High pressure studies of propene combustion

Oxidation of propene, an important stable intermediate formed in the combustion of C₃ and larger hydrocarbons and oxygenated biofuels, was studied in both a high pressure laminar flow reactor at ~800 K and in high pressure rich and lean premixed laminar flames. These experimental platforms provide insight to propene oxidation kinetics for a broad range of temperature and fuel loading conditions at high pressure, where few experimental data are available. Such high pressure conditions shift the chemistry to regimes of higher kinetic uncertainty and sensitivity. Lean premixed laminar burning rates measured up to 20 atm in a nearly constant pressure chamber agree with model predictions, though model predictions are significantly slower for rich conditions. Rich flame predictions are particularly sensitive to reactions of the fuel and its fragments that control the radical pool, such as CH₃+H(+M)=CH₄(+M), C₃H₆+H=aC₃H₅+H₂, aC₃H₄+H=aC₃H₅, and reactions of other C₁ and C₂ fragments. Flow reactor measurements at 15 atm and ~800 K reveal slow reaction with none observed at 770 K, both observations being in contrast with predictions using models found in the literature. Predictions of flow reactor species evolution profiles are sensitive to initiation reactions involving long-lived resonantly-stable allyl (aC₃H5) radical selfrecombination. Inclusion of this reaction submodel greatly increases predicted induction time and improves model predictions of species gradients.