Modeling trajectories of electrohydrodynamic atomization droplets in simple-jet mode: investigating impact of additional forces
Abstract
Electrohydrodynamic atomization, or Electrospraying, is a process of implementing electric
stresses into a liquid breakup process by the application of a strong electric field (kV cm-1).
For a certain spray geometric configuration and a specified liquid, there are different modes
of electrospraying depending on the electric field strength and/or liquid flowrate. The conejet
mode is the most explored one due to its capability of producing highly charged
monodisperse droplets in the nano-micrometer size range. This mode is, however, not
recommended for systems that depend on electrospray at high throughput. Instead, the
simple-jet mode, which operates at much higher flowrates than the cone-jet mode, is
recommended for such applications. This mode can also produce monodispersed droplets,
but larger than in the former mode for the same liquid properties. This mode is not as much
explored as the cone-jet mode. This work was carried out in order to understand the simplejet
mode of electrospray further, so as to design appropriate systems that depend on this
mode.In this work, a physical model for determining the droplet trajectories in the simple-jet
mode was designed and implemented. The model was designed to solve the force balance
equation, in two dimension (to ensure minimum computational time as opposed to a 3D
environment) for each droplet breaking up from the jet. Deformation of the droplets was
disclosed to be the major cause of the droplets’ initial displacement from the Y- axis.
However, a model in a 3D environment is recommended to confirm the findings in this
model.
After validating the model, by comparing the theoretical and experimental droplets’
trajectories, qualitatively and quantitatively, different components of force acting on the
droplets were analyzed. Out of this analysis, an air flow was recommended and
investigated to manipulate the droplets’ trajectories.
In order to investigate the effect of wind on the droplets’ trajectories in the model, the
packing factor for the droplets was analyzed. An air flow was then introduced to the spray
at a certain point below the breakup point where the packing factor was low. Similar spray
deflection was observed in the model and in the experiment. This was after making an
assumption of a uniform velocity field for wind in the model.
This model can be used to provide design pre-parameters for those systems that depend on
atomization methods at high throughput. It also introduces the possibility of calculating the
droplets trajectories with the introduction of extra forces.
Citation
Degree of Master of Science in Nuclear Science at the Institute of Nuclear Science and TechnologyPublisher
University of Nairobi