Asymptotic and Numerical Analysis of a Premixed Laminar Nitrogen Dioxide-Hydrogen Flame.
Asymptotic and Numerical Analysis of a Premixed Laminar
Nitrogen Dioxide-Hydrogen Flame.
Linteris, G. T.; Williams, F. A.
Combustion Science and Technology, Vol. 105, No. 4-6,
Sponsor:National Science Foundation, Washington, DC
premixed flames; laminar flames; nitrogen dioxide;
hydrogen; burning rate; flame structure
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 are
compared with the results using the reduced mechanisms,
and the sources of inaccuracies are identified. The two
reactions NO2 + H -> NO + OH and H2 + OH <- -> H2O + H
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 2 OH <- -> H2O +
O and NO2 + O -> NO + O2 are important for OH and O,
while the reactions NO2 + M -> NO + O + M and NO2 + H2
-> HONO + H serve as important initiation reactions.
The reactions O2 + H <- -> OH + O, H2 + O <- -> OH + H,
and 2NO2 -> 2NO + O2 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. Despite these limitations, an asymptotic
description of the flame structure using a one-step
approximation to the kinetics is still able to predict
the burning rate within a factor of three of the
numerical result using the full mechanism.