Numerical and Experimental Studies of Hydroxyl Radical Chemiluminescence in Methane-Air Flames

Abstract

A numerical and experimental study of hydroxyl radical chemiluminescence from methane-air flames was performed. Measurements of the chemiluminescence per unit flame area for lean methane-air flames were obtained, and a model for use in predicting chemiluminescence was developed. The model was one-dimensional and unsteady, incorporating the equations of species continuity and energy, with temperature- and concentration-dependent transport and thermodynamic properties. The reaction mechanism included the chemiluminescent reaction, as well as reactions that both produced and quenched electronically excited OH. It was found, both experimentally and numerically, that the chemiluminescent intensity was highly dependent on the equivalence ratio. For !he range of equivalence ratios studied experimentally (0·65 < φ < 0·90) there was an exponential dependence of chemiluminescence on equivalence ratio. The predicted chemiluminescent intensity was most sensitive to the rate constant of the reaction, , in both lean and rich flames. The model is able to predict both the total hydroxyl radical chemiluminesnce from a steady flame, and the time-dependent chemiluminescence from melhane-air mixtures in a shock tube.