Three-angle scattering/extinction versus TEM measurements on soot in premixed ethylene/air flame

In this work, a three-angle scattering and extinction technique has been applied in order to study soot formation and growth in a rich ethylene/air premixed flame (Φ=2.34). The Rayleigh–Debye–Gans theory together with the fractal-like approach has been applied to derive soot parameters, in terms of volume concentration and morphology. A mathematical procedure is presented to obtain the radius of gyration by considering scattering signals collected at two supplementary angles. TEM measurements, carried out at different locations on the flame axis, are used to derive some parameters, such as fractal prefactor, fractal dimension and size distribution, to be entered in the mathematical treatment of optical data. The radius of gyration and the primary particle size as obtained by TEM and by optical measurements are compared. Good agreement has been found in the upper part of the flame investigated. Discrepancies observed low in the flame are discussed.