Regular Article
Generation of Monodisperse Water Droplets from Electrosprays in a Corona-Assisted Cone-Jet Mode

https://doi.org/10.1006/jcis.1995.1464Get rights and content
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Abstract

An experimental investigation was performed on water electrosprays operated in the cone-jet mode. Because of the high surface tension of water, the establishment of stable sprays in air is generally prevented by the occurrence of electric breakdown in the gaseous environment surrounding the spray and its destabilizing consequences on the spray behavior. When air is replaced with CO2, a gas with higher breakdown threshold, operation in the cone-jet mode is possible, as first demonstrated by the pioneering work of Zeleny. Under these conditions, two well-distinguished stability domains were found in the plane of operating variables, voltage vs liquid flow rate, both domains being characterized by a stable cone-jet mode of operation. One of them pertains to the "classic" cone-jet mode. The other is here named the corona-assisted cone-jet mode , since the characteristic cone-jet morphology is accompanied by a steady corona discharge. Evidence of gas-phase ionization was found directly by interfacing the electrospray to a mass spectrometer. The presence of the discharge is indispensable to the establishment of this novel mode, since replacement of CO2 with SF6, a gas with even higher breakdown threshold, destabilized the spray. This new domain of spray operation has the important consequence of decreasing by more than one order of magnitude the minimum flow rate and, consequently, the minimum droplet size that can be electrosprayed, which results in the production of monodisperse water droplets with diameters anywhere from about 10 μm down to the submicrometer range.

Keywords

electrospray
corona
monodisperse
droplet
electrostatic
spray

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