DETERMINATION OF ABSOLUTE METHYL-RADICAL AND HYDROXYL-RADICAL CONCENTRATIONS IN A LOW-PRESSURE METHANE OXYGEN FLAME

An experimental and theoretical investigation of OH- and CH3-radical p rofiles in a premixed stoichiometric CH4/O2 flat flame burning at a to tal pressure of 10 Torr has been carried out. Relative OH concentratio n profiles were determined using laser-induced fluorescence (LIF). Abs olute calibration of these relative profiles was performed using absor ption spectroscopy giving a mole fraction of about 5% OH in the burnt gas region. Absolute CH3 concentrations were obtained from in situ abs orption measurements. A maximum CH3 mole fraction of 1.2% was determin ed. The experimental data are in reasonable agreement with the results of flame structure calculations.