Recent studies have highlighted the need for additional fundamental flame data, at turbine relevant conditions, to better constrain the chemical kinetics of hydrogen oxidation. This paper studies the effect of ambient pressure on the extinction limits of non-premixed hydrogen flames. Experiments were performed in the counterflow configuration between 1 and 7 atm. Experimental results were simulated using a number of recent chemical kinetic reaction models for hydrogen oxidation. Measured extinction limits demonstrate both a positive and negative ambient pressure dependency. Accurate modeling of this characteristic shift from positive to negative pressure dependence relies primarily on a number of factors. First, an accurate representation of the transition from a system dominated by the branching H + O_2 → O + OH to that dominated by the termination, H + O_2 + M → HO_2 + M reaction. Secondly, it relies on an accurate parameterization of the rate for the reaction HO_2 + OH → H_2O + O_2.
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