Formation and dispersion of small water droplets in an insulating oil under a pulsed electric field

The water droplet formation and motion in a viscous mineral oil was studied in the presence of a pulsed high voltage electric field (150 Hz, peak voltage up to 18.4 kV). Experiments were carried out in an inclined (angles: 3-90 degrees) rectangular cell (38×10×10 cm), equipped with parallel electrode plates along two sides of the cell. As the applied peak voltage was increased, the formed droplets were reduced in size and showed repulsion and some upward scattering; the droplet velocity near the nozzle was significantly increased by the pulse electric field, with the droplets decelerating as they moved away from the nozzle. It was observed from experiments that three modes of droplet formation from single charged nozzle could be defined based on applied peak voltages (Vp): (1) single-droplet-regime (Vp<6 kV); (2) transient-regime (6p<12 kV); (3) multi-droplet-regime (12p<18.4 kV).