Soot particle size distribution measurements in laminar diffusion flames of n-heptane with oxygenated aromatic fuel additives by time-resolved laser-induced incandescence

Soot particle size profiles of a laminar co-flow diffusion flame were determined using time-resolved laser-induced incandescence (TiRe-LII) for various fuels. In the fuel matrix, both the level (0-20 vol %) and type (oxygenated versus non-oxygenated) of aromaticity was varied. Motivation for this study was earlier engine research, which demonstrated that the addition of certain aromatic oxygenates, among which anisole and veratrole, to diesel fuel manifested in lower engine out particle emissions. The co-flow burner research conducted in this study may conclude that the presence of oxygenated aromatics, although less detrimental than the non-oxygenated variety, toluene, still manifested in both greater soot volume fractions and particle sizes than was the case for the aliphatic base fuel, n-heptane. Hereby, the effectiveness of aromatic ring oxygenation was most pronounced for the first functional oxygen group. The addition of a second functional oxygen had little impact on the results.