Dataset to "Experimental determination of the optical properties of walnut shell particles"

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 lambda = 2000 - 4000 nm no distinct differences are noticed between the coal and biomass IOR. For lambda > 4000 nm 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.

折射率（index of refraction, IOR）是模拟热辐射与粉状固体燃料相互作用的必要参数。本研究中，研究人员通过粉状颗粒测定生物质（核桃壳）的复折射率（complex index of refraction）。对单个颗粒施加辐照，并在多个方向上测量其散射辐射。为避免散射模式（相函数，phase function）出现失真，颗粒通过声悬浮装置实现无接触悬浮。本研究共测得超过1000组不同的相函数。通过逆向评估流程对测得的散射模式进行分析，以确定复折射率。米氏理论（Mie theory）作为颗粒辐射特性数学建模的理论基础。随后将测得的生物质复折射率与文献中煤炭的折射率数据进行对比。在波长范围2000~4000 nm内，煤炭与生物质的折射率未出现显著差异。当波长大于4000 nm时，生物质折射率的实部更大，且差异随波长增加而逐步扩大。但二者的数量级仍与煤炭折射率保持一致，因此预计煤炭与生物质的辐射特性仅存在微小差异。