Estimation of Radiative and Scattering Characteristics of Sodium Aerosols Using Inverse Analysis

研究了钠火产生的气溶胶复折射率的估算方法。本文采用非灰色辐射传输分析方法，模拟了考虑多次散射的复折射率给定值时，均匀分散气溶胶层的辐射传输特性。采用蒙特卡罗方法进行分析，利用该程序得到了黑体炉对面墙面上大范围复折射率范围内气溶胶透过率的多组等高线。该透过率是由黑体炉发射的辐射得到的。通过将实验得到的透过率与分析得到的透过率等值线进行比较，估算出气溶胶的复折射率。利用已知光谱复折射率的氧化镁气溶胶进行了气溶胶透过率的实验。气溶胶是通过点燃镁带产生的，并由气流输送到矩形截面的管道中。用放大倍数为3000倍的显微镜测量了产生的气溶胶的粒度分布。气溶胶的质量浓度是通过称量设置在管道末端的纸过滤器来测量的。用黑体炉对面的辐射计测量了流经管道的气溶胶层的辐射透过率，将实验结果与分析得到的等高线曲线进行了对比，得到了准确的氧化镁复折射率。结果表明，用该方法可以估算出气溶胶的复折射率。

Estimation method is studied for complex index of refraction of aerosol generated by sodium fire. In the present study, non-gray radiative transfer analysis is carried out to simulate the radiative transmission through uniformly distributed dispersed aerosol layer for given values of complex index of refraction considering multiple scattering. The Monte Carlo method is used for the analysis.Using the program, several sets of contour curves of the transmittance of aerosol layer are obtained at several positions on the wall situated opposite to the black body furnace for a wide range of complex index of refraction of the aerosol. The transmittance is obtained for the radiation emitted from a black body furnace. The complex index of refraction of the aerosol is estimated by comparing the value of the transmittance obtained by experiment with the contour curves of transmittance obtained by analysis.The experiment to obtain transmittance of aerosol layer is carried out using magnesium oxide aerosol, whose spectral complex index of refraction is well known. The aerosol is generated by igniting magnesium ribbon, and is fed by air flow to duct with a rectangular cross section. The particle size distribution of the generated aerosol is measured by a microscope with a magnifying power of 3000. The mass concentration of the aerosol is measured by weighting the paper filter set at the end of the duct. Radiative transmittance of the aerosol layer flowing through the duct is measured using a radiation meter set opposite to a black body furnace.From the comparison of the results of the experiment and the contour curves by analysis, the complex index of refraction of magnesium oxide is estimated with good accuracy. From the result, it is concluded that the value of complex index of refraction of aerosol can be estimated by the present method.