The charging and mobility of chain aggregate smoke particles

Abstract

The fluid drag force and unipolar diffusion charge on chain aggregate smoke particles produced by an exploding wire and from a hydrocarbon flame were studied with a system consisting of an electrical particle counter (EPC) and classifier and a condensation nuclei counter (CNC) From measurements of particle electric mobility, electric charge, and numbers of primary particles per aggregate the fluid drag as a function of equivalent spherical diameter was measured and compared with three different theories.It was found that for aggregates consisting of from 10 to 300 primary particles having a mass mean diameter on the order of 0.05μ, the fluid drag was nearly the same as that of a sphere having a volume equivalent to that of the aggregate. The diffusion charge was found to be about 70% higher than that of the equivalent sphere.The theory and data suggest that the relative independence of fluid drag and shape for this size aggregate is due to the opposite effects of increased surface area and gaseous slip.