Measurement and investigation on the deformation and air-assisted breakup of charged droplet

The present work concerns experimentally the deformation and breakup of charged droplet in the dripping mode. A high-speed camera combined with a microscopic zoom lens has been used to visualize the deformation and breakup morphology of charged droplet. Subsequently, a deformation rate which can describe the degree of deformation is used to study the effects of some parameters on charged droplet deformation. A home-made device has been designed and succeeds in calculating the tiny charge (nC) on a water droplet, and with the action of aerodynamic force the effect of charge on water droplet breakup is consequently obtained. The experiments show that at deformation stage the mediums with different conductivities will tend to have little effect on droplet deformation for the conductive liquids. Bigger surface tension produces a lower deformation rate and a higher voltage is needed to make the droplet change from the dripping mode to the cone–jet mode. Capillary diameter is also another key factor which influences the deformation rate, the deformation rate increases as the capillary diameter increases. Higher voltage implies a larger deformation rate for whatever mediums that have been tested. During the breakup stage the breakup time of charged droplets and the degree of bag elongation before breakup are all shorter than uncharged ones. Charged drop at low airflow velocity can gain quick breakup equal to uncharged drop of higher airflow velocity. That means breakup will be enhanced once droplets have been charged.

► We study experimentally the deformation and breakup of charged droplet in the dripping mode.
► A home-made measurement device succeeds in calculating the tiny charge (nC) on water droplet.
► Charged droplet deformation is related to the electric force, droplet diameter and physical properties.
► A charged drop at low airflow velocity can gain quick breakup equal to uncharged drop of higher airflow velocity.