficiency decrease constantly, and the rate of decrease increases gradually. The core zone and turbulent boundary exist in the front pump cavity. With an increase in the diffuser inlet width, the non-dimensional circumferential component velocity in the core zone reduces gradually, the effect of turbulent boundary on the flow in the core zone weakens slowly, and the non-dimensional radial component velocity is always approximate to zero. This study provides a new reference for the matching design between impeller and diffuser. Keywords: Multistage centrifugal pump, inlet width, diffuser, front pump cavity