Asymptotic and Numerical Analysis of a Premixed Laminar Nitrogen Dioxide-Hydrogen Flame

Abstract

A kinetic mechanism of eighty-some reactions for flames in mixtures of hydrogen and nitrogen dioxide is systematically reduced to twenty-four-, eleven-, seven-, two-, and one-step mechanisms. The numerically predicted burning rates for the full mechanism describing a near-stoichiometric burner-stabilized flame at a pressure of 25 torr, and final temperature of 2000 K are compared with the results using the reduced mechanisms, and the sources of inaccuracies are identified. The two reactions account for about 97% of the NO₂ and H₂ consumption and NO and H₂O production, and are the principal reactions involving OH and H atoms. The reactions are important for OH and O, while the reactions serve as important initiation reactions. The reactions are significant but of lesser importance. In reducing the mechanism, the steady-state assumptions for the intermediates O, H. and OH are shown to be good; however, their use is limited because the H and OH balance relations are dominated by the same reactions. As a result of these limitations, an asymptotic description of the flame structure using a one-step approximation to the kinetics is only able to predict the burning rate within a factor of three of the numerical result using the full mechanism

Key Words:

• Reduced mechanisms
• laminar flames
• premixed flames
• flame chemistry

Additional information

Notes on contributors

F. A. WILLIAMS

Work supported by National Science Foundation under contract number CTS92-14888