The blowout limit of a jet diffusion flame in a coflowing stream of lean gaseous fuel-air mixtures

The blowout limit of a circular jet diffusion flame in a low velocity coflowing stream of air is extended significantly by the introduction of a small amount of some fuel vapor in a surrounding flow. The jet fuels employed were methane or hydrogen, while the coflowing stream contained, in turn, methane, hydrogen, propane, or ethylene. The widening of the flame blowout limit could be correlated to the concentration of the fuel in the surrounding stream relative to the corresponding concentration that caused a flame flashback within the surrounding stream in the presence of the jet flame.Moreover, the blowout limit of the flame of a jet of methane containing significant proportions of a diluent such as nitrogen was also extended markedly by the presence of fuel in the surrounding stream. As expected, when carbon dioxide was the diluent in the central jet instead of nitrogen, relatively higher fuel concentrations were needed in the coflowing stream to provide the same jet blowout velocities.