Experimental study of electro-spraying modes of deionized water in atmospheric environment

The liquid emitting from capillary subjected to a high electric voltage could be dispersed in different ways depending on applied potential and flow rate. The electro-spraying of deionized water was experimentally studied adopting the high-speed camera under different operating parameters. The time resolved images and evolution of drop or/and jet initiation, pulsation, deformation, and separation from capillary tip or meniscus were captured and analyzed. The known electro-spraying modes were identified according to the geometrical forms of meniscus, jet, or/and drop. A spherical droplet with diameter larger than the outer diameter of capillary could be generated in dripping mode at low potential, while a spherical droplet with diameter smaller than outer diameter of capillary could be observed in micro-dripping mode with relative high potential. Spindle-like droplet could be found in spindle mode and usually further disperse into a few of drops with different size for larger flow rate. In the range of applied potential and flow rate, oscillating jet and simple jet could be found, where a long jet could be elongated by electric stresses and further break up into finer drops with highly charged drops. In addition, the operating parameters and drop sizes for different modes are also discussed. Meanwhile, the spraying modes with double capillaries were also observed and discussed.