Structure and size of soot nanoparticles in laminar premixed flames at different equivalence ratios

Our results evidence that the particle size distribution is strongly affected by the flame equivalence ratio. Slightly rich flames produce mono-modal PSD with very small particles of only few nanometers. Bi-modal size distribution are found in richer flames when larger particles, i.e., 5-20 nm, are formed. Change from a mono-modal to a bi-modal particle size distribution can be related to changes in particle graphitization as evidenced by a slight increase of the in plane average size of the polyaromatic units within the particles, La, and a change in particle optical properties.