Abstract A Fast Exhaust Nephelometer (FEN) is developed for light scattering measurement of particles produced by unsteady combustion processes, such as in diesel engines. The FEN simultaneously measures the light scattering intensity at three angles to infer the mass concentration (Cm), the geometric mass mean mobility diameter (dm,g), and the geometric standard deviation (σm,g) of polydisperse soot. A kernel is used to determine Cm, dm,g, and σm,g based on lookup tables generated with the Rayleigh-Debye-Gans light scattering model for fractal aggregates (RDGFA); the model incorporates the variation of the primary particle size (dp) with aggregate size (da), and nine parameters related to the soot properties, and one to the FEN optics. These parameters are determined a priori from literature and Transmission Electron Microscopy (TEM). The inverted Cm and dm,g are within ±10% of the gravimetric mass concentration and SMPS mobility diameter. This, however, largely depends on the choice of the parameters used to generate the lookup tables. A parametric study shows the inferred mass is most sensitive to uncertainties in the soot refractive index, the primary particle size, and the fractal pre-factor kf. Considering the wide range of soot refractive indices in the literature and the sensitivity of the morphological parameters to the processing of soot images, the uncertainty in mass concentration would be over 40%. Because of this, a novel approach of relating the size of primary particles to the size of aggregates is incorporated for the first time in the light scattering model, and reduces the uncertainty to ±25–30%. Copyright © 2020 American Association for Aerosol Research

中文翻译：

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用于快速发动机碳烟质量和尺寸测量的多角度光散射方法的开发和验证

摘要 开发了一种快速排气浊度计 (FEN)，用于对不稳定燃烧过程（例如柴油发动机）产生的颗粒进行光散射测量。FEN 同时测量三个角度的光散射强度，以推断多分散碳烟的质量浓度 (Cm)、几何质量平均迁移率直径 (dm,g) 和几何标准偏差 (σm,g)。核用于根据分形聚集体的瑞利-德拜-甘斯光散射模型 (RDGFA) 生成的查找表来确定 Cm、dm,g 和 σm,g；该模型结合了初级粒径 (dp) 与聚集体尺寸 (da) 的变化，以及九个与烟尘特性相关的参数，以及一个与 FEN 光学元件相关的参数。这些参数是从文献和透射电子显微镜 (TEM) 中先验确定的。倒置的 Cm 和 dm,g 在重量质量浓度和 SMPS 迁移率直径的 ±10% 以内。然而，这在很大程度上取决于用于生成查找表的参数的选择。一项参数研究表明，推断的质量对烟灰折射率、初级粒径和分形预因子 kf 的不确定性最为敏感。考虑到文献中烟尘折射率的广泛范围以及形态参数对烟尘图像处理的敏感性，质量浓度的不确定性将超过 40%。因此，光散射模型中首次采用了一种将初级粒子的大小与聚集体的大小相关联的新方法，并将不确定性降低到 ±25–30%。版权所有 © 2020 美国气溶胶研究协会