Simultaneous temperature and multi-species measurement in a lifted hydrogen diffusion flame by a KrF excimer laser

Abstract

An ultraviolet spontaneous vibrational Raman scattering technique has been developed and applied to a lifted hydrogen jet diffusion flame. Simultaneous, temporally and spatially resolved point measurements of temperature, major species concentrations (H{sub 2}, O{sub 2}, N{sub 2}, H{sub 2}O), and absolute hydroxyl radical concentration (OH) are obtained with a single excimer laser for the first time. For OH measurement, the use of laser-induced predissociative fluorescence makes quenching corrections unnecessary. In the center core of the lifted flame base, fuel and oxidizer are rich, premixed, and unignited. Combustion occurs in an intermittent annular turbulent flame brush with strong finite-rate chemistry effects. The OH radical exists in subequilibrium and superequilibrium concentrations. Major species and temperature are found with nonequilibrium values. Further downstream the superequilibrium OH radicals decay toward equilibrium through slow three-body recombination reactions. 32 refs.