The effects of equivalence ratio on the formation of polycyclic aromatic hydrocarbons and soot in premixed ethane flames

Abstract

The formation of polycyclic aromatic hydrocarbons (PAH) and soot has been investigated in atmospheric-pressure, laminar, ethane/oxygen/argon premixed flames as a function of mixture equivalence ratio. Mole fraction profiles of major products, trace aromatics, substituted aromatics, and PAH were quantified by direct gas chromatography/mass spectrometry (GC/MS). Soot particle diameters, number densities, and volume fractions was determined using static (classical) light scattering. The dependencies of flame species mole fraction profiles on equivalence ratio, using the expression, X i max = A i φ n i were also determined. The parameter n i , an indication of sensitivity to equivalence ratio, for stable aromatic precursors exhibits the following rank order: c-C 5H 6 (4.21) > C 3H 4 (3.09) > b-C 4H 6 (2.43) > C 4H 4 (2.20) > C 4H 2 (2.16) > C 2H 2 (1.66). For aromatic species, the values of n i were in the following order: phenylacetylene (9.33) > benzene (8.17) > indene (7.97) > toluene (6.39). In comparison, PAH species were extremely sensitive to flame equivalence ratios, with the following n values: benzo[a]pyrene (30.37) > acenaphthylene (15.33) > cyclopenta (cd) pyrene (14.58) > fluoranthene (13.52) > pyrene (12.73) > anthracene (11.18) > phenanthrene (10.79) > naphthalene (8.99).