Electrostatic spraying of liquids in cone-jet mode

Abstract

Electrostatic spraying from a capillary is investigated in the case in which the droplets are formed by the breakup of a permanent jet extending from a volume of liquid in conical form. Domains of operation in this cone-jet mode have been determined after achieving good reproducibility of phenomena, which requires the effective control of multiple parameters. For a liquid of given conductivity, the jet diameter varies with the volume flow rate and the applied voltage, but only within a limited range whose extent depends in particular on the geometry of the capillary. Jet diameter and drop emission frequency measurements show that the energy minimization principle cannot be applied to this type of atomization; the ratio of the drop charge to Rayleigh limit charge varies greatly, depending on conditions. Several methods are indicated for reducing the droplet size differences, which are particularly noticeable when kink instabilities occur. © 1989.