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 profiles in a premixed stoichiometric CH4/O2 flat flame burning at a total pressure of 10 Torr has been carried out. Relative OH concentration profiles were determined using laser-induced fluorescence (LIF). Absolute calibration of these relative profiles was performed using absorption spectroscopy giving a mole fraction of about 5% OH in the burnt gas region. Absolute CH3 concentrations were obtained from in situ absorption measurements. A maximum CH3 mole fraction of 1.2% was determined. The experimental data are in reasonable agreement with the results of flame structure calculations.