Quantitative hydroxyl concentration time-series measurements in turbulent nonpremixed flames

Quantitative hydroxyl concentration time-series measurements have been obta ined by picosecond time-resolved laser-induced fluorescence in a series of methane-air and hydrogen-argon-air nonpremixed flames. The recovery of a qu antitative time series is complicated by the need to account for fluctuatio ns in the fluorescence lifetime. We have recently developed instrumentation that enables the simultaneous measurement of fluorescence signal and lifet ime. The present research represents the first application of this techniqu e to turbulent Barnes. The correction for hydroxyl lifetime fluctuations is shown to be significant for mean concentrations and thus probability densi ty functions but negligible for power spectral densities (PSD's). The hydro xyl PSD's were found to vary slightly with radial and axial location in the flames and to vary significantly with Reynolds number. However, the PSD's in the H-2-Ar-air flames are nearly identical to those in the CH4-air flame s. (C) 1999 Optical Society of America.