1～3 nm颗粒物在粒径分布测量仪中的通过效率研究
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摘要
基于二甘醇的扫描电迁移率粒径谱仪(DEG-SMPS)是常用的1～3 nm颗粒物粒径分布测量系统.目前对1～3 nm颗粒物在该系统中通过效率的量化不够准确,这给大气颗粒物粒径分布的测量带来了较大的不确定性.本文研究了1～3 nm颗粒物和离子在直管、弯管以及气溶胶中和器等系统组件中的通过效率,并使用等效管长法来量化颗粒物在这些组件单元中的通过效率.研究表明,1～3 nm颗粒物在直管内的通过效率不受颗粒物电性影响,且可以由Gormley-Kennedy (G-K)方程估算.当采样流量为2.5 L·min~(-1)时,DEG-SMPS系统中总等效管长约为433 cm,其中气溶胶中和器的等效管长为160 cm,弯头的等效管长为33 cm.
Diethylene glycol scanning mobility particle spectrometer(DEG-SMPS) system has been used for measuring the size distribution of 1～3 nm particles. However, penetration efficiency of 1～3 nm particles in DEG-SMPS is not accurately calculated, which increases the uncertainty of the measured 1～3 nm particle size distributions. In this study, the penetration efficiencies of 1～3 nm tungsten oxide particles and ions through different devices before entering the detector, including straight tubes, elbows, and an aerosol neutralizer are calibrated and the equivalent length method is used to describe particle penetration through these devices. The penetration efficiency through a straight tube can be estimated using the Gormley-Kennedy formula and it is negligibly affected by the charging polarity. At the sampling flow rate of 2.5 L·min~(-1), the equivalent length for the whole DEG-SMPS system is 433 cm, and for aerosol neutralizer and elbows are 160 cm and 33 cm, respectively.
Diethylene glycol scanning mobility particle spectrometer(DEG-SMPS) system has been used for measuring the size distribution of 1～3 nm particles. However, penetration efficiency of 1～3 nm particles in DEG-SMPS is not accurately calculated, which increases the uncertainty of the measured 1～3 nm particle size distributions. In this study, the penetration efficiencies of 1～3 nm tungsten oxide particles and ions through different devices before entering the detector, including straight tubes, elbows, and an aerosol neutralizer are calibrated and the equivalent length method is used to describe particle penetration through these devices. The penetration efficiency through a straight tube can be estimated using the Gormley-Kennedy formula and it is negligibly affected by the charging polarity. At the sampling flow rate of 2.5 L·min~(-1), the equivalent length for the whole DEG-SMPS system is 433 cm, and for aerosol neutralizer and elbows are 160 cm and 33 cm, respectively.
引文
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Wilson S R,Liu Y,Matida E A,et al.2011.Aerosol deposition measurements as a function of reynolds number for turbulent flow in a ninety-degree pipe bend [J].Aerosol Science and Technology,45(3):364-375
Cai R,Chen D R,Hao J,et al.2017.A miniature cylindrical differential mobility analyzer for sub-3 nm particle sizing [J].Journal of Aerosol Science,106:111-119
Covert D,Wiedensohler A,Russell L.1997.Particle charging and transmission efficiencies of aerosol charge neutralizes [J].Aerosol Science and Technology,27(2):206-214
De la Moja J F,Kozlowski J.2013.Hand-held differential mobility analyzers of high resolution for 1～30 nm particles:design and fabrication considerations [J].Journal of Aerosol Science,57(2):45-53
Fu Y,Xue M,Cai R,et al.2019.Theoretical and experimental analysis of the core sampling method:Reducing diffusional losses in aerosol sampling line[J].Aerosol Science and Technology,53(7):793-801
Gormley P G,Kennedy M.1948.Diffusion from a stream flowing through a cylindrical tube [J].Procroyirish Acada,52:163-169
Jiang J,Chen M,Kuang C,et al.2011.Electrical mobility spectrometer using a diethylene glycol condensation particle counter for measurement of aerosol size distributions down to 1 nm [J].Aerosol Science and Technology,45(4):510-521
Kangasluoma J,Franchin A,Duplissy J,et al.2016.Operation of the airmodus A11 nano condensation nucleus counter at various inlet pressures and various operation temperatures,and design of a new inlet system [J].Atmospheric Measurement Techniques,9(7):2977-2988
Ku B K,Mora J F D L.2009.Relation between electrical mobility,mass,and size for nanodrops 1～6.5 nm in diameter in air [J].Aerosol Science and Technology,43(3):241-249
Li Z,Wang H.2003.Drag force,diffusion coefficient,and electric mobility of small particles.I.Theory applicable to the free-molecule regime[J].Physical Review E,68(6):061206
Pui D Y H,Romay-Novas F,Liu B Y H.1987.Experimental study of particle deposition in bends of circular cross section [J].Aerosol Science and Technology,7(3):301-315
Tammet H.1995.Size and mobility of nanometer particles,clusters and ions [J].Journal of Aerosol Science,26(3):459-475
Tammet H.2012.The function-updated millikan model:a tool for nanometer particle size-mobility conversions [J].Aerosol Science and Technology,46(10):i-iv
Ude S,Mora J F D L.2005.Molecular monodisperse mobility and mass standards from electrosprays of tetra-alkyl ammonium halides [J].Journal of Aerosol Science,36(10):1224-1237
Wang H.2010.Transport properties of small spherical particles [J].Annals of the New York Academy of Sciences,1161(1):484-493
Wang J,Flagan R C,2002.Seinfeld J H.Diffusional losses in particle sampling systems containing bends and elbows [J].Journal of Aerosol Science,33:843-857
Wilson S R,Liu Y,Matida E A,et al.2011.Aerosol deposition measurements as a function of reynolds number for turbulent flow in a ninety-degree pipe bend [J].Aerosol Science and Technology,45(3):364-375
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