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Abstract
Planar oxygen-enhanced methane counterflow flames are investigated by optical diagnostics and numerical simulation. The major species concentrations and temperature measured from Raman scattering are compared to the detailed simulations of the flame formed between two opposed jets. The effect of stretch and the influence of oxygen concentration in the oxidizer on the flame structure are studied for nitrogen-diluted methane fuel (20% CH4 in N2). The oxygen concentration of reactants changes the flame temperature dramatically. Simulations with the GRI-3.0 and the San Diego chemical kinetic mechanisms show that model-data comparisons for reactants, products such as H2O, and temperature agree very well. The measured CO2 is in agreement at lower oxygen enrichment (≤40% O2) but deviates from prediction at high oxygen enrichment (60%, 100% O2). The effect of the fuel concentration in the nitrogen-diluted fuel is also studied for pure oxygen flames. When pure oxygen is the oxidizer, the measured extinction limit for the minimum amount of fuel in the diluted fuel mixture is very close to the calculated result when using either the GRI-3.0 or the San Diego chemical kinetic mechanisms. At low-level enrichment (i.e., 30% O2) and high-level enrichment (100% O2), the GRI-3.0 and the San Diego mechanisms give almost identical predicted results.
Acknowledgments
This research work was partially supported by Gas Research Institute. Air Products and Chemical, Inc provided most of the gases used in this research. The authors give special thanks for this support.
