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Abstract
The Scattering by Two-Angle Ratio (STAR) light scattering method described in this article is based on a new analysis of a well-established theory in the literature that describes black carbon soot as fractal agglomerates. Previous analyses have shown that the measured scattering signals at two appropriate angles can be used to determine the mean agglomerate particle size and mass concentration. The current work shows that a dimensionless invariant function of the two-angle scattering ratio can be defined (Cm #), for computation of the mass concentration and mean agglomerate size. In addition, the three soot optical properties can be combined into one overall soot property constant, Sp , which, based on literature measurements of each component property, is also near invariant for a variety of fuel and combustor conditions. Research literature on optical parameters has been used (without resorting to arbitrary calibrations) to compute values of the gas phase soot mass concentration. In a companion article (Holve et al. Citation2011), measurements of diesel and gas turbine engines show that the model for interpreting scattering measurements from STAR is in reasonable agreement with gravimetric measurements.
Acknowledgments
This work was supported in part by the Navy and Air Force SBIR programs. Many thanks to Chris Sorensen for devoting time and effort on informative and spirited discussions, leading to a clearer understanding of PFA and RDG as applied to soot.