Application of two-photon laser-induced fluorescence for visualization of water vapor in combustion environments.

Investigations concerning the potential for the visualization of water vapor in combustion processes have been made. The water molecules were excited through a two-photon excitation process at 248 nm with a tunable excimer laser; this was followed by fluorescence detection between ~ 400 and 500 nm. In the experimental work special care was taken to map the possible spectral interferences from hot O(2), which also absorbs in the same spectral region and which produces fluorescence emission that interferes with the water fluorescence. Experimental investigations of high-pressure applications are also presented.

Finally, two-dimensional (2-D) measurements made at room temperature, taken in an atmosphericpressure flame, and taken in an engine simulator at elevated pressure are presented. These results indicate that the detection limit for 2-D single-shot registrations under optimized experimental conditions was estimated to 0.2% at atmospheric pressure and at room temperature. Extrapolations to flame conditions are also presented.