沙尘气溶胶粒子数量浓度计算及激光传输特性

Calculation for the number concentration of dust aerosol particles and characteristics of laser transmission

沙尘气溶胶粒子的数量浓度很难直接测量,但又是影响激光传输特性最主要的因素之一。基于沙尘气溶胶粒子的质量浓度,利用其粒径分布特性推导出了粒子数量浓度的计算公式。利用Mie理论和Monte Carlo方法研究了激光在沙尘条件下的传输特性,分析了激光的传输衰减和透射率随波长和质量浓度的变化关系,给出了能见度随粒子质量浓度的变化曲线,并对两种方法的计算结果进行了比较。结果表明:在选择的几个波长中,激光在波长为10.6μm时的传输衰减最小(仅为1.06μm时的58%左右),并且随着质量浓度的增加能见度先是迅速降低而后缓慢降低,其变化趋势接近双曲线。该方法基于粒子的质量浓度(可直接测量)计算沙尘气溶胶的激光传输特性,在实际应用中具有非常重要的理论意义。

The number concentration of dust one of the most important factors affecting aerosol particles is hard to be directly measured, but it is the laser transmission characteristics. Based on the mass concentration of dust aerosol particles, using the size distribution of particles, the formula for calculating the number concentration of particles was deduced. Under the condition of sand and dust, the transmission characteristics of laser was studied by using Mie theory and Monte Carlo method, the relationship of the transmission attenuation and transmittance with wavelength and the mass concentration were analyzed, curve of visibility along with particle mass concentration was given, and the calculation results of Mie theory and Monte Carlo method were compared. The results show that, in the choice of several wavelengths, the transmission attenuation is minimum when wavelength is 10.6 μm （about 58% of that in the 1.06 μm）, with the increase of mass concentration, the visibility decreased rapidly and then decreased slowly, whose trend is near hyperbolic curve （this parameter can be measured directly）, aerosol, which has very important theoretical The method, basing on the mass concentration of particles can calculate the laser transmission characteristics of dust significance in practical application.