Towards a quantitative understanding of the role of non-Boltzmann reactant distributions in low temperature oxidation

摘要: Abstract An essentially universal assumption of chemical kinetics is that bimolecular reactions only occur between reactants rovibrational energy described by a Boltzmann (thermal) distribution. Given the O 2 mole fraction roughly 20% under nearly all relevant low-temperature combustion situations, there significant potential for molecules to undergo reactive collisions with on same time scale as energy-transferring necessary achieving Within context combustion, this phenomenon conceivably gives rise an entirely non-Boltzmann sequence involving multiple fuel-derived radicals produce OH radicals. complex interplay among simultaneous internal isomerizations, collisions, dissociations and across reaction surfaces, estimating extent deviations from conventional thermal assumptions not straightforward. A novel methodology presented coupling master equations deriving effective phenomenological rate constants sets products in chemically activated sequences proceed surfaces. The used establish better understanding nature reactant distribution effects quantify their magnitude. As case study, we implement explore effect product branching fractions QOOH *  + O n -propyl oxidation well its associated dependence fraction, temperature, pressure. While it appears will be considerably smaller at higher pressures (at least propane), consideration likely required interpretations experimental measurements commonly investigate R + O QOOH + O central engine-relevant ignition behavior. With regard observable signatures these experiments, presence stronger-than-usual may indicator