RECIPES FOR USE OF EHD SPRAYING IN CONE-JET MODE AND NOTES ON CORONA DISCHARGE EFFECTS

The study concerns EHD spraying in cone-jet mode in air with a positive capillary. A modification of the tip of the capillary is described, making it possible in particular to regularize the breakup of the jet by electrical disturbances to produce fine droplets of approximately uniform size. Several sources of negative ions can be used to neutralize at least partially the droplets and obtain free aerosols. Corona discharge onset conditions are discussed, comparing the corona onset fields on metallic wires with the Rayleigh critical fields on liquid jets. Experiments conducted with a device similar to the ''Delft aerosol generator'' of Meesters et al. show that the spraying regime obtained by these authors is the classical cone-jet mode and the average droplet size is larger than indicated by their measurements.