Numerical Investigation Of Submicron Particles Deposition On The Surface Of A Single Fiber

In order to reduce the emission of fine particulate pollutants from coal combustion,the electric bag integrated dust collector is widely used in the field of thermal power generation.Because of the filtration process of fiber filter containing complex interaction among fluid,particles and fibers,the unsteady dynamic deposition process of particles on single cylindrical and elliptical fiber is numerically simulated in order to get closer to the real physical process.We study and analyze the effects of particle properties and fiber parameters on the morphology of the particles on the surface of fiber and the properties of fiber-trapped particles detailedly.Firstly,the three main capture mechanisms of the particles in the deposition process and their respective principles of action are introduced.The numerical method used in the research of the deposition process of submicron particles on a single fiber is also introduced.Considering the interaction between particles and the effect of Brownian diffusion force on particles,a numerical model is established to determine whether particles collide with the surface of fiber in the flow field and whether they adhere or rebound after collision.Secondly,the numerical simulation method is used to study the trapping performance of a single cylindrical fiber for submicron particles.For different particle diameters,inflow velocities and fiber packing densities,the effects of these factors on the deposition morphology of particles and the capture performance of a single cylindrical fiber are analyzed.The results show that the dynamic deposition process of particles on a single cylindrical fiber under unsteady state can be mainly divided into the initial fiber capture stage,the subsequent dendritic structure of particles and the formation stage of particle chains.When the particle diameter increases from 0.5 to 1.0μm,the deposition morphology of particles gradually changes from uniform distribution to tree structure.Whend_p≥0.7 um,the formation of particle chains on the surface of fibers can be observed obviously.The fiber collection efficiency increases with the increase of the particle diameter.When the inlet flow velocity increases from 0.1 m/s to 0.8m/s,the deposition morphology of the particles changes significantly,and the fiber collection efficiency decreases gradually,reaching the lowest value at v_in=0.8 m/s.When the packing density of fiber increases from 2.8%to 8.2%,the collection efficiency and dimensionless pressure drop of fiber increase with the increase of SVF,and reach the highest value atd_f=25um.Finally,comparing the collection efficiency of single cylindrical fiber under optimum conditions with that of single elliptical fiber at four different deflection angles,it is found that the collection efficiency of single elliptical fiber is the highest when the deflection angle is 90^?.On this basis,the deposition process of submicron particles on a single elliptical fiber is numerically studied.The results show that the different deflection angles of single elliptical fiber has little effect on the deposition process of particles withd_p=0.5μm.However,for particles withd_p=0.8μm,the effect of different deflection angles of single elliptical fiber on the deposition process of fibers is more obvious,which is reflected in the maximum collection efficiency of fibers when?θ=90^?.The variation trend of the collection efficiency and dimensionless pressure drop of a single elliptical fiber caused by different particle diameters,inlet fluid velocities and fiber packing densities of fiber is similar to that of a single cylindrical fiber.However,it is obvious that the capturing performance of a single elliptical fiber is better than that of cylindrical fiber when the deflection angle is ?θ=90°.