Hydroxyl time-scale measurements in turbulent counter-flow flames

Time-series measurements of OH concentrations were obtained for a set of turbulent counter-flow nonpremixed H₂/CH₄/air flames. The normalized PSD collapsed at lower frequencies, which dominated the integral time scale, but displayed residual variations at higher frequencies. The near complete collapse of the two-time statistics indicated that the integral time scale is a good representation of hydroxyl fluctuations in these counter-flow nonpremixed flames. The integral time scale depended on the combined Re and strain rate (SR) approximately as Re-L35 in counter-flow nonpremixed flames. Time-series measurements of OH concentrations were also obtained for a set of turbulent counter-flow partially premixed CH₄/air flames. The effect of variations in Reynolds number and equivalence ratio on the fluctuation statistics was studied. This is an abstract of a paper presented at the 30th International Symposium on combustion (Chicago, IL 7/25-30/2004).