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 positiv e 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 u niform size. Several sources of negative ions can be used to neutraliz e at least partially the droplets and obtain free aerosols. Corona dis charge onset conditions are discussed, comparing the corona onset fiel ds on metallic wires with the Rayleigh critical fields on liquid jets. Experiments conducted with a device similar to the ''Delft aerosol ge nerator'' 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.