Electrons and the emission of soot from flames

Abstract

AN increasing body of evidence suggests that soot formation is associated with ionisation in flames and may be controlled electrically. Work in which sooting flames are subjected to large electric fields^1–3 shows that all soot particles are charged (at least in the presence of an applied field) and can therefore be manipulated by fields. This applies not only to fully formed particles but also to their growth and burning up in flames. Thus by applying fields so as to remove particles rapidly from the zone in which they are formed, their size as well as the total yield is greatly reduced. The former is ascribed to the decreasing residence times and the latter to the removal of surface on which growth can occur. Conversely, very large particles can be produced by holding them stationary against the gas flow by means of a field and thereby increasing their residence times. Also, any appreciable field intensity removes the charged nuclei on which carbon particles tend to grow³.