Multiphysics Analysis of Gas-Liquid Interaction in Triple-Screw Pumps: Impacts of Gas Volume Fraction on Transient Flow Dynamics and Rotor Mechanical Response.

Abstract

The flow characteristics of gas-liquid two-phase flow significantly impact the operational efficiency of triple-screw pumps, playing a crucial role in the optimization of structural design and assembly of these pumps. To investigate the influence of gas volume fraction on the flow field and rotor of a triple-screw pump, a transient simulation analysis of the flow field in the multiphase triple-screw pump under different gas volume fraction conditions was conducted based on the Eulerian-Eulerian heterogeneous flow model and the immersed solid method. Furthermore, a mechanical simulation analysis of the rotor was performed based on the obtained results. The simulation results indicate that the pressure within the pump increases in a stepwise manner along the axial direction and remains stable within the chambers. However, with the increase of the gas volume fraction, the pressure in the same spiral groove exhibits a trend of first decreasing and then increasing, with the lowest pressure observed at a gas volume fraction of 50%. When the gas volume fraction is below 30%, the gas is primarily distributed near the root of the male rotor and the meshing region between the male and female rotors. However, when the gas volume fraction exceeds 30%, the gas gradually fills the entire chamber. The liquid phase exhibits relatively high flow velocities in the rotor meshing zone and near the crest of the male rotor threads. At a gas volume fraction of 30%, the radial and circumferential deformations of the female rotor reach their maximum at the outlet of the final-stage chamber, with peak compressive deformations of 0.052755 and 0.0538754 mm, respectively. Meanwhile, the helical grooves on both sides exhibit axial deformations in opposite directions. In contrast, the male rotor experiences no significant deformation due to the axisymmetric force distribution exerted by the flow field. The variation in gas volume fraction significantly influences the pressure within the pump chamber, the distribution of the gas phase, and the velocity of the liquid phase, thereby affecting the deformation characteristics of the rotor.