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。本研究采用非灰色辐射传输分析方法，模拟了在复折射率给定值下，考虑多重散射的均匀分布分散气溶胶层的辐射传输。采用蒙特卡罗方法进行分析。利用该程序，得到了在黑体炉对面壁面不同位置上气溶胶层透射率的几组轮廓曲线，适用于较大范围的气溶胶复折射率。得到了黑体炉辐射的透射率。通过对比实验得到的透光率值与分析得到的透光率轮廓曲线，估算出气溶胶的复折射率。利用已知氧化镁气溶胶的光谱复折射率，进行了气溶胶层透射率的测定实验。气溶胶通过点燃镁带产生，并由气流送入矩形截面的管道。用放大倍数为3000的显微镜测量产生的气溶胶的粒径分布。气溶胶的质量浓度是通过对管道末端设置的纸过滤器称重来测量的。通过管道的气溶胶层的辐射透过率使用设置在黑体炉对面的辐射计来测量。将实验结果与分析得到的等高线曲线进行比较，得到氧化镁的复折射率，精度较高。结果表明，该方法可以估算气溶胶的复折射率。

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.