Characterization of young soot from an inverse diffusion flame

Investigations have been completed to characterize young soot formation in an inverse diffusion flame (IDF) with ethylene fuel. Several different measurements have been taken to provide information regarding young soot characteristics. Scanning mobility particle sizer measurements determined the size distribution of soot both at the flame exhaust and near the base of the flame. Thermophoretic particle densitometry was performed to determine the temperature and soot volume fraction throughout the flame. TEM and High Resolution-TEM images were also performed to observe the morphology of the soot and confirm the SMPS findings. Filter samples, photoacoustic analysis (PA), and elemental and organic carbon (EC/OC) measurements have also been taken. These results were compared with the same measurements taken from the exhaust of a fuel rich, premixed ethylene flame. The IDF had a much higher percent extractable than the premixed flame, and GC analysis on the extractable portion showed smaller compounds than those found in traditional soot. The feature of the young soots of interest is that the absorption coefficient obtained by the PA is almost a factor of 2 lower in the IDF, as compared with a premixed flame exhaust, as would be expected for a soot with a less developed structure and a higher H/C ratio.