Corona discharge in electrospraying

• The spectroscopic analysis of electric discharge in electrospraying has been carried out.
• Spectroscopic measurements shown that electric discharge is inherent to electrospraying.
• Glow discharge stabilizes cone-jet mode via stabilizing the electric field at the nozzle outlet.

The paper presents investigations of current–voltage and light emission characteristics of electrospraying of various liquids in atmospheric air. The spectroscopic measurements have shown that the onset of corona discharge coincides with the onset of electrospraying, with the voltage increasing. The emission intensity in selected spectral lines during electrospraying depends on spraying mode, discharge power and a kind of liquid. In the specific experimental conditions in air, mainly the N2 second positive system, which is visible as violet faint light, has been recorded. The emission intensity of other gaseous species, which could be product of electrosprayed molecules decomposition or dissociation, was at very low level for the voltages applied, i.e., for glow or onset streamer discharges. From the measured light emission spectra of discharges from capillary nozzle and liquid jet, the dependence of the amplitude of selected spectral lines on capillary-nozzle voltage has been determined and it was found that this relation can be approximated by a third-degree polynomial function. This approximation has been supported by theoretical considerations. The presented results support the hypothesis that faint electrical discharges (glow, onset streamers) usually occur during and are inherent to electrospraying.