The two-dimensional (2-D) OH concentration distribution in an axisymmetric coflow methaneair diffusion flame was measured by using planar laser-induced fluorescence (PLIF) technique. On the other hand, the flame structure was calculated numerically by using a detailed chemical reaction mechanism and the accurate thermal and transport properties. The adopted mechanism was GRI mechanism involving 49 species and 279 elementary reactions. The derived flame structure made it possible to obtain the 2-D distribution of the collisional quenching rate and thus to evaluate its effect on the OH fluorescence emission distribution. The evaluation has revealed that the effect is not appreciable and the PLIF method is a convenient and reliable technique to obtain the 2-D relative concentration distribution of OH.
