Detailed structure study of a low pressure, stoichiometric H2/N2O/Ar flame

Abstract

A combined experimental and detailed chemical modeling study has been performed on a 20 torr, stoichiometric H2/N2O/Ar burner stabilized flame. Species concentration profiles were measured using molecular beam sampling with mass spectrometric detection and laser-induced fluorescence, while temperature profiles were measured with coated thermocouples. The burned gases of the flame contain about 2 mol.% of NO and H2, a concentration of approximately ten times more than that of their equilibrium. This formation prevents full energy release of the system within or near the flame zone. Experimental flame profiles of the major species, H2, N2O, N2, and H2O, as well as the minor species, NO, O2, OH, H, O, and NH, are presented and compared to calculated profiles generated by PREMIX, a one-dimensional premixed laminar flame code. The chemical mechanism used in the flame code was derived from a critical literature review and consists of 38 reactions and 14 species. Rate and sensitivity analyses performed reveal the intricacies of the mechanism as well as reactions important in the modeling of the experimental results. Several key reactions, including N2O + OH = HO2 + N2 and N2O + H = NO + NH, whose rate coefficients have been controversial, are discussed in detail. In addition, the importance of various collision partners in the key initiation step, N2O + M = N2 + O + M, is presented and discussed.