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

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      Publication Details (including relevant citation   information):

      Citation: Carbon 2011,   49, 5298-5311.


      Blair C. Connelly

      Mitchell D. Smooke

      Marshall B. Long

      J. Houston Miller


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

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


      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.

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