Neutralization of an electrospray by a corona discharge

Abstract

A numerical analysis is presented of the neutralization of a dilute electrospray by a corona discharge of polarity opposite to that of the spray droplets in the gap between two parallel disks charged to different electric potentials. An Eulerian description of the spray is combined with a transport equation for the corona ions and mass and momentum conservation equations for the gas. Two configurations of the corona are considered. In one of them the corona is generated outside of the gap and the corona ions are injected through an orifice opposite to the inlet orifice of the spray. The corona current that can be injected by these means is limited by the space charge of the ions already present in the gap. The maximum corona current increases with the voltage applied between the disks, and the minimum voltage required to achieve full neutralization increases with the flow rate of the electrospray. In the other configuration the corona is generated around a point electrode on the axis of the spray. The ionic current is not limited in this case. However, partially discharged droplets are attracted to the point electrode and deposit on it if neutralization is not completed before the droplets reach the electrode.