Soot Formation and Oxidation in Unsteady Spray Flame via Laser-Induced Incandescence and Scattering Techniques.

Two kinds of planar soot imaging techniques, laser-induced incandescence (LII) and laser-induced scattering (LIS) techniques, were applied simultaneously to an unsteady free spray flame achieved in a rapid compression machine. An analysis of LII and LIS images yielded three qualitative images of soot concentration, size of soot particles, and number density of soot in the flame. These images revealed that the soot is formed mainly in the center region of a flame, resulting in an appearance of a soot cloud with high number density and small particle size in this region. The soot size increases and the number density decreases when soot is conveyed downstream.