高湿黏性颗粒在聚四氟乙烯微孔膜滤料表面沉积特性的数值模拟

Numerical simulation of deposition characteristics for high moisture viscous particles on the surface of polytetrafluoroethylene microporous membrane filtration materials

基于聚四氟乙烯(PTFE)微孔膜滤料扫描电镜(SEM)图像,建立PTFE微孔膜滤料微观结构模型,采用计算流体力学和离散单元法(CFD-DEM)耦合的方法对黏性颗粒在微孔膜滤料表面沉积特性进行模拟,引入液桥力模型,忽略范德华力的作用,统计计算域内颗粒的受力情况,分析了不同表面能条件下3~6μm粒径颗粒在微孔膜滤料表面的沉积特性,将模拟结果与黏附效率的经验公式进行对比。结果表明,黏附效率与经验值、颗粒受力与液桥力模型的相对误差均在6%以内,CFD-DEM耦合计算方法可用于模拟不同环境湿度条件下的颗粒沉积;过滤风速、粒径与黏性是影响沉积形态的重要因素,提高过滤风速及增大颗粒粒径与黏性,颗粒更易在滤料表面形成稳定的树突结构,黏附效率及含尘压降增加。环境相对湿度影响两物体间液桥体积,接触力影响颗粒沉积,当增加表面能与液桥体积时,接触力及液桥力均相应增加,根据受力平衡原理,环境相对湿度对颗粒沉积影响很大。

Based on the scanning electron microscopy(SEM)image of polytetrafluoroethylene(PTFE)microporous membrane filtration material,the microstructure model of PTFE filtration material was established,and the coupling method of computational fluid dynamics and discrete element method(CFD-DEM)was used to simulate the deposition of the viscous particles on the surface of microporous membrane.In addition,the force of the particles in the calculation domain was calculated by introducing the liquid bridge force model and without considering the effect of Van der Waals force.Then the deposition characteristics of 3~6μm particles on the surface ofmicroporous membrane at different surface energies were analyzed,the simulation results were compared with the empirical formula of adhesion efficiency.The results showed that the relative errors between adhesion efficiency and empirical value,the force of particles and liquid bridge force model were less than 6%,which indicated that the CFD-DEM coupling method can be used to simulate particle deposition under different environmental relative humidity conditions.Filtration velocity,particle size and viscosity were important factors affecting the deposition morphology.When the filtration velocity,particle size and viscosity increased,the particles were more likely to form a stable dendritic structure on the surface of the filter material,which made the adhesion efficiency and dust-containing pressure drop increased.The environmental relative humidity affected the volume of liquid bridge between two objects,and the contact force affects the deposition of particles.With the increase of the surface energy and liquid bridge volume,contact force and liquid bridge force increased correspondingly.The environmental relative humidity had a great influence on the deposition of particles,according to the principle of force balance.