Theory of diffusion charging of arbitrarily shaped conductive aerosol particles by unipolar ions

Abstract The theory of diffusion charging of aerosol particles by unipolar ions having no external electric fields, is re-examined for arbitrary particle shape. For smaller effective Knudsen number (continuum limit), the time history of the charging of arbitrarily shaped particles can be obtained when the capacitance of the particles is known. For larger effective Knudsen numbers, the time history of the charging of arbitrarily shaped particles can be obtained when the capacitance and surface area of particles are known. Systematical analyses have been presented for bipolar sphere, oblate and prolate spheroids. The effect of gravitational motion of large aerosol particles on the charging process has been discussed.