Focusing particles with diameters of 1 to 10 microns into beams at atmospheric pressure
Focusing particles with diameters of 1 to 10 microns into beams at atmospheric pressure
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DOI：
10.1080/02786820802360674
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发表时间：
2008-01-01
影响因子：
5.2
通讯作者：
Freedman, Andrew
中科院分区：
文献类型：
--
作者：
Deng, Rensheng;Zhang, Xuefeng;Freedman, Andrew
我们报告的环境压力空气动力学的透镜的颗粒在1-10 μ m的直径范围内，在约1升/分的流速下操作，大大增加了下游的透镜的颗粒数密度。该透镜的低压降（10-30 Torr）可最大限度地降低泵送要求，从而降低功耗。数值模拟表明，小孔粒子斯托克斯数和小孔直径与管径的比值是决定透镜性能的关键因素。气体雷诺数（在1000的数量级上，比气溶胶质谱仪中使用的典型透镜系统大两个数量级）对光束直径和颗粒传输效率两者仅具有微弱的影响。模型结果，验证光散射实验，表明，一个透镜与最终管内径为1.65毫米和一个单一的孔直径为0.75毫米，可以产生光束直径远小于0.10毫米。该系统的有效工作距离，类似于1厘米的孔下游，是有限的过渡到湍流的喷嘴下游。这也将透镜设计限制为单个孔。计算和测量的传输效率范围从小于3 μ m的颗粒的单位到10 μ m颗粒的40%。同时实现窄光束和优异的透射效率被限制在大约三倍的颗粒尺寸范围内，因此没有这种设计的单个透镜可以同时包含整个1-10 μ m的颗粒尺寸设计范围。
We report on an ambient-pressure aerodynamic lens for particles in the 1-10 mu m diameter range, operating at a flow rate of about 1 lpm, that greatly increases the particle number density downstream of the lens. Intended for use with optical monitors, the lens's low pressure drop (10-30 Torr) minimizes pumping requirements and thus power consumption. Numerical modeling indicates that the orifice particle Stokes number and the ratio of orifice diameter to tube diameter are the critical determinants of lens performance. The gas Reynolds number (on the order of 1000, two orders of magnitude greater than typical lens systems used in aerosol mass spectrometers) has only a weak effect on both beam diameter and particle transmission efficiency. Model results, validated by light scattering experiments, indicate that a lens with a final tube with inner diameter 1.65 mm and a single orifice of 0.75 mm diameter can produce beam diameters of far less than 0.10 mm. The effective working distance of the system, similar to 1 cm downstream of the orifice, is limited by transition to turbulence in the jet downstream of the orifice. This also limits the lens design to a single orifice. Calculated and measured transmission efficiencies range from unity for particles smaller than 3 mu m to similar to 40% for 10 mu m particles. Simultaneous achievement of both a narrow beam and excellent transmission efficiency is limited to about a three-fold range in particle size, so no single lens of this design can simultaneously encompass the entire 1-10 mu m particle size design range.