椭圆纤维过滤压降与惯性捕集效率数值分析
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摘要
采用数值方法求解了描述椭圆截面纤维绕流特征的Navier-Stokes方程,并计算了椭圆纤维对粒子惯性捕集效率及纤维过滤压降.分析讨论了椭圆纤维迎风角度θ、长短轴比ε和填充率C等参数对惯性粒子过滤性能的影响.结果表明,在大迎风角度时,过滤压降随长短轴比增大而增大,而在小迎风角度下,过滤压降则随长短轴比增大而减小;在相同纤维长短轴比条件下,过滤压降均随迎风角增大而增加.粒子惯性捕集效率计算结果则表明,对于中高惯性粒子捕集,大迎风角度和高长短轴比的椭圆纤维的捕集效率高于圆截面纤维,而对弱惯性粒子,小迎风角度和高长短轴比的椭圆纤维则表现出较高的捕集效率.在椭圆纤维过滤压降和捕集效率计算基础上,采用纤维过滤质量因子(定义为捕集效率比过滤阻力)评价综合过滤性能.结果表明,对于中高惯性粒子过滤,扁长型椭圆纤维(即为高长短轴比ε)在迎风角约为θ=45°时质量因子总体较高,即具有较优的综合过滤性能;而对弱惯性粒子,则扁长型椭圆纤维长轴平行来流方向(θ=0°)时,总体过滤性能较优.
A numerical scheme was developed for calculating the inertial collection efficiencies of particles by elliptical fibers andfiltration pressure drop. The viscous flow fields for single elliptical fiber were determined by solving the Navier-Stokes equationnumerically, and the effects of the following parameters, such as orientation angle(θ), cross-section aspect ratio(ε) and packingdensity(C) on the filtering performance were discussed. The results showed that the filtration pressure drop for elliptical fibersincreased with the increasing aspect ratio for large orientation angle but decreased for small orientation angle. With the samecross-section aspect ratio, the filtration pressure drop increased with the increasing orientation angle. The efficiency of ellipticalfibers with larger orientation angle and cross-section aspect ratio was higher than that of circular fibers for intermediate andhigh-inertia particles, whereas for low-inertia particles, the elliptical fibers with small orientation angle showed higher collectionefficiency. The quality factor, an indicator of the ratio of the collection efficiency to the pressure drop, was used to evaluate thecomprehensive performance of the elliptical fibers. It was found that the elliptical fibers with large aspect ratios(i.e., long and slimelliptical fibers) showed higher the quality factor(i.e., better comprehensive filtration performance) in capturing intermediate andhigh-inertia particles when the orientation angle was about θ=45°. For low-inertia particles, the elliptical fibers with major axisparallel to the incoming flow might have filtration performance advantages.
A numerical scheme was developed for calculating the inertial collection efficiencies of particles by elliptical fibers andfiltration pressure drop. The viscous flow fields for single elliptical fiber were determined by solving the Navier-Stokes equationnumerically, and the effects of the following parameters, such as orientation angle(θ), cross-section aspect ratio(ε) and packingdensity(C) on the filtering performance were discussed. The results showed that the filtration pressure drop for elliptical fibersincreased with the increasing aspect ratio for large orientation angle but decreased for small orientation angle. With the samecross-section aspect ratio, the filtration pressure drop increased with the increasing orientation angle. The efficiency of ellipticalfibers with larger orientation angle and cross-section aspect ratio was higher than that of circular fibers for intermediate andhigh-inertia particles, whereas for low-inertia particles, the elliptical fibers with small orientation angle showed higher collectionefficiency. The quality factor, an indicator of the ratio of the collection efficiency to the pressure drop, was used to evaluate thecomprehensive performance of the elliptical fibers. It was found that the elliptical fibers with large aspect ratios(i.e., long and slimelliptical fibers) showed higher the quality factor(i.e., better comprehensive filtration performance) in capturing intermediate andhigh-inertia particles when the orientation angle was about θ=45°. For low-inertia particles, the elliptical fibers with major axisparallel to the incoming flow might have filtration performance advantages.
引文
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[20]Wang W,Xie M,Wang L.An exact solution of interception efficiency over an elliptical fiber collector[J].Aerosol Science and Technology,2012,46(8):843-851.
[21]Lin K C,Patel R,Tsai J S.Filtration of aerosol particles by clean elliptical fibers with relevance to pore size:A lattice Boltzmanncellular automaton model[J].Computers&Fluids,2017,156(12):534-544.
[22]Jin X,Yang L,Du X,et al.Modeling filtration Performance of elliptical fibers with random distributions[J].Advanced Powder Technology,2017,28(4):1193-1201.
[23]Wang J,Pui D Y H.Filtration of aerosol Particles by elliptical fibers:a numerical study[J].Journal of Nanoparticle Research,2009,11(1):185-196.
[24]Wang H,Zhao H,Wang K,et al.Simulating and modeling Particulate removal Processes by elliptical fibers[J].Aerosol Science and Technology,2014,48(2):207-218.
[25]陈懋章.粘性流体力学基础[M].北京:高等教育出版社,2004:111-112.CHEN Maozhang.Fundamentals of viscous fluid dynamics[M].Beijing:Higher Education Press,2004:111-112.
[26]Lee K W,Liu B Y H.Theoretical study of aerosol filtration by fibrous filters[J].Aerosol Science and Technology,1982,1(2):147-161.
[27]朱辉,付海明,亢燕铭.单纤维过滤阻力与惯性捕集效率数值分析[J].中国环境科学,2017,37(4):1298-1306.ZHU Hui,FU Haiming KANG Yanming.Numerical Calculation and Analyses of pressure drop of a single fiber under dust-loaded conditions[J].Chinese Journal of Chemical Engineering,2012,63(12):3927-3936.
[28]Hinds W C.Aerosol technology:Properties,behavior,and measurement of airborne particles[M].New York:John Wiley&Sons,Inc.,2012:42-44.
[29]Brown R C.Air filtration:an integrated approach to the theory and applications of fibrous filters[M].New York:Pergamon Press,1993:32-34.
[30]Kuwabara S.The forces experienced by randomly distributed parallel circular cylinders or spheres in a viscous flow at small Reynolds numbers[J].Journal of the Physical Society of Japan,1959,14(4):527-532.
[31]Peter C R.Flow field and drag for elliptical filter fibers[J].Aerosol Science and Technology,2002,36(12):1118-1127.
[2]邵龙义,杨书申,赵厚银,等.室内可吸入颗粒物理化特征及毒理学研究[M].北京:气象出版社,2012:130-160.Shao Longyi,Yang Shushen,Zhao Houyin,et al.Physicochemistry and toxicology of indoor airborne inhalable particles[M].Beijing:China Meteorological Press,2012:130-160.
[3]谭成好,赵天良,崔春光,等.近50年华中地区霾污染的特征[J].中国环境科学,2015,35(8):2272-2280.TAN Chenghao,ZHANG Tianliang,CUI Chunguang,et al.Characterization of haze pollution over Central China during the past50years[J].China Environmental Science,2015,35(8):2272-2280.
[4]Wang H,He Q,Chen Y,et al.Characterization of black carbon concentrations of haze with different intensities in Shanghai by a three-year field measurement[J].Atmospheric Environment,2014,99:536-545.
[5]H?nninen O O,Palonen J,Tuomisto J T,et al.Reduction potential of urban PM2.5 mortality risk using modern ventilation systems in buildings[J].Indoor Air,2005,15(4):246-256.
[6]Yu B F,Hu Z B,Liu M,et al.Review of research on air-conditioning systems and indoor air quality control for human health[J].International Journal of Refrigeration,2009,32(1):3-20.
[7]Fisk W J,Chan W R.Effectiveness and cost of reducing particle‐related mortality with particle filtration[J].Indoor Air,2017,27(5):909-920.
[8]Liu G,Xiao M,Zhang X,et al.A review of air filtration technologies for sustainable and healthy building ventilation[J].Sustainable Cities and Society,2017,32:375-396.
[9]Li W,Shen S,Li H.Study and optimization of the filtration performance of multi-fiber filter[J].Advanced Powder Technology,2016,2(27):638-645.
[10]Yun K M,Suryamas A B,Iskandar F,et al.Morphology optimization of polymer nanofiber for applications in aerosol particle filtration[J].Separation and Purification Technology,2010,75(3):340-345.
[11]丁彬,俞建勇.静电纺丝与纳米纤维[M].北京:中国纺织出版社,2011:123-142.Ding bin,Yu Jianyong.Electrospinning and nanofibers[M].Beijing:China Textile Press,2011:123-142.
[12]Sanchez J R,Rodriguez J M,Alvaro A,et al.The capture of fly ash particles using circular and noncircular cross‐section fabric filters[J].Environmental Progress&Sustainable Energy,2007,26(1):50-58.
[13]Inagaki M,Sakai K,Namiki N,et al.Influence of fiber cross-sectional shape on filter collection performance[J].Kagaku Kogaku Ronbunshu,2001,27(1):113-120.
[14]顾丛汇,吕士武,李瑞,等.纤维对PM2.5过滤性能的影响[J].化工学报,2014,65(6):2137-2147.Gu Conghui,LüShiwu,Li Rui,et al.Influence of fiber on filtration performance for PM2.5[J].Chinese Journal of Chemical Engineering,2014,65(6):2137-2147.
[15]Das D,Ishtiaque S M,Das S.Influence of fibre cross-sectional shape on air permeability of nonwovens[J].Fibers and Polymers,2015,16(1):79-85.
[16]Hosseini S A,Tafreshi H V.On the importance of fibers'cross-sectional shape for air filters operating in the slip flow regime[J].Powder Technology,2011,212(3):425-431.
[17]Raynor P C.Single-fiber interception efficiency for elliptical fibers[J].Aerosol Science and Technology,2008,42(5):357-368.
[18]Regan B D,Raynor P C.Single-fiber diffusion efficiency for elliptical fibers[J].Aerosol Science and Technology,2009,43(6):533-543.
[19]Wang K,Zhao H.The influence of fiber geometry and orientation angle on filtration Performance[J].Aerosol Science and Technology,2015,49(2):75-85.
[20]Wang W,Xie M,Wang L.An exact solution of interception efficiency over an elliptical fiber collector[J].Aerosol Science and Technology,2012,46(8):843-851.
[21]Lin K C,Patel R,Tsai J S.Filtration of aerosol particles by clean elliptical fibers with relevance to pore size:A lattice Boltzmanncellular automaton model[J].Computers&Fluids,2017,156(12):534-544.
[22]Jin X,Yang L,Du X,et al.Modeling filtration Performance of elliptical fibers with random distributions[J].Advanced Powder Technology,2017,28(4):1193-1201.
[23]Wang J,Pui D Y H.Filtration of aerosol Particles by elliptical fibers:a numerical study[J].Journal of Nanoparticle Research,2009,11(1):185-196.
[24]Wang H,Zhao H,Wang K,et al.Simulating and modeling Particulate removal Processes by elliptical fibers[J].Aerosol Science and Technology,2014,48(2):207-218.
[25]陈懋章.粘性流体力学基础[M].北京:高等教育出版社,2004:111-112.CHEN Maozhang.Fundamentals of viscous fluid dynamics[M].Beijing:Higher Education Press,2004:111-112.
[26]Lee K W,Liu B Y H.Theoretical study of aerosol filtration by fibrous filters[J].Aerosol Science and Technology,1982,1(2):147-161.
[27]朱辉,付海明,亢燕铭.单纤维过滤阻力与惯性捕集效率数值分析[J].中国环境科学,2017,37(4):1298-1306.ZHU Hui,FU Haiming KANG Yanming.Numerical Calculation and Analyses of pressure drop of a single fiber under dust-loaded conditions[J].Chinese Journal of Chemical Engineering,2012,63(12):3927-3936.
[28]Hinds W C.Aerosol technology:Properties,behavior,and measurement of airborne particles[M].New York:John Wiley&Sons,Inc.,2012:42-44.
[29]Brown R C.Air filtration:an integrated approach to the theory and applications of fibrous filters[M].New York:Pergamon Press,1993:32-34.
[30]Kuwabara S.The forces experienced by randomly distributed parallel circular cylinders or spheres in a viscous flow at small Reynolds numbers[J].Journal of the Physical Society of Japan,1959,14(4):527-532.
[31]Peter C R.Flow field and drag for elliptical filter fibers[J].Aerosol Science and Technology,2002,36(12):1118-1127.
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