Research On Collection Efficiency And Pressure Drop Of A Particle-loaded Single Fiber

Pressure drop and collection efficiency are very important performance parameters of fibrousfilter. Studying the filtering mechanism of a single fiber is particularly important to getperformance parameters of fibrous filter. Research on a single fiber filtration can be divided intosteady state and unsteady state,and previous study and experiments have shown that unsteady stateis more realistic.Domestic and foreign scholars have been studying unsteady filtration of a singlefiber for many years.There are several models in previous studies used to predict the pressure dropand collection efficiency of a single filter during the unsteady filtration state, but most of them arenot complete and accurate.Besides,experiment can’t explain the changes of fiber morphology,collection efficiency and pressure drop during the unsteady filtration state concretely andvividly.Therefore, the computer simulation of a single fiber filtration on unsteady state hasimportant significance,so this paper studies the changes of collection efficiency and pressure dropon single fiber filtration process under the two-dimensional and three-dimensional case,andfocuses on the unsteady state.In order to obtain more realistic models of single fiber branch during unsteady filtrationprocess,this article use the programs which is based on Kuwabara flow field to produce singlefiber branch model on each stage of unsteady filtration process.Then,through the CAD to revisethese models to make them can be simulated in Fluent.At last,use the DPM(discrete phasemodel)method to do numerical simulation study on pressure drop and collection efficiency ofsingle fiber.The major studies and conclusions are as follows:(1) Use the programs which based on Kuwabara flow field to produce single fiber branchmodel on each stage of unsteady filtration process.Through CFD methods to simulate the flowfield of these models,and use DPM method to get the models’ collection efficiency to analysis theimpact of particle dendrites on collection efficiency and pressure drop of a single fiber.(2) Based on the DPM simulation technique to simulate the collection efficiency and pressure drop of a two-dimensional single fiber model during unsteady filtering state.The resultsshow that with the continuous deposition of particles on the surface of a single fiber,thedimension,equivalent diameter and the maximum block area on the windward side of the modelsare all increase,so does the collection efficiency and pressure drop.The results also shows that thechanges of collection efficiency and pressure drop are more relevant with the changes of themaximum block area on the windward side of the models,it means that the dispositionmorphology which has a greater block district on the windward side is conductive to capturingparticles,and the pressure loss also become greater.(3) Through the DPM simulation technique to discuss the impact of particle dendrites oncollection efficiency and pressure drop of a three-dimensional single fiber, during the unsteadyfiltering state.The effects of Stokes number, dimensionless particle diameter St and particledendrites morphology on collection efficiency were investigated. The results show that thecollection efficiency of a single fiber strongly depends on Stokes number in the early stage of thedeposition, simulation cases with higher value of the St number has greater efficiency.；as theprocess of deposition going on,the collection efficiency and pressure drop of a single fiber bothincreases with the number of particles on the fiber,and the growing relationship and speed dependon the value of St number,Refand Nr. In addition,the disposition morphology that has a greaterblock district on the windward side is conductive to capturing particles and create greater pressureloss.And gives the collection efficiency relational5-4which applies to the unsteady filtering state.