Research On The Mechanism Of Micro-particle Collision And Coagulation

Particulate pollutants in ambient air are the main culprits affecting global climate and urban air quality,severe pollution will also bring various respiratory and cardiovascular diseases to human beings and seriously threaten human health.At present,it has been hotly debated around the world,and most countries have formulated relevant ambient air quality standards to regulate the discharge of atmospheric pollutants.The characterization of fine particles is an area of immense significance to many industrial endeavors.According to the survey,70% of all industrial processes deal with fine particles at some point.Aggregation is a natural phenomenon during these processes.How to predict the evolution of particle size distribution in the coagulation process has been an issue concerned by the scientific community.This thesis studied particle dielectrophoresis(DEP)interaction in a uniform DC electric field.The iterative dipole moment(IDM)algorithm is used for data calculation and dynamic motion simulation of external electric field-particle motion.The paper calculates and simulates the trajectories of particles with different sizes,as well as the trajectories of particles with different dielectric properties and the dielectric force.Neutral micro-nano particles are polarized into electric dipoles under the action of an external electric field to undergo dielectric electrophoresis,and they are assembled into particle chains or coagulated into clusters.It was found that homogeneous adjacent particles whose connection line isn’t perpendicular to the electric field will cluster parallel to the electric field,and homogeneous adjacent heterogeneous particles will cluster perpendicular to the electric field.On the one hand,the characteristics of particle dielectrophoresis and particle chain formation can be applied to particle assembly technology,which has reference application value in biomedicine and new material research.On the other hand,it is possible to ensure accuracy and efficiently analyze how micro-nano particles are assembled and condensed under the action of an external electric field,which is also the subject of current research by successive scholars.Then,based on the collision probability theory and convection-diffusion equation,the collision frequency function under the action of Brownian motion is derived.Based on the collision frequency function under the action of magnetic field,the collision frequency function of particles in free molecule region and Stokes region under electric field were derived.In addition,a study on the collision frequency function of ultrasonic coagulation of particles caused by sonic wake effects and Brownian motion is also presented.At last,based on the theoretical research of the collision frequency function,a numerical model of particle electrocoagulation was established.We first applied the TEMOM model to the study of micro-nanoparticle electrocoagulation.The analytical expressions of the nanoparticle number concentration and system polydispersity are derived and solved,and then the coagulation law of micro-nano particles under the action of an external electric field is studied.