Experimental approaches of laser-induced incandescence technique for soot measurement

The laser-induced incandescence (LII) technique has emerged as a viable non-intrusive technique for measuring soot concentration in flames. The incandescence of soot occurs when laser light heats the particles to the incandescent temperature (which is typically /spl sim/4,000 K). It has been shown that the resulting radiant emission intensity is proportional to the soot concentration. Studies compared the LII intensities to light extinction measurements of soot volume fraction to show this proportionality relationship. There are many practical benefits for using LII for soot concentration measurements. This technique is more accurate than the conventional light extinction method because it is expected to be less sensitive to light scattering by soot particles and absorption by large PAH molecules. With proper calibration, the LII technique is believed to be ideal for use in flames producing large gradients in soot concentrations (for which the light extinction-deconvolution may not be suitable) and for turbulent flames that do not possess symmetric characteristics.