AROMATIC AND LINEAR HYDROCARBON CONCENTRATION MEASUREMENTS IN A NON-PREMIXED FLAME

Temperature and the concentrations of several major species, twenty on e hydrocarbon intermediates ranging in size from C2H2 to C12H10, and s oot were measured in an axisymmetric, atmospheric-pressure, laminar, c oflowing methane/air non-premixed flame. Gas samples were extracted fr om the flame with a quartz microprobe and analyzed on-line with single -photon photoionization mass spectrometry. Horizontal profiles were ob tained with millimeter spatial resolution at six heights above the bur ner surface that spanned the soot-containing portion of the flame. The flame contained numerous acetylenic species, benzene, many substitute d benzenes, and several two or three-ring compounds at concentrations exceeding one part per-million. The most abundant intermediate hydroca rbons were acetylene, then allene and/or propyne and benzene. The maxi mum concentrations of most linear hydrocarbons stayed roughly constant at different heights, whereas polyacetylenes and aromatics accumulate d with increasing height, with larger or more substituted aromatics pe aking higher in the flame. At the lowest height where methane was unde tectable, soot and all other hydrocarbons were also undetectable.