Laser-Induced Fluorescence, Mass Spectrometric, and Modeling Studies of Neat and NH3-Doped H2/N20/Ar Flames

A combined experimental and modeling study of neat and NH,-dopcd (cI> =. 1).30 Torr flames is reported. The major species concentrations are measured by molecular beam mass spectrometry (MB/MS), whereas the minor species OH. NH, and O-atom concentrations arc measured by laser-induced fluorescence (LIFT The species NO is measured hoth by LlF and MB/MS. and O2 by MB/MS. The flame temperatures are measured both by OH and NH LIF and by thin wire thermometry. The flames are modeled with PREMIX using the temperature profiles and several detailed chcmical mechanisms as input. The mechanisms include the G RI 2.11, SSLA, and their derivatives. The SSLA mechanism was developed previously in our laboratory from a critical literature review. Calculations using all the mechanisms predict fairly well the profiles of the major species for both neat and doped flames. Howevcr, both the SSLA and GRI 2.11 calculations fail to predict the postflamc O2 concentration in the neat flame. the drop in the O2 concentration with the addition of NH,. and the NH, dccay in the doped flame. Sensitivity analyses suggest refinements to the SSLA, and GRI 2.11 mechanisms. Thc experimental results arc predicted rather well lIsing a modified SSL4 mechanism in which the NH + NO = Nl) + H reaction rate is decreased and thc NzO + M N, + 0 + M reaction rate and/or H20 third body efficicncy is increased to the limit of their uncertainty. Rate analyses performed on the modeled calcUlations reveal the reactions importanl to NO, 02ʹ NH, OH. and O-atom production and consumption and NH, consumption. These reactions ;lrc presented and diswsscd.