CARS thermometry in fuel-rich combustion zones

Abstract

Experimental and theoretical investigations of N₂ coherent anti-Stokes Raman scattering (CARS) thermometry in laboratory ethylene–air diffusion flames have revealed significant nonresonant susceptibility effects in fuel-rich regions of the flames. The effects appear to be due to the size of the nonresonant susceptibility for typical hydrocarbon fuels and can give rise to significant temperature errors if not accounted for. An efficient theoretical algorithm for reducing spectra affected by nonresonant interference is presented and shown to give excellent agreement with experiment. It is shown that uncertainty about mixture composition or the values of nonresonant susceptibilities of individual constituents need not have a significant effect on CARS temperature measurement.