Charalampopoulos T T, Hahn D W, Chang H
Appl Opt. 1992 Oct 20;31(30):6519-28. doi: 10.1364/AO.31.006519.
The scattering and extinction behavior of multicomponent particles formed in flame systems is significant in a number of research areas and practical applications, such as the production of superconducting and other ceramic materials by means of the aerosol route as well as pollutant suppression through the use of metal additives. The objective of this study is to assess the role of iron pentacarbonyl vapor addition on the light scattering and extinction behavior of flame soot. Calculations were carried out by using the scattering models for homogeneous and coated spheres and comparisons were made between the particle diameters and volume fractions. In addition, scattering, absorption, and dynamic light-scattering measurements at the wavelength of 488 nm in a premixed propane-oxygen flame with a fuel-equivalence ratio of ? = 2.4 unseeded and seeded with iron pentacarbonyl vapor 0.32% by weight iron to fuel were performed. The refractive index and number densities of the soot particles in the unseeded flame we determined as functions of position above the burner by combining the scattering and absorption measurements with the particle size-distribution parameters determined from photocorrelation. In the seeded flames the soot particles were found to contain iron oxide throughout the flame. Thus the data were analyzed by using both the scattering-absorption model for coated spheres and the Maxwell-Garnett relation for the effective refractive index. Differences up to 131% in particle-volume fractions were found from the data analysis by using the constant and variable effective index of the mixture (soot plus iron oxide). The results of the coated-sphere analysis are discussed and the effects of particle agglomeration on the inference of particle-volume fractions are assessed. It is concluded that the effects of particle optical inhomogeneity in the analysis of scattering and absorption data from multicomponent particles cannot be neglected.
火焰系统中形成的多组分颗粒的散射和消光行为在许多研究领域和实际应用中都具有重要意义，例如通过气溶胶途径生产超导和其他陶瓷材料，以及使用金属添加剂抑制污染物。本研究的目的是评估五羰基铁蒸气的添加对火焰烟灰光散射和消光行为的作用。使用均质球体和包覆球体的散射模型进行计算，并对粒径和体积分数进行比较。此外，在燃料当量比φ = 2.4的预混丙烷 - 氧气火焰中，分别在未添加以及添加0.32%（重量比，铁/燃料）五羰基铁蒸气的情况下，于488 nm波长处进行了散射、吸收和动态光散射测量。通过将散射和吸收测量结果与由光相关法确定的粒度分布参数相结合，确定了未添加火焰中烟灰颗粒的折射率和数密度随燃烧器上方位置的变化关系。在添加了五羰基铁蒸气的火焰中，发现整个火焰中的烟灰颗粒都含有氧化铁。因此，使用包覆球体的散射 - 吸收模型和有效折射率的麦克斯韦 - 加尼特关系对数据进行了分析。通过使用混合物（烟灰加氧化铁）的恒定和可变有效折射率进行数据分析，发现颗粒体积分数的差异高达131%。讨论了包覆球体分析的结果，并评估了颗粒团聚对颗粒体积分数推断的影响。得出结论，在分析多组分颗粒的散射和吸收数据时，颗粒光学不均匀性的影响不可忽略。
