Study On Free Settlement Characteristics Of Fiber Particles

In the textile industry,a large amount of fibrous particles are dispersed in the surrounding production environment.Most of these particles are in the form of elongated columns with large surface area and low density.Various movement characteristics occur when they settle down in the air,for example,horizontal and vertical translation,rotation and oscillation.Therefore,these fibrous particles cannot be effectively captured and purified,which will have a great impact on the relevant production processes,equipment and workers' operating environment.In order to more effectively control the large amount of fiber particles produced in the textile industry production process and further improve the working environment quality of the post workers,it is necessary to conduct in-depth research on the free sedimentation velocity and lateral migration characteristics of the fiber particles.In this paper,three common fibrous particles are studied,namely cotton fiber,jute fiber and glass fiber.The theoretical research and experimental test methods are used to complete the following research work:Firstly,the basic characteristics of fiber particles are expounded,and the movement mechanism of fiber particles in free settling motion in air is analyzed.The main factors that can affect the free sedimentation characteristics of fiber particles are determined.Secondly,the diameter and microstructure of fibrous particles were tested and characterized by polarized light microscopy.The hygroscopicity of fibrous particles was tested by saturated salt solution method.The test platform for fibrous particle sedimentation characteristics based on high-speed camera system was built.Several methods were applied to eliminate experimental errors and interference factors,and the best experimental test and analysis program were determined.Again,the test of the settlement motion of the fiber particles under various working conditions was completed.On the one hand,the sedimentation velocity and lateral migration of the fiber particles during the sedimentation process were obtained.The main conclusions are as follows: as for the sedimentation velocity of fibrous particles,under different length-to-diameter ratios and different relative humidity,the relationship between the free sedimentation velocity of the three kinds of fibers is: jute fiber>glass fiber>cotton fiber.When length-to-diameter and relative humidity of the environment increase,the sedimentation velocity of jute fiber increases,and the effect of length-to-diameter on the free settling velocity of jute and glass fiber is more sensitive than that of environmental relative humidity;when length-to-diameter increases,the settling velocity of glass fibrous particle shows a significant increasing However,for the cotton fiber,the increase of the length-to-diameter causes the free sedimentation velocity of the cotton fiber to decrease,and the increase of environment relative humidity causes the free sedimentation velocity to increase first and then decrease.The main reason is that the average angle between the main axis of the fiber particles and the direction of gravity increases as in the process of free sedimentation,so that the projected area of the cotton fiber particles in the sedimentation direction increases,and the resistance of the air increases.Due to the good hygroscopicity,the free sedimentation rate of cotton fiber and jute fiber particles increases with the increase of moisture absorption rate.In addition,for the lateral migration of fiber particles in the sedimentation process,when the initial orientation of the particles is horizontal,the dimensionless lateral migration displacement of the three kinds of particles varies from-34% to 26% under different aspect ratios and relative humidity.Additionally,the absolute value of the particles' displacement is also analyzed,and it varies from 0 to 12% for 75.33% of them;With the increase of relative humidity,the lateral migration of cotton fiber and jute fiber particles decreases,However,no obvious regularity was found to glass fiber due to poor hygroscopicity.When the environment relative humidity is constant,the lateral migration displacement of cotton,jute and glass fiber particles decreases in turn;while the aspect ratio of the three fiber particles increases,the lateral migration displacement does not show obvious regularity.,indicating that the correlation between the aspect ratio and the lateral migration displacement is poor.On the other hand,combined with the above theoretical analysis and experimental test results,the optimum equivalent diameter suitable for characterizing the fiber particles was established,and the jute fiber was used.For example,the theoretical expression of the drag coefficient is established.