Optical and Probe Measurements of Soot in a Burning Fuel Droplet Stream

Publisher Website
Google Scholar
Abstract
Measurements have been made of the size, number density, and volume fraction of soot particulates present in a controlled spray flame. The flame was nearly one-dimensional, and resulted from the combustion of a continuous stream of fuel droplets of uniform initial size and spacing. Two independent techniques were applied simullancously to soot sampling. The first was an in-situ method in which particulate parameters were inferred from the polarization dependence of Mie scattered laser radiation at a fixed angle. The second approach relied on the use of an electrostatic sampling probe for soot collection and, then, an electron microscope for analysis of the soot morphology. The particulate parameters were determined at three burning times for the combustion of 300 urn diameter No. 2 fuel oil droplets. A comparison of the optical and probe results demonstrated quite good agreement between the two approaches; however, in making the comparison, due regard was given to the irregular chain-like structure of the particulates and the different sensitivities of the two methods to the nearly spheroidal components of the chain. The closest agreement was obtained for the volume fraction reflecting its relative insensi-tivity to particulate shape. The results suggest that chain-like agglomeration occurs in the flame and is not, therefore, solely a probe-induced effect.