2-DIMENSIONAL IMAGING OF SOOT VOLUME FRACTION BY THE USE OF LASER-INDUCED INCANDESCENCE

A recently developed laser-induced incandescence technique is used to make novel planar measurements of soot volume fraction within turbulen t diffusion flames and droplet flames. The two-dimensional imaging tec hnique is developed and assessed by systematic experiments in a coannu lar laminar diffusion flame, in which the soot characteristics have be en well established. With a single point calibration procedure, agreem ent to within 10% was found between the values of soot volume fraction measured by this technique and those determined by conventional laser scattering-extinction methods in the flame. As a demonstration of the wide range of applicability of the technique, soot volume fraction im ages are also obtained from both turbulent ethene diffusion flames and from a freely falling droplet flame that burns the mixture of 75% ben zene and 25% methanol. For the turbulent diffusion flames, approximate ly an 80% reduction in soot volume fraction was found when the Reynold s number of the fuel jet increased from 4000 to 8000. In the droplet f lame case, the distribution of soot field was found to be similar to t hat observed in coannular laminar diffusion flames. (C) 1995 Optical S ociety of America