Classification of electrohydrodynamic spraying modes of water in air at atmospheric pressure

We report an experimental study of the electrohydrodynamic (EHD) spraying of water in air at atmospheric pressure. A ceramic capillary with an inner diameter of 20 μm was used as an EHD spray nozzle. We observed the structure of the meniscus and jet at flow rates in the range 0.1–4 ml/h using sub-nanosecond pulsed laser illumination, and identified three distinct regimes of EHD spraying based on the shape of the meniscus and motion of the jet; i.e., a straight jet, a transition regime, and a whipping jet regime. Based on these observations, we identified the stable operating regimes for EHD spraying.