Development of a technique for high-temperature chemical kinetics: Shock tube/pulsed laser-induced fluorescence imaging method

A technique for the measurements of high-temperature gas-phase chemical reactions, like those involved in combustion, has been developed and an application to OH-radical measurement has been evaluated. The developed method, shock tube/pulsed laser-induced fluorescence imaging technique, allows us to measure a quantitative concentration-time profile of radical species by a single laser pulse. The detection limit for OH radicals was as low as $1×1012moleculescm−3$ at total pressures (mainly argon) of $1.5–2.4bar$ and temperatures of $1300–1750K$⁠, when exciting the 1-0 band of the OH $A-X$ transition with $a∼1mJ$ laser pulse (full width at half maximum $0.15cm−1$⁠). The applicability to time-resolved chemical kinetic measurements has been investigated by measuring the rate constants for the reaction of OH radicals with benzene $(C6H6)$⁠. Because of the high detection sensitivity, the initial OH-radical concentration could be kept low enough, $∼1×1013moleculescm−1$⁠, to prevent the influence of side reactions. The measured rate constants agreed well with the previous reports and their extrapolation to higher temperatures. These results demonstrate the applicability of the technique to kinetic measurements for reactions of combustion interests.