AN EXPERIMENTAL-STUDY IN NON-PREMIXED FLAMES OF HYDROCARBON GROWTH-PROCESSES THAT INVOLVE 5-MEMBERED CARBON RINGS

Centerline profiles of temperature, soot volume fraction, and hydrocar bon concentrations were measured in a methane/air co-flowing non-premi xed dame whose fuel was doped with cyclopentane, cyclopentene, 1-methy lcyclopentene, and indene. Soot volume fraction and aromatic species c oncentrations were significantly increased by the additives, indicatin g that the presence of C5 ring-containing compounds in fuels has signi ficant implications for formation of soot and aromatic air toxics in c ombustion devices. Consideration of the order of the increases indicat es that they are attributable to direct chemical conversion of the add itives to aromatic species. Cyclopentene is most likely converted to b enzene by dehydrogenation to cyclopentadienyl, reaction of the cyclope ntadienyl with methyl radical to form methylcyclopentadienyl, and dehy drogenation/isomerization of the methylcyclopentadienyl to benzene. Me thylcyclopentene is most likely converted to methylcyclopentadiene by dehydrogenation, followed by the same dehydrogenation/isomerization pr ocesses, providing an even more efficient route to benzene. Indene und ergoes an analogous methyl addition process to form naphthalene.