Numerical Simulation Of Dispersion Process Of SiC Particles In Aluminum Melt Under Stirring

SiC particle reinforced aluminum matrix composites are considered to be one of the most competitive composites because of their excellent mechanical properties such as high specific strength,high specific stiffness,high wear resistance and good machinability.Liquid metal stirring method is widely used in the preparation of the composite.Among them,the flow field in the stirring container and the dispersion behavior of SiC particles directly affect the comprehensive properties of the composite.The exploration of them can provide a reference for the industrial application of liquid metal stirring method in the preparation of composite materials.In this thesis,aiming at the two-phase flow system of SiC particles and fluid under the action of mechanical stirring,taking ansys-fluent as the simulation platform,the geometric model of stirring vessel is established,and the relevant mathematical model is established.The feasibility of numerical simulation is verified by comparing the measured water simulation experiment with the numerical simulation results.The VOF（volume of fluid）method is used to simulate the free surface fluctuation and flow field characteristics in the stirred vessel,and the influence of the flow field on the movement and dispersion of SiC particles is qualitatively analyzed;The mixing characteristics of gas liquid solid three-phase flow under different SiC particle feeding modes are simulated and analyzed by Euler method.The relative standard deviation（RSD）is introduced to evaluate the dispersion degree of SiC particles,explore the influence of impeller speed and immersion depth on SiC particle distribution,and quantitatively study the dispersion of SiC particles;The discrete phase model（DPM）based on Euler Lagrange method is used to study the spatial dispersion process and motion trajectory of SiC particles in the flow field.The main results are as follows:At the initial stage of mixing,there is a brief upwelling at the center of the free surface.With the progress of mixing,the free surface drops and finally forms a stable V-shaped vortex;The maximum velocity of fluid medium flow in the vessel is located at the end of the impeller blade;The annular flow region in the flow field is conducive to the movement and dispersion of SiC particles,and the low velocity region at the bottom of the container hinders the dispersion of particles;At the initial time,the feeding mode of SiC particles evenly tiled above the free surface has better particle dispersion effect after the mixing reaches a steady state,and the feeding mode of bottom tiled is less effective;Increasing the impeller speed and immersion depth is conducive to the dispersion of SiC particles in the container.When the impeller speed is 410r·min^-1 and the immersion depth is 65mm,the dispersion effect of SiC particles is better,which is conducive to improving the quality of finished products;When the bottom of the free surface vortex reaches the upper end of the impeller,SiC particles begin to enter the rotating area of the blade and are dispersed.Under the action of the radial jet of the blade,SiC particles participate in the circulation of the flow field,so as to achieve the purpose of SiC particle dispersion.