THE MEASUREMENT OF THE FRACTAL DIMENSION OF INDIVIDUAL IN-SITU SOOT AGGLOMERATES USING A MODIFIED MILLIKAN CELL TECHNIQUE

A method is presented, using a modified Millikan cell, to measure the fractal dimension (D) of in situ carbonaceous agglomerates in three di mensional space. From the measured aerodynamic diameter (sedimentation technique) and the mass of the agglomerate (photoelectric technique), D of an individual agglomerate is derived. Results, in the range of 1 .87 less-than-or-equal-to D less-than-or-equal-to 2.19, were in good a greement with those of several theories and calibration against polyvi nyltoluene spheres which gave 2.96 less-than-or-equal-to D less-than-o r-equal-to 2.99. Agglomerate re-structuring by the electric field was observed and deliberately induced in two agglomerates to give D = 2.11 and 2.19. This mechanism was deduced to be responsible for the high v alues observed in D.