Experimental and numerical study of soot formation and evolution in co-flow laminar partially premixed flames

The changing of particle features throughout the flame, evidenced by the variation in thermal emissivity, was further investigated using Raman spectroscopy. The analysis of Raman spectra showed that the increase in thermal emissivity follows a reduction in the hydrogen-to-carbon ratio of the investigated soot nanoparticles. Measurements performed with the TPD method also evidence that both particle emissivity and volume fraction are strongly affected by oxidation, which prevents to accurately measure soot concentration in oxidative regions of the flames. An attempt to include soot oxidation in the TPD method for a correct evaluation of volume fraction procedure is also illustrated. OH concentration profiles, obtained from a modeling analysis and validated by radical chemiluminescence measurements, were used in the TPD method to correct particle concentration due to oxidation.