High-fidelity simulations of a rotary bell atomizer with electrohydrodynamic effects

Electrostatic rotary bell atomizers are extensively used as paint applicators in the automobile industry. Paint undergoes atomization after exiting the edge of a high-speed rotating bell. In most setups, the paint is electrically charged and a background electric field is applied between the nozzle and the target surface to increase the transfer efficiency (TE). The atomization process directly determines the droplet size and droplet charge distributions which subsequently control TE and surface finish quality. Optimal spray parameters used in industry are often obtained from expensive trial-and-error methods. In this work, three-dimensional near-bell atomization is computationally simulated using a high-fidelity volume-of-fluid transport scheme that includes electrohydrodynamic (EHD) effects. We find that electrifying the setup results in the production of smaller droplets. Additionally, the electric field has a minor effect on primary atomization but a negligible effect on the size and stability of atomized droplets after secondary breakup. This cost-effective method of simulating EHD-assisted atomization allows for the understanding of the effect of the electric field and the extraction of droplet charge characteristics which is otherwise challenging to obtain experimentally.

Automated summary

Electrostatic rotary bell atomizers are commonly used in the automobile industry to apply paint. A computational simulation of three-dimensional near-bell atomization is performed in this work to investigate the effect of electrification on droplet size and charge characteristics. The results show that electrifying the setup leads to the production of smaller droplets and the electric field has a minor effect on primary atomization but a negligible effect on the size and stability of atomized droplets after secondary breakup. This cost-effective simulation method provides insights into the influence of the electric field in atomization.