The index of refraction (IOR) is required to model thermal radiation interaction with pulverized solid fuels. In this work, the complex index of refraction of biomass (walnut shell) is therefore determined using pulverized particles. Single particles are irradiated, and the scattered radiation is measured in different directions. To avoid falsification of the scattering pattern (phase function), the particles are kept contactless in an acoustic levitator. Here, over 1000 different phase functions are measured. The measured scattering patterns are evaluated using an inverse evaluation procedure to determine the IOR. Mie theory serves as the basis for the mathematical modeling of the radiation properties of the particles. The measured IOR is then compared to data from the literature on coal. For the wavelength range λ=2000–4000nm no distinct differences are noticed between the coal and biomass IOR. For λ>4000nm the real part of the biomass IOR is larger and the differences increase with increasing wavelength. However, the order of magnitude still matches that of coal IOR, and thus, only minor differences in the radiative properties of coal and biomass are expected.

中文翻译：

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核桃壳颗粒光学性质的实验测定


折射率 （IOR） 是模拟热辐射与粉碎固体燃料相互作用所必需的。因此，在这项工作中，使用粉碎颗粒确定生物质（核桃壳）的复折射率。对单个粒子进行照射，并在不同方向测量散射辐射。为避免散射模式（相位函数）的伪造，颗粒在声悬浮器中保持非接触式。在这里，测量了 1000 多种不同的相位函数。使用逆向评估程序评估测量的散射模式以确定 IOR。Mie 理论是粒子辐射特性数学建模的基础。然后将测得的 IOR 与煤炭文献中的数据进行比较。对于波长范围 λ=2000–4000nm，煤和生物质 IOR 之间没有明显差异。对于 λ>4000nm，生物量 IOR 的实部更大，并且差异随着波长的增加而增加。然而，数量级仍然与煤 IOR 相匹配，因此，预计煤和生物质的辐射特性只有微小的差异。