Understanding and predicting the temporal response of laser-induced incandescence from carbonaceous particles

摘要: This paper describes a model for analyzing and predicting the temporal behavior of laser-induced incandescence (LII) from combustion-generated soot, carbon black, other carbonaceous particles on nanosecond time scale. The accounts particle heating by absorption light pulsed laser cooling sublimation, conduction, radiation. also includes mechanisms oxidation, melting, annealing nonthermal photodesorption clusters surface. At fluences above 0.1 J/cm2, temperatures during pulse are determined balance between whereas at lower do not reach sublimation temperature, predominantly controlled conduction. After pulse, conductive rates. Oxidative may compete with these scales. Annealing to more ordered phase is predicted occur as low 0.02 J/cm2. strongly influence rates, changes in emissivity increase signal decay Supersonic expansion sublimed surface calculated 0.12 J/cm2. When compared LII measurements recorded flame atmospheric pressure, reproduces shapes relative magnitudes profiles over wide range fluences. Comparisons predictions experimental observations suggest that melt lead melting bulk graphite. These comparisons indicate energy released much smaller than neutron- or electron-irradiated Despite good agreement results, large uncertainties exist input parameters used calculate rates absorption, emission, photolytic desorption both initial annealed particles.