EXPERIMENTAL ASSESSMENT OF NAPHTHALENE FORMATION MECHANISMS IN NON-PREMIXED FLAMES

Concentration profiles of stable hydrocarbons were measured along the centerline of several axisymmetric co-flowing methane/air non-premixed flames whose fuels were doped with 2500 to 1900 ppm of benzene, tolue ne, ethylbenzene, styrene, and phenylacetylene. The results indicate t hat the H-abstraction/C2H2-addition mechanism proposed by Frenklach an d co-workers was responsible for the naphthalene formed in the undoped , benzene-, styrene-, and phenylacetylene-doped flames. However, a sec ond source of naphthalene, possibly a reaction between benzyl and prop argyl radicals, was important in the toluene-and ethylbenzene-doped fl ames. Soot volume fractions were also measured in each flame; the maxi mum values correlated well with the maximum naphthalene concentrations , indicating that naphthalene formation is the critical soot formation step for these fuel mixtures containing one-ring compounds.