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Electrostatic rotary bell atomizers are commonly used in several engineering applications, including the automobile industry. A high-speed rotating nozzle operating in a strong background electric field atomizes paint into charged droplets that range from a few micrometers to tens of micrometers in diameter. The atomization process directly determines the droplet size and droplet charge distributions which subsequently control the transfer efficiency and the surface finish quality. We have previously developed a tool to perform high fidelity simulations of near-bell atomization with electrohydrodynamic effects. In this work, we perform simulations employed with a droplet ancestry extraction tool to analyze previously inaccessible information and understand the physical processes driving atomization. We find that the electric field accelerates breakup processes and enhances secondary atomization. The total number of droplets, the ratio of secondary to primary droplets, and the ratio of coalescence to breakup activity are all much higher when operating in an electric field. We analyze the droplet velocity, local Weber number and charge density statistics to understand the complex physics in electrically assisted breakup. The results of the study have helped us gain insights into the physics of atomization in electrostatic rotary sprays.
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High-fidelity simulation of a rotary bell atomizer with electrohydrodynamic effects
Rotary Bell Atomizers (RBA) are extensively used as paint applicators in the automotive industry. Atomization of paint is achieved by a bell cup rotating at speeds of 40k-60k RPM in the presence of a background electric field. Automotive paint shops amount up to 70% of the total energy costs [Galitsky et. al., 2008], 50% of the electricity demand [Leven et. al., 2001] and up to 80% of the environmental concerns [Geffen et al., 2000] in an automobile manufacturing facility. The atomization process in an RBA affects droplet size and velocity distribution which subsequently control transfer efficiency 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-cup atomization (primary and secondary breakup) are simulated computationally using a high-fidelity volume-of-fluid transport scheme that includes an electrohydrodynamic effects. The influence of fluid properties (viscosity ratio, flow rate and charge density), nozzle rotation rate and bell potential on atomization are investigated by performing a parametric study. This cost-effective method of research aims to identify the ideal spray parameters to achieve maximum transfer efficiency.
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- Award ID(s):
- 1749779
- PAR ID:
- 10324145
- Date Published:
- Journal Name:
- ICLASS 2021, 15th Triennial International Conference on Liquid Atomization and Spray Systems
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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