Application of two-fluid model in the unsteady flow simulation for a multiphase rotodynamic pump

Abstract

Based on the assumption of tiny bubbly flow, the gas-liquid two-phase unsteady flow in a multiphase rotodynamic pump was numerically simulated with two-fluid model. The two-phase transport process and the evolution characteristic of the pump head were analyzed. In the working conditions, the liquid flow rate was constant, and the IGVF (inlet gas volume fraction) was 0.05, 0.15 and 0.25, respectively. The k ω− based SST model was used for turbulence; the drag force and the added mass force were accounted for in the interfacial momentum transfer terms. Because the wrap angle of the blade was large, the hybrid mesh was adopted to guarantee high mesh quality. The simulation results demonstrate that two-fluid model can more reasonably capture the transport process than the homogeneous model; and the drag law should be corrected based on the mixture viscosity in high gas volume fraction conditions. If the liquid flow rate is constant, the increase of IGVF can raise the pressure in the inlet extended region, while the pressure in the outlet extended region will not be affected much, thus the pump head will go down. In addition, due to the fluctuation of gas volume fraction field, the pump head will also fluctuate around a stable value in the transport process.