Experimental and numericla studies are made of H_2-N_2-air laminar counterflow diffusion flames strained by steadily impinging micro fuel jet or air jet from the fuel side for the air side. Direct observation and two-dimensional temperature measurements by laser Rayleigh scattering method show that th eflame strained by the micro fuel jet from the fuel side (flame 1) is easily quenched locally, but the flame strained from the air side (flame 2) hardly extinguishes and the flame temperature tends to increase. Numerical computations. taking into account detailed chemical kinetics and mutlicomponent diffusion. Predict well the characteristics of the experimental findings noted above for the strained flames 1 and 2. They reveal the factors dominating the flame characteristics; that is, (1) H_2 of the fuel component is diluted by nitrogen compared to the original fuel near the central axis at stoichiometric condition in flame 1 with micro fuel jet but is concentrated in flame 2 with micro air jet due to the preferential diffusion among species in lean and stoichiometric region due to the nonunity Lewise number effect. It is also noted that the maximum flame temperature camot be rationalized by the local stretch rate but changes widely depending on the flame configuration.
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