Paint and Spray Technology

a picture of spray experiment

 

IR4TD's paint and spray technology research focuses on advancing coating processes, especially in the automotive industry, by optimizing paint application systems, improving efficiency, and minimizing environmental impacts. The team, led by Dr. Nelson Akafuah, utilizes advanced techniques such as infrared thermography, schlieren imaging, laser diffraction, and high-speed photography to study the atomization, transport, and deposition of paint droplets from rotary bell sprayers and electrostatic systems. These sprayers offer high-quality finishes with improved transfer efficiency. IR4TD's research explores factors such as droplet size distribution, shaping air effects, and the impact of sprayer operating parameters like rotational speed and flow rate. Additionally, the research extends to the development of innovative coating detection methods using color-based thermal mismatch to identify defects in coatings. The team seeks to enhance spray coating performance, reduce material waste and defects, and lower volatile organic compound (VOC) emissions through computational simulations and experimental methods, making the process more sustainable and cost-effective. This experience positions IR4TD at the forefront of automotive paint technology and other spray application innovations. 

 

 

Our Paint and Spray Technology Highlights

 

 

 

 

Thin Liquid Films on a Rotary Bell Atomizer in Surface-Following Coordinates

Journal of Coatings Technology and Research (2022) by Mark Doerre and Nelson Akafuah

 

This paper examines the fluid dynamics of paint application in automotive manufacturing using rotary bell atomizers, a crucial technology in automotive spray painting. The study presents a mathematical analysis of how thin liquid films behave as they are spread across the surface of a rapidly spinning bell before being atomized and sprayed onto a target surface, such as a car body. The research highlights the use of surface-following coordinates, which provide more accurate predictions of paint film behavior compared to traditional cylindrical or spherical coordinate systems. By analyzing the flow of paint as it moves outward from the center of the rotary bell to its periphery, the paper shows how variables such as angular velocity, fluid viscosity, and bell design influence the atomization process and droplet formation. These insights are critical for achieving uniform paint distribution, improving the efficiency of the spraying process, and enhancing the overall finish quality. The study’s findings can be applied to optimize rotary bell sprayer performance in industrial settings, particularly for automotive manufacturers seeking to improve paint coverage, reduce material waste, and achieve a flawless surface finish.  

 

Spatial Positioning and Operating Parameters of a Rotary Bell Sprayer: 3D Mapping of Droplet Size Distributions

Fluids (2019) by Adnan Darwish Ahmad, Binit B. Singh, Mark Doerr, Ahmad M. Abubaker, Masoud Arabghahestani, Ahmad A. Salaimeh, and Nelson Akafuah  

 

 

IR4TD researchers investigated how various operating parameters, such as flow rates and rotational speeds, affect droplet sizes in spray painting processes. By using advanced 3D mapping, the study demonstrated that higher rotational speeds reduce droplet size, while higher flow rates increase it. This research emphasized that the dominant factor in droplet size reduction is the rotational speed of the rotary bell sprayer, which is critical for achieving uniform paint distribution. The study's findings are especially relevant for automotive paint applications, where precise control over droplet size ensures an even coating, improved transfer efficiency, and minimized waste. Additionally, the experimental results validated the theoretical models, offering a reliable framework for future studies and practical applications in the painting industry.

 

 

 

Evolution of the Automotive Body Coating Process-A Review

Coatings (2016) by Nelson Akafuah, Sadegh Poozesh, Ahmand Salaimeh, Gabriela Patrick, Kevin Lawler, and Kozo Saito  

Collaborator: Toyota Motor Engineering and Manufacturing North America, Inc. (TMNA)

 

This paper offers a detailed exploration of the history, developments, and future trends in automotive coatings. Initially, cars were painted with varnish that required manual application and multiple layers, taking up to 40 days to complete. With the introduction of spray technology in the 1920s, the coating process became more efficient, reducing time to a week. Further advancements like nitrocellulose lacquers and alkyd enamels improved durability and color options. The 1960s saw the advent of acrylic enamels, providing greater resistance to environmental factors. The paper also discusses modern coating processes, which involve five main steps: pretreatment, electrodeposition for anti-corrosion, application of sealers, primers, and topcoats (basecoat and clearcoat). These advancements improved durability, appearance, and environmental compliance. Innovations like smart coatings with self-healing properties and smart sensors represent the future of automotive coatings. Additionally, techniques such as powder coatings and water-based primers are now more prevalent due to their environmental benefits, signaling a shift toward more sustainable practices in automotive manufacturing. The review concludes by discussing emerging technologies, such as self-stratifying coatings, that promise even greater efficiency and functionality.

Other Paint and Spray Technology Papers

1. A CFD-based scaling analysis on liquid and paint droplets moving through a weak concurrent airflow stream in Progress in Scale Modeling (2022) by Masoud Arabghahestani, Nelson Akafuah, Tianxiang Li, and Kozo Saito 

2. Integrating a model predictive control into a spray dryer simulator for a closed-loop control strategy in International Journal of Heat and Mass Transfer (2021) by Sadegh Poozesh, Marc Karam, Nelson Akafuah, and Yifen Wang 

Collaborator: Mechanical Engineering Department and Electrical Engineering Department, Tuskegee University, and Biosystems Engineering Department, Auburn University 

3. Computational fluid dynamics and scaling study on ultrasonic pulsation atomizer for waterborne paint in Atomization and Sprays (2021) by Masoud Arabghahestani, Nelson Akafuah, and Kozo Saito 

4. Experimental and mathematical tools to predict droplet size and velocity distribution for a two-fluid nozzle in Fluids (2020) by Sadegh Poozesh, Nelson Akafuah, Heather Campbell, Faezeh Bashiri, and Kozo Saito 

Collaborator: College of Pharmacy, University of Kentucky, and Electrical and Computer Engineering, University of New Brunswick 

5. Interrogation of a new inline multi-bin cyclone for sorting of produced powders of a lab-scale spray dryer in Powder Technology (2020) by Sadegh Poozesh, Seidd Mahdi Jafari, and Nelson Akafuah 

Collaborator: Food Materials and Process Design Engineering Department, Gorgan University of Agricultural Sciences and Natural Resources 

6. Reduction of order: Analytical solution of film formation in the electrostatic rotary bell sprayer in Symmetry (2019) by Mark Doerre and Nelson Akafuah 

7. Schlieren Visualization of Shaping Air during Operation of an Electrostatic Rotary Bell Sprayer: Impact of Shaping Air on Droplet Atomization and Transport in Coatings (2018) by Adnan Darwish Ahmad, Ahmad Abubaker, Ahmad Salaimeh, and Nelson Akafuah 

8. Effects of automotive paint spray technology on the paint transfer efficiency – a review in Proceeding of the Institute of Mechanical Engineers, Part D: Journal of Automobile (2018) by Sadegh Poozesh, Nelson Akafua, and Kozo Saito 

For more research output on Paint and Spray Technology, please visit Scholars@UK.