Statistical analyses of quasiclassical trajectory data for air dissociation

A large database of quasiclassical trajectory (QCT) results, sampled from Boltzmann distributions, is analyzed in aggregate. N₂ +N₂, N₂ +N, N₂ +O₂, O₂ +O₂, and O₂ +O interactions are considered for a temperature range of 4000 K to 30,000 K, including equilibrium and nonequilibrium test sets. For all of these reactions, the mechanics of dissociation are studied and found to be similar. The effect of collision partner internal energy on dissociation is found to be likely negligible. Vibration has a more pronounced effect on dissociation than rotation, which is found to be due to rotation increasing the centrifugal barrier. A variety of chemical kinetics models for CFD from the literature are also compared to the present data. The classic Marrone-Treanor [1] preferential dissociation model is found to accurately describe all data in the nonequilibrium test sets, but it neglects the effect of rotational energy on dissociation. A modified model is proposed that describes rates to within 22% and vibrational energy changes due to dissociation to within 4% of the dissociation energy. These data, insight about dissociation, and model findings should enable more accurate modeling of chemical kinetics for CFD.