摘要
为探究纤维过滤介质中纤维曲率对其内部速度分布、压力损失、过滤效率的影响,通过Digimat建模软件建立曲率K分别为 0、2、4、6,固体体积分数为 8%,在三维空间中随机分散排列的纤维过滤介质模型,结合计算流体力学方法,基于拉格朗日离散模型和Laminar流场,利用雷诺相似准则,设置入口速度分别为 0.05、0.142、0.5、1、2 m/s,平均颗粒粒径为 0.25、0.5、1、1.5、2.5、4、5 mm,对微米纤维模型内部气-固两相流动情况进行数值模拟.结果表明:随着纤维曲率K由 0 增大至 6,在入口速度为 0.5 m/s时,纤维曲率对速度场分布的影响不明显,速度场的分布呈无规律性;纤维曲率对模型内部压力损失有显著影响,随着纤维曲率的提高,纤维模型内部压力损失呈线性增大;纤维过滤介质的过滤效率随纤维模型曲率的增大而提高,在入口速度为 1 m/s、模型曲率K为 6 时,对平均粒径为 5mm的颗粒过滤效率接近 90%,明显高于相同粒径下K为 0 时的过滤效率.
Abstract
Objective In filtration simulation calculation for internal structure of fiber assemblies,the fiber filtration medium model established is limited to a single cylinder.Although this simplified model is conducive to the rapid solution of the problem,its limitation is that it cannot fully demonstrate the influence of multi-fiber structure on the filtration performance.In practical engineering applications,fibers in the assembly used for air filtration have axially curved structures,and are not completely cylindrical.If this factor is ignored,the simulated results will be inevitably different from the actual test results,and the filtration characteristics and internal pressure loss of the filter material can not be accurately described.In order to simulate and predict the properties of fiber filter media more accurately,more complex models need to be built to describe the internal structure of fiber assembly.This includes considering the bending and random arrangement of the fibers.The refined model will help understand furtherthe flow characteristics and filtration behavior of fiber filter media,improve the consistency of simulation results and actual test results,and provide a reliable scientific basis for the design and optimization of filter media in engineering applications.Method A three-dimensional fiber filter media model with curvature K=0,2,4 and 6,solid volume fraction of 8%,randomly distributed in space was established by Digimat modeling software.Combined with computational fluid dynamics methods,based on Lagrange discrete model and Laminar flow field,similarity principle and Reynolds similarity criterion were used.The inlet velocities were set as 0.05,0.142,0.5,1 and 2 m/s,respectively,and the average particle size was 0.25,0.5,1,1.5,2.5,4 and 5 mm.The gas-solid two-phase flow inside the micron fiber model was numerically simulated.Results As the fiber curvature K increases from 0 to 6,when the inlet velocity is 0.5 m/s,the distribution of the fiber in the filter region is irregular,random and asymmetrical,and the flow velocity distribution is also irregular,and the influence of curvature on the velocity field distribution is not obvious.With the increase of the curvature of the fiber model,the internal pressure loss of the fiber model increases linearly.The pressure value of the windward side of the fiber is greater than that of the leeward side,and the pressure loss when the curvature K is 6 is significantly greater than that when the curvature K is 0.The filtration efficiency of fiber filtration medium increases with the increase of model curvature.When the inlet velocity is 1 m/s and the curvature K is 6,the filtration efficiency of particles with an average particle size of 5 mm is close to 90%,which is significantly higher than the filtration efficiency of K=0 under the same particle size.This is because the curvature of the fiber increases and more bending and folding will appear on the fiber surface,which will increase the surface area of the fiber.The larger surface area of the fiber provides more opportunity for the fiber to contact with the dusty air stream,which makes it easier for the fiber to collide with particles in the air stream and trap them.In addition,the greater the curvature of the fiber body,the greater the degree of deformation and distortion of the fiber body.Thus,a more complex and disorganized stacking and crossing structure can be formed between adjacent fibers,and the pore size between adjacent fibers is smaller,so that the interception and trapping capability of a single fiber on particles will be greatly improved,and the overall filtration efficiency of the filter medium will also be improved.Conclusion The filtration efficiency and pressure loss of the fiber assembly increase with the increase of fiber curvature.In practical engineering applications,in order to improve the filtration capacity of the filter material,the filter material with more fold structure is used as far as possible to increase the filtration area and dust holding capacity of the filter material while ensuring the pressure loss as little as possible.The folded structure makes the fibers in the filter material show a high degree of non-uniformity.More interception sites and bending paths are created,effectively enhancing the interaction between particles and fibers,thereby improving the filtration efficiency of the filter material.
基金项目
国家自然科学基金项目(51803182)
浙江省"尖兵""领雁"研发攻关计划项目(2023C01194)
高等学校学科创新引智计划资助项目(D21011)
浙江理工大学基本科研业务费专项资金项目(22202304-Y)
NETL
NSTL
万方数据