The effects of balancing holes on the axial force of a centrifugal pump in the reverse mode

Abstract

Centrifugal pumps can feasibly act as turbines in small hydropower plants. However, prediction and reduction methods of axial force is still challenging. A proposed method to this goal is the use of balancing holes. Accordingly, this paper investigates the effect of balancing holes diameter on the hydraulic performance and the axial force of a centrifugal pump as turbine (PAT). In this study, modeling of the fluid flow within the pump was carried out by using the commercial software of Ansys CFX R19.0 and the SST turbulence model. The numerical results showed that by working in the reverse mode, the operating flowrate, head and the axial force of the pump are increased remarkably. This study proved that drilling balancing holes in the impeller, despite being simple, is a useful method in reducing the axial force and has minor effects of the output power. Results showed that by drilling a hole of diameter 2 mm, the axial force is approximately decreased by 60 % in almost all flowrates. Finally, it is observed that increasing holes diameter is mostly influential at high flowrates, and with diameter of 6.5 mm, the axial force is reduced about 90%.