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Annals of the Assembly for International Heat Transfer Conference 13

ISBN 1-56700-225-0 / CD 1-56700-226-9

Volumes per year:

various

Year 2006

DOI: 10.1615/IHTC13.p26

MASS SPECTROMETRIC, LASER-INDUCED FLUORESCENCE AND CHEMICAL KINETIC MODELING STUDIES OF N₂O AND NO₂, BURNER-STABILIZED FLAMES

R. Sausa
US Army Research Laboratory, Aberdeen, MD 21005, USA

D. Venizelos
Zeeco Incorporated, Broken Arrow, OK 74014, USA

J. Cabalo
US Army Edgewood Chemical Biological Center, Edgewood, MD 21010, USA

ABSTRACT

We report on our experimental and chemical modeling studies of H₂/N₂O, H₂/NH₃/N₂O, and H₂/N₂O/NO₂ flames. We studied these flames in order to test and refine a detailed chemical mechanism that we assembled from critical literature review. Our mechanism consists of over 100 reactions and 22 species. We measured the flame temperatures with a coated, thin-wire thermocouple, and by OH and NH laser-induced fluorescence (LIF). A multiparameter, computer program based on a Boltzmann, rotational distribution analyses yields the flame temperatures as a function of height above the burner. The program utilizes OH and NH rotational energy levels and one-photon line strengths, and its parameters include laser line shape, temperature, and absolute and relative frequency values of the observed spectral data. We measured the flame species concentrations of H₂, NH₃, NO₂, N₂O, N₂, H₂O, NO, O₂, NH and OH by molecular beam-mass spectrometry, LIF, or both, and also calculated them with PREMIX, a one-dimensional, laminar, flame code, with our detailed chemical mechanism as input. Overall, the PREMIX calculations predict very well the major and minor species concentrations throughout each flame. The addition of about 4% of NH₃ to the H₂/N₂O flame decreases the post flame O₂, OH, and NO concentrations by approximately 90, 45, and 35%, respectively. This decrease is predicted rather well by the PREMIX calculations, which show a decrease in O₂, OH, and NO by approximately 90, 55, and 40%, respectively. The shapes of the modeled O₂, NO, and OH profiles for the H₂/N₂O/NO₂ flame are also in good agreement with those observed experimentally. The modeled OH profile even predicts an observed peak at approximately 3.5 mm above the burner surface. Our rate and sensitivity analyses reveals that this OH peak is due to the competition between the NO₂+H = NO+OH reaction, which produces OH, and the H₂+OH = H₂O+H reaction, which consumes it.