Electrohydrodynamic atomisation of water stabilised by glow discharge—operating range and droplet properties

Abstract

This paper deals with the production of charged water droplets by electrohydrodynamic atomisation (EHDA) of water, in air at atmospheric pressure, in a mode stabilised by a particular corona discharge regime. Indeed, impulse filamentary discharges developing in the gas around the liquid cone temporarily disrupt the EHD equilibrium leading to an unstable mode of EHDA with varying droplet properties (size and charge). The purpose of this paper is to show that a stable mode can be obtained by the control of the field divergence around the liquid, i.e. the electric field profile in the gas, leading to a continuous glow discharge without impulse filamentary discharge. Using observations, electrical measurements and droplets size characterisation, several spraying modes are depicted. We have demonstrated that the electrical discharge regime (continuous/impulse) induces the mode of EHDA (stable/unstable). The stability domains are defined versus liquid flow rate, conductivity, voltage for different nozzle diameters. Then, the properties of droplets (droplets diameter, spray current) produced within these modes are established as a function of the liquid flow rate, of the conductivity and of the glow current.