The quantitative characterization of sooting flames in terms of soot load a
nd total soot surface area continues to be a major challenge in both fundam
ental investigations and practical applications. More particularly, a major
interest can be found to discriminate the two classes of particulate, name
ly soot and cenosphere, presents in power generation plants fuelled with he
avy fuel oils.
The Laser-Induced Incandescence (LII) technique is widely employed for the
determination of soot volume fraction but LII may also be used to derive th
e particle diameter, profiting from the size-dependent cooling behavior of
the laser-heated particles. The temporally resolved LII emissions has been
successfully used in a heavy fuel oil spray flame to distinguish the two cl
asses of carbonaceous particles produced during the heavy fuel oil combusti
on. Moreover, it has been possible to follow along the flame axis the forma
tion and burn-out of these two classes of particulate and their relative am
ount in terms of volume fraction.