Measurement of Soot with Organic Coatings by Laser-Induced Incandescence

HUGO A.R. TJONG (1), Steven Rogak (1)

(1) The University of British Columbia

     Abstract Number: 575
     Last modified: May 13, 2010

Abstract
Laser Induced Incandescence (LII) is a sensitive technique for the measurement of strongly absorbing aerosols (e.g. soot). Low-fluence, time-resolved LII uses 2-color pyrometry to measure the temperature after laser heating and can be used to infer soot primary particle size from the cooling curve. Presently, LII measurements are interpreted using heat transfer models without any consideration of coatings. If LII is to be used for atmospheric particles, it is important to understand the effects of liquid coatings on the particle energy balance. Furthermore, coatings can promote the collapse of aggregates, which also affects radiative and conductive heat transfer. Laboratory experiments show that LII can successfully detect the morphology changes due to coatings, but the apparent mass concentration decreases with coatings under some circumstances. A new model for heat and mass transfer during LII is presented to explain these effects. A coating compensation technique for future LII systems is proposed.