Charge to radius dependency for conductive particles charged by induction

Abstract

Particle charge is a critical parameter that needs to be determined in order to accurately predict behavior of a charged particle exposed to electrical forces. The effectiveness of various electrostatic applications depends directly on this charge or, more specifically, the charge to mass ratio. Previous studies report conflicting data for the size dependency of charge. In this paper, the relation between the value of charge on a conductive particle and the particle radius in the process of induction charging is investigated. The results of numerical simulations of a liquid atomization process are presented and a novel approach to the analytical solution of the problem is introduced. It is found that the exponent in the particle charge to radius dependency is equal to two when the particle is in the direct contact with the bulk material. The radius exponent decreases rapidly as the atomizing ligament length is increased. For ligament lengths many times greater than the particle radius, the radius exponent approaches one. Agreement between numerical and analytical results is found to be very good. The results of this study clarify some of the conflicting data in the previously published literature and suggest that the particle charge is practically linearly dependent on radius for atomized liquid particles and proportional to particle surface area for solid particles. In addition it is shown that the charge to mass ratio for liquid particles can be maximized by ensuring the ligament length during atomization is maximum.