GOALI: Liquid Charging in Electrostatic Atomizers for Coating and Painting Applications

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The focus of this proposal is to investigate the process of the generation of electrical charges at the nozzles of sprays. This work will be done in collaboration with an industrial partner, Spraying Systems Company (SSCo), a large international manufacturer of spray products with a well-equipped research lab near the University of Illinois at Chicago. The co-PIs already have an on-going collaboration with SSCo. The motivation for the proposed research is to facilitate the commercialization of the electrostatic atomizers for coating and painting applications. Both of these applications would benefit significantly from the ability to control drop trajectories to avoid waste, provide precision deposition, and reduce the spread of hazardous materials. The proposed work aims at providing the understanding needed to achieve these performance characteristics. In addition, a low-cost computational model as a predictive tool for the design of these atomizers will be developed. The proposal includes concurrent studies based on theory, computation and experiments. This is a multiscale problem that will be tackled by theory to separate the analysis of the extremely thin near-electrode polarized layer, where an imbalance of charges exists, from the analysis of the electroneutral bulk flow with much larger dimensions. As a result of this separation, one would only need to solve for a Laplace equation (for the electric potential) along with the Navier-Stokes equations in the incompressible bulk flow. The solution of the Laplace and Navier-Stokes equations, which are coupled through the boundary conditions at the electrode, will be obtained numerically. Experiments are also proposed to (i) determine an empirical coefficient for the rate of reaction at the electrode surface, and (ii) provide data for validation of the computational model. The validated model will be implemented to conduct a detailed study on the effect of various parameters, such as the shape of the electrode. Collaboration with SSCo will provide experimental data for model validation and will facilitate the scale-up of the process. Broader impacts include industrial outreach and involvement of undergraduates and graduate students; creation of animations demonstrating the charging process. A successful electrostatic atomizer for non-conducting liquids will provide great advantages in sprays and coatings, which are materials that surround us and we use in everyday life.