Optical sizing of aggregated combustion particles: computational development of a two-angle laser scattering technique

To simplify the experimental efforts involved in the nonintrusive optical characterization of typical combustion-generated particulates, an inverse analysis of scattering measurements at only two angles is developed and evaluated based on the exact scattering computations on simulated fractallike aggregates. Two optimum angles are suggested by combination of theoretical (sensitivity analysis) and practical (spatial resolution) considerations that have led to the interpretation of spherule diameter from the ratio of large-angle scattering and absorption coefficients and the aggregate gyration radius from the ratio of scattering dissymmetry. The inferred spherule and aggregate sizes are found to be generally in good agreement with the initially prescribed values for the range of physical and optical particulate properties considered here. These computational results under precise simulation conditions demonstrate the accuracy of the proposed particulate-sizing technique by avoiding the common experimental uncertainties that prevent a definitive performance assessment of any experimental method.