Chemical Kinetic Modeling and Mass Spectrometric and Laser-Induced Fluorescence Measurements of NH(3)/N(2)O Flames

摘要

Experimental and chemical modeling studies of a 60 Torr, NH3/N2O/Ar flame are performed in order to provide further testing and refinements of a detailed chemical mechanism developed previously in our laboratory. This mechanism, which is denoted as VS, consists of 87 reactions and 20 species. Flame temperatures are measured with a coated thin-wire thermocouple and by rotational analyses of OH and NH laser-induced fluorescence (LIF) spectra. Species concentration profiles of NH3, N2O, N2, H2O, NO, O2, NH, O, and OH are recorded using molecular beam-mass spectrometry, LIF, or both. The experimental species concentrations are compared to those obtained with both equilibrium and PREMIX flame code calculations. The NH3/N2O mixture equilibrium calculations agree very well with both the PREMIX and measured postflame N2 and H2O concentrations but underpredict the postflame NO concentration and overpredict the O2 concentration. The PREMIX calculations predict very well the shapes of the experimental NH3, N2O, N2, H2O, NO, OH, and NH profiles throughout the flame but do not adequately predict the shape of the O-atom profile and overpredict the O2 concentration by 60% at 16.25 mm, suggesting that the VS mechanism requires some refinement. A VS modified mechanism, which provides better agreement with the experimental results, is proposed. In this mechanism, the rate constants of the following reactions are altered to the limit of their experimental or calculated uncertainties: (1) N2O + H = OH + N2, (2) NH2 + O = HNO + H, (3) NH2 + OH = NH + HO, (4) NH + H = H + NH, (5) NH3 + OH = NH2 + H2O, and (6) NO + H + M = HNO + M.