Experimental and numerical investigations of the relation between OH* emission, flame speed and mass consumption rate

We investigate the relation between the intensity of the luminous emission of the excited OH* radical and the mass consumption rate of lean planar premixed methane-air flames. The flames were maintained perfectly flat using parametric acoustic stabilization in an imposed acoustic field. The consumption rate of the flames was varied by changing both the equivalence ratio and the temperature of the unburned mixture. We also compare our experimental measurements to the results of numerical simulations, using detailed chemical kinetics. For lean flames, we find that the OH* emission intensity is linear with mass consumption rate but, not proportional. Consequently, the relative fluctuation in mass consumption rate is not linearly related to the relative fluctuation in OH* emission intensity.