Numerical study of the effect of droplet coagulation on the dynamics of a two-fraction aerosol in an acoustic resonator

The study is devoted to the study of the effect of coagulation of dispersed phase droplets on aerosol oscillations in an acoustic resonator. The mathematical model of aerosol dynamics implements a continuous mathematical model of the dynamics of a multiphase medium, taking into account the velocity and thermal inhomogeneity of the mixture components. To describe the dynamics of the carrier medium, a two-dimensional unsteady system of Navier – Stokes equations for a compressible gas is used, written taking into account the interphase force interaction and interphase heat transfer. To describe the dynamics of the dispersed phase, a system of equations is solved for each of its fractions, including the continuity equation for the «average density» of the fraction, the equations for the conservation of the spatial components of the momentum and the equation for the conservation of thermal energy of the fraction of the dispersed phase of the gas suspension. The interphase force interaction included the Archimedes force, the force of the added masses and the force of aerodynamic drag. The heat exchange between the carrier medium - gas and each of the dispersed phase fractions was also taken into account. The mathematical model of the dynamics of a polydisperse aerosol was supplemented by a mathematical model of collisional aerosol coagulation. For the velocity components of the mixture components, uniform Dirichlet boundary conditions were specified. For the remaining functions of the dynamics of the multiphase mixture, homogeneous Neumann boundary conditions were specified. The equations were solved by the explicit McCormack method with a nonlinear correction scheme that allows obtaining a monotonic solution. As a result of numerical calculations, it was determined that a region with an increased content of coarse particles is formed in the vicinity of the oscillating piston. The coagulation process leads to a monotonic increase in the volumetric content of the fraction of coarse particles and a monotonic decrease in the volumetric content of fine particles.

Analysis of flow and phase interaction characteristics in a gas-liquid two-phase pump

To analyze the characteristics of internal flow and phase interaction in a gas-liquid two-phase pump, the influence of Inlet Gas Void Fraction (IGVF), discharge coefficient, and medium viscosity were investigated using medium combinations of air-water and air-crude. Simulations were performed using ANSYS_CFX at different IGVFs and various values of discharge coefficient. Structured grid for the full flow passage was generated using ICEM_CFD and TurboGrid. Under conditions of IGVF = 0% (pure water) and IGVF = 15%, the reliability of numerical method was proved by means of the comparison with the experimental data of external characteristic. The results for air-water combination showed a uniform gas distribution in the inlet pipe, and formation of a stratified structure in the outlet pipe. The gas in impeller gathered at the hub because of the rotation of the impeller, also, the interphase forces increased with the increased IGVF. For the two medium combinations, the drag force was the largest interphase force, followed by added mass and lift forces, and then the turbulent dispersion force was the least, which can be neglected. Because of the larger viscosity of crude than that of water, the variation trend of interphase forces in the impeller is relatively smooth along the flow direction when the medium combination was air-crude.

Study on Entrainment Force between Phases Perpendicular to Horizontal Flow Direction in Gas-Liquid Two-Phase Flow

In this paper, the theoretical model of entrainment force perpendicular to horizontal flow direction in gas-liquid two-phase flow was researched, then the entrainment forces were acquired by the interphase force detection device on the experimental device of gas-liquid two-phase, with working pressure of 0.05, 0.10 and 0.15MPa. The characteristics of entrainment force was analyzed at last. The results showed that the variation of entrainment force between phases obtained by experiment was in good agreement with theoretical analysis, moreover no correlation with working pressure.

Study on Interphase Force Quantitative Detection Device of Horizontal Pipe Gas-Liquid Two-Phase Flow

The paper focuses on the interphase force of the gas-liquid two-phase flow in the horizontal pipe design and designs a new interpahse force quantitative detection devices. On the basis of analyzing the physical models and the mathematical models, the devices got the more accurate differential pressure and the two-phase flow phase holdup, avoiding many factors by using the capacitance sensor which is made up of the complete closure outer electrode and flow media as the inner electrode. Finally, the devices achieved the quantitative detection of the interphase force through the differential pressure and the phase holdup. The experiments proved that the devices can better reflect the interphase force changes of the gas-liquid two-phase flow in the horizontal tube and reached the design goal very well.