Abstract

Laser-induced fluorescence measurements are made of hydrogen atoms, and of OH, CH and NO radicals in slightly rich methane/air flames burning at 30 and 70 Torr. Spatially resolved measurements above a flat flame burner provide relative concentration versus reaction time. Absolute NO and OH concentrations are determined through separate calibration experiments. Spatially resolved gas temperature is deduced from OH rotational excitation scans. Spatially resolved measurements above a flat flame burner provide relative concentration vs reaction time. Predicted profiles of the concentrations of these radical species as a function of height above the burner surface are obtained from a computer model of the flame, and are compared with experiment. Good agreement is obtained for relative concentration profiles for all species, for absolute NO concentration, and ratios at the two pressures. CH is the main precursor to NO; a slight disagreement between its computed and experimental profiles indicates some remaining unknown aspect of its high temperature chemistry.

© 1991 Optical Society of America