Jennifer Herdman - Raman signatures and laser-induced incandescence with direct numerical simulation of soot growth in non-premixed ethylene/air flames

Version 1

      Publication Details (including relevant citation   information):

      Citation: Carbon 2011,   49, 5298-5311.

      Co-Authors:

      Blair C. Connelly

      Mitchell D. Smooke

      Marshall B. Long

      J. Houston Miller

      Institutions:

      Department of Chemistry, The George Washington University,   Washington, DC 20052, USA

      Department of Mechanical Engineering, Yale University, New Haven,   CT 06520-8284, USA

      Abstract:

      The predictions of “soot” concentrations from numerical   simulations for nitrogen-diluted, ethylene/air flames are   compared with laser-induced incandescence and Raman spectra   observed from samples thermophoretically extracted using a rapid   insertion technique. In some flame regions, the Raman spectra   were obscured by intense, radiation that appeared to peak in the   near infrared spectral region. There is a good agreement between   spatial profiles of this ex situ laser-induced incandescence   (ES-LII) and the “traditional” in situ laser-induced   incandescence (IS-LII). Raman signatures were observed from low   in the flame and extended into the upper flame regions. The   spectra consisted of overlapping bands between 1000 and 2000   cm-1 dominated by the “G” band, near 1580   cm-1, and the “D” band in the upper 1300   cm-1 range. Several routines are explored to   deconvolve the data including 3- and 5-band models, as well as a   2-band Breit–Wigner–Fano (BWF) model. Because the Raman signals   were observed at heights below those where in situ-LII was   observed, we postulate that these signals may be attributable to   smaller particles. The results suggest that the observed Raman   signals are attributable to particulate with modest   (approximately 1 nm) crystallite sizes. This observation is   discussed in the context of current models for nascent particle   formation.

      Address (URL): http://www.sciencedirect.com/science/article/pii/S000862231100618X