Authors: J. Hua, L.K. Lim, C-H Wang
Affilation: Institute of High Performance Computing, Singapore
Pages: 378 - 381
Keywords: droplet formation, particle fabrication, EHDA, multiphase flow, CFD simulation
Electrohydrodynamic Atomization (EHDA) is a method to disperse liquid jet into micro- droplets where an electrical field is applied to control the breakup characteristic of the liquid jet. Recent studies show that EHDA method is also useful in the production of polymeric microparticles. This can be achieved by dissolving the polymeric substrate in an organic solvent and spraying it using EHDA. As the solvent evaporating from the droplet surface, solid polymeric particles can be formed. The size of the fabricated particles can be varied from micrometer to nanometer range by adjusting the EHDA operating parameters such as electrical potential difference, liquid flow rate, nozzle size, spraying environment, solvent property, etc. The properties of the fabricated particles under different operation conditions were also investigated. In the experimental study, different EHDA spray modes under various operation conditions were observed. In addition, we also investigated the formation of liquid droplets from the Single Taylor Cone Jet mode in EHDA by numerical simulation. The shape of the liquid/gas interface formed at the tip of the nozzle is a result of the balance of liquid pressure, surface tension, gravity, electric stress on the liquid surface, inertia, and viscosity. Computational fluid dynamic simulations were also used to examine the EHDA Taylor Cone Jet formation process by solving the incompressible Navier-Stokes equation for both liquid and gas phases, tracking the fluid/gas interface using a front tracking method, and taking into account the effects of electric stress on the fluid/gas interface. Different operating parameters, such as nozzle and ring electrical potential difference, nozzle size, liquid flow rate, liquid properties (viscosity and surface tension), were varied to study their effects on Taylor Cone jet formation and droplet size. The results show that, with prior knowledge of the operating parameters, it is possible to control the size of the particles fabricated by an EHDA method.