Benene formation chemistry in premixed 1,3-butadiene flames

Abstract

Premixed laminar 1,3-butadiene flames have been studied using detailed kinetic modeling. The results obtained have been compared against molecular beam mass spectrometry (MBMS) data obtained by Cole and co-workers in stoichiometric (=1.0) and rich (=2.4) near-sooting flames. Predictions of burning velocities and concentrations of major species and key radicals are satisfactory with agreement close to experimental uncertainties. Particular attention has been given to the formation of the first aromatic ring with alternative benzene formation paths discussed in the context of an extensive sensitivity analysis. The kinetic model also contains a comprehensive benzene oxidation mechanism, which has been independently validated in previous work. The developed mechanism accurately predicts benzene levels and the near 100-fold increase in benzene concentrations due to the change in stoichiometry. The present study thus extends past work on benzene formation in flames to include a C4 fuel. Butadiene flames are particularly interesting in this aspect since they provide an early branching among the C2, C3, and C4 chains. The results obtained show that several benzene formation paths are of importance. Thus, given experimental and modeling uncertainties, propargyl radical recombination, vinyl radical addition to 1,3-butadiene, and vinyl radical addition to vinyl acetylene must be considered. Furthermore, acetylene addition to 1,3-C4H5 becomes more competitive in the stoichiometric flame.