Cylindrical conductive particles in the proximity of an electrode affected by a high-intensity electric field

The electrostatics of cylindrical conductive particles between parallel plane electrodes is a research topic related to the development of various technologies which make use of electric fields for processing of granular materials. A program based on the boundary-element method was employed in order to compute the charge acquired by conductive cylinders and the force acting on them, while in contact with or in the proximity of an electrode, affected by a uniform field. The calculations shown that the field intensification generated by these particles is a function of their charge, of their dimensions and of their position with respect to an electrode of similar or opposite polarity. The basic experimental set-up consisted of two horizontally disposed parallel-plate electrodes, in air at atmospheric pressure. In some experiments, the upper electrode was substituted by a matrix of corona-emitting points, in order to evidence the peculiarities of particle behaviour in an ionized field. Conductive cylinders (diameters: 0.5-1.5 mm, lengths: 2-20 mm) were placed on the bottom electrode. The dielectric strength of air gaps containing single conductive particles was found to decrease in the presence of space charge. Mobile cylindrical particles were proved to be more harmful than the fixed ones.