Coagulation dynamics of fractal-like soot aggregates

摘要: Abstract How the self-preserving distribution for soot aggregate size evolves as aerosol passes through transition regime from free molecule to diffusion limited collision dynamics is experimentally studied over range of fractal dimension 1.9 ⩽ D f 2.5 . To isolate coagulation nucleation and surface growth processes that normally coexist in flame, a premixed ethylene flame rapidly sampled cooled, introduced into residence time flow tube. At set distances downstream (corresponding 0.5–20 s) particles are again sampled, diluted, their recorded using differential mobility analyzer (DMA). These measurements show quickly established, but its shape varies function equivalence ratio height which sampled. A kinetic model based on Smoluchowski equation, employing kernels modified describe motion fractal-like regime, reproduces very well both shapes temporal evolution distributions. The indicates decreases = ∼ near front relatively lean flames ( Φ 2.0 ) more conventional value heavier sooting 2.4 Thermal desorption experiments effective density suggest these trends arise decrease semivolatile content present