Laser-Induced Incandescence (LII) is used in this study to measure the soot volume fraction for steady and unsteady laminar ethylene diffusion flames. For the steady flame the soot profiles obtained in this study using LII showed good agreement with those obtained previously using scattering/extinction technique. For the unsteady or flickering flames, we generated very repeatable time-varying diffusion flames by forcing the fuel flow at frequencies between 1-10 Hz. Phase lock images of the soot volume fractions were obtained for different phases between 0° and 360°. The sequential images showed the dynamics of the interactions between the generated vortices in the fuel and the flame. The phase-locked soot images revealed the entire motion process of the soot field during each pulsation period. The results obtained in the course of this study show that the soot emission decreased by lowering the oscillation frequency of the flame.
