Effects of Particle Concentration on the Dynamics of a Single-Channel Sewage Pump under Low-Flow-Rate Conditions

Abstract

Single-channel sewage pumps are generally used to transport solid-liquid two-phase media consisting of a fluid and solid particles due to the good non-clogging property of such devices. However, the non-axisymmetric structure of the impeller of this type of pumps generally induces flow asymmetry, oscillatory outflow during operations, and hydraulic imbalance. In severe cases, these effects can jeopardize the safety and stability of the overall pump. In the present study, such a problem is investigated in the framework of a Mixture multiphase flow method coupled with a RNG turbulence model used to determine the structure of the flow field and the related motion of transported particles. It is shown that under different inlet particle concentrations, the flow field in the pump exhibits periodic variations of the pressure. The volume fraction of solid particles at the trailing edge of the suction surface of the blade is the largest, and solid particles tend to be concentrated at the outer edge of the pump body. With a rise in import particle content, the pressure and volume fraction of particles in the sewage pump also increase; for a fixed inlet particle concentration, the pressure pulsation amplitude increases with an increase in the flow rate. In addition, under small flow conditions, as the inlet particle concentration increases, the flow field leaving the sewage pump diaphragm near the outlet of the volute becomes more turbulent, and even a secondary back-flow vortex appears.