Opposed jet flames of lean or rich premixed propane-air reactants versus hot products

Several opposed jet flames, produced by a lean H-2-air jet opposing a rich or lean C3H8-air jet, are investigated. Spontaneous Raman spectroscopy is used for major species concentration and temperature measurements along the opposed jet centerline. The hot products of the H.-air flame simulate the burnt gases of I impinge upon a weak-burning lean or rich hydrocarbon-strong-burning near-stoichiometric reactants as they fueled reactant mix, a situation encountered in stratified charge operation of direct injection spark ignition engines. In addition the H-2-air name hot products facilitate experimental data interpretation through the absence of carbon-bearing species. Good agreement between numerical and experimental data are obtained for a rich (equivalence ratio, (phi = 1.25) C3H8-air jet versus a lean (phi = 0.4) H-2-air jet. Two lean C3H8-air jets (0 = 0.64 or 0.60), versus the phi= 0.4 H-2-air jet, are also investigated. For both of those flames, the amount of Co-2 production strongly depends upon phi), with the 6 0.64 flame having a peak CO2 mole fraction an order of magnitude higher than for the (h = 0.60 flame, and the C3H8 flames burning either as a normal flame (high Co-2) or as a negative flame speed flame producing little CO2 and then only through diffusion of C3H8 into the hot products jet. The numerically predicted and experimental CO2 profiles agree well for the positive flame speed flame, but the large discrepancy between predicted and measured peak CO2 in the negative flame speed flame suggests modeling improvements Lire needed for this type of flame. (C) 2002 by The Combustion Institute.