Abstract View
Light Backscattering from Post-flame, Cooled Soot Particles
PRAKASH GAUTAM, Justin Maughan, Christopher Sorensen, Kansas State University
Abstract Number: 234
Working Group: Aerosol Physics
Abstract
We studied light scattering due to soot particles generated by ethylene, propane and oxygen combustion via a pre-mixed burner. The measurements were made at a wavelength of 532 nm with vertically polarized incident light in the scattering angle range from 0.32° to 157°. The scattering volume was in a post-flame region where the soot was nearly at room temperature. The results showed a fractal dimension of -2.00 ± 0.15 with an enhancement in the backscattering, a result not observed theoretically. For analysis, soot particles were collected from the scattering volume region using a thermophoretic sampling devices. The size distribution shown by transmission electron micrographs (TEM) was in good agreement with the size distribution given by an aerodynamic particle sizer (APS 3321) and consistent with Guinier analysis of the scattering. Further, the micrographs indicated that some soot particles were dense aggregates while others were ramified fractal aggregates. We propose that these represent water coated and dry aggregates, respectively. Based on our TEMs, we further propose that our experimentally observed backscattering is due to the dense aggregates which results from the presence of water in the soot aerosol.