Size distribution and morphology of nascent sootin premixed ethylene flames with and withoutbenzene doping

摘要

Particle size distribution functions of nascent soot formed in four burner-stabilized, premixed ethylene–oxygen–argon flames were studied in a spatially resolved manner by online sampling/scanning mobilityparticle sizer. Particle morphology was analyzed by atomic force microscopy (AFM) of substrate-depositedsamples. Two of the four flames were doped with benzene. An aerosol electrometer is introduced to extendthe lower detection limit to around 1.5 nm in diameter. The results show that the bimodal behavior of particlesize is applicable to all premixed ethylene flames studied. The variation of the size distribution fromflame to flame is conclusively attributed to flame temperature variation. Under the condition of an equalcarbon concentration, benzene doping leads to negligible changes in the characteristics of the size distribution.For all flames studied, AFM observations show that nascent soot is liquid-like and spreads extensivelyupon impact on a substrate surface.