Measurements of temperature and OH radical concentration in combustion gases by absorption spectroscopy with a diode laser

In this study we demonstrate in-situ quantitative measurements of temperature and OH radical concentration profiles in a post-flame region between premixed twin flames, and thus show the potential for use of diode-laser absorption spectroscopy as a combustion diagnostic tool. The diode laser used in this study is an external cavity diode laser (NewFocus Model 6328) operating near 1.5 /spl mu/m. The laser frequency was modulated and slowly scanned across the absorption features simultaneously by applying a 1 kHz sinusoidal wave and a 0.15 Hz sawtoothed signal onto the voltage input of the piezoelectric transducer attached to the tuning mirror of the laser cavity.