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Atomization, droplet on demand, and coating

In automotive painting, the transfer efficiency using rotary bell atomizers is in the range of 50-60% [1], this means that large amount of paint and energy is wasted. The understanding of droplets atomization and transport is therefore essential to solve this dilemma. At IR4TD, we designed novel infrared flow visualization technique [2, 3], to investigate the effect of different operating parameters on the flow dynamics and transport of rotary bell sprays. We have also designed a novel schlieren imaging application [4] to visualize the rotary bell shaping air free of air-droplet interaction, which was not previously possible using other technologies. With that, we were able to examine the effect of various running conditions on the shaping air by itself, which in turn advanced our understanding of the compounded effects they had on droplets transport. Additionally, we have experimentally investigated  and mapped the droplet size distribution inside the spray for over 500 different running conditions using laser diffraction and shadowgraph techniques [5, 6], which provided insights on Sauter diameter distribution in the spray profile, as well as a huge database for simulations validation.

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References

1. Akafuah, N.K., et al., Evolution of the automotive body coating process—A review. Coatings, 2016. 6(2): p. 24.

2. Akafuah, N.K., A.J. Salazar, and K. Saito, Infrared thermography-based visualization of droplet transport in liquid sprays. Infrared Physics & Technology, 2010. 53(3): p. 218-226.

3. Akafuah, N.K., Visualization and characterization of ultrasonic cavitating atomizer and other automotive paint sprayers using infrared thermography. (Doctoral dissertation), Department of Mechanical Engineering, University of Kentucky, 2009.

4. Darwish Ahmad, A., et al., Schlieren visualization of shaping air during operation of an electrostatic rotary bell sprayer: Impact of shaping air on droplet atomization and transport. Coatings, 2018. 8(8): p. 279.

5. Wilson, J., et al., Study of Near-Cup Droplet Breakup of an Automotive Electrostatic Rotary Bell (ESRB) Atomizer Using High-Speed Shadowgraph Imaging. Coatings, 2018. 8(5): p. 174.

6. Darwish Ahmad, A., et al., Spatial Positioning and Operating Parameters of a Rotary Bell Sprayer: 3D Mapping of Droplet Size Distributions. Fluids, 2019. 4(3): p. 165.