Simultaneous laser-induced fluorescence and Rayleigh scattering measurements of structure in partially premixed flames

Laser-induced fluorescence and Rayleigh scattering measurements were made i n well-stabilized, laminar partially premixed Bunsen-type methane/air flame s. Simultaneous Rayleigh scattering (temperature) and laser-induced fluores cence (flame radical concentration) enable precise determination of the pos ition of CH and OH radical structures in the gradient of the flame temperat ure. The OH and CH structures in the straight walls of the premixed inner f lame cone are well described by models incorporating detailed flame chemist ry and one-dimensional transport. Near the tip of the inner cone in regions of increased flame stretch, at richer stoichiometries of the premixed port ion of the flames, and in flames perturbed by a metal insert, the measured structure of CH and OH deviates from this simple description. CH concentrat ions predicted by the model depend on flow rate, thus suggesting the import ance of strain rate to prompt NOx formation in these flames.