Fundamental flame characteristics derived from counterflow flames are routinely used in chemical kinetic model optimization and validation. This paper reports an experimental and computational investigation aimed at understanding and quantifying the source of uncertainties associated with such characterizations using low extinction strain rate methane-air flames and high-extinction strain rate ethylene-air flames. In the experiments, two sets of convergent nozzles with exit diameters of 8mm and 14.7mm were used to inject non-premixed fuel and air to establish a planar flame in the counterflow mixing region. Velocity profiles and extinction data were measured using an LDV setup. Experiments were conducted at various separation distances for each set of nozzles to investigate potential differences in axial velocity profiles along the axial and radial directions and the corresponding local extinction strain rates. The slope of axial velocity in the axial and radial directions at the air outlet boundary was found to increase with decreasing separation distance. The variation of local extinction strain rate with changes in separation distance was within the uncertainty of experimental data. Both quasi one-dimensional and two-dimensional computations, using the most recent kinetic models, have been initiated to quantify the flow field effects identified in the experiments on the extinction strain rate of counterflow flames.
展开▼
