Quantitative imaging of temperature and OH in turbulent diffusion flames by using a single laser source

Abstract

We describe a diagnostic technique for obtaining quantitative, simultaneous, and instantaneous images of temperature and the concentration of the hydroxyl radical OH in turbulent flames. The technique uses a single laser source and a single intensified CCD camera. A stoichiometric premixed flame is used for calibration. We use detailed calculations of laminar flames of similar fuels to estimate the effects of quenching and ground-state population on the OH signal. A factor combining both effects is generated as a function of temperature. We validate the technique by comparing measured temperature and OH number density with calculated values in laminar diffusion flames. Absolute errors of 10-20% and 20-30% are estimated on the measured temperature and OH number density, respectively. The technique is applicable to regions of the flames where the Rayleigh cross section is close to that of air.