Hydroxyl and its concentration profile in methane–air flames

Abstract

Hydroxyl concentration profiles are measured in several atmospheric-pressure premixed laminar flames. The first quantitative comparison of hydroxyl concentration profiles to recent flame models is presented. These models include the influence of hydroxyl on fuel breakdown, on carbon monoxide oxidation, and on other species concentrations. The hydroxyl concentration profiles are measured by laser-induced fluorescence, and absolute mole fraction concentrations are determined by normalizing to laser absorption measurements in similar flames. The 100-microm spatial resolution of laser-induced fluorescence provides the first optical measurements of the flame's reaction zone at atmospheric pressure. The data are consistent with the electronic-excited state of hydroxyl having a negligible influence on the flame's structure.