Multiphysics Modeling of Industrial Top Coating with Rotary Bells 2024-01-2679

Rotary Bell Atomizers are well established in the automotive industry for top coating applications. This type of atomizer allows to create a uniform coating and is characterized by high productivity. Meanwhile, the effectiveness of the process depends on many complex factors. For instance, the transfer efficiency of the paint material, which is the percentage of the paint reaching the structure surface, ranges from 60-95% depending on the application conditions. Any increase in the transfer efficiency can not only reduce energy and material costs, but also reduce the emission of harmful non-deposited paint particles and the effort to handle them. The use of accurate numerical methods in this process helps to optimize the application process, reduce the number of expensive field experiments, and shortens the development cycle of new vehicles, which ensures predictability of production costs. This paper describes a multidisciplinary framework that allows to simulate the industrial processes of coating paint quickly with high accuracy on complex car geometries. Film deposition of paint droplets on the target, the movement of paint particles between the target and the atomizer and the effect of a swirling air jet on the droplet trajectory are all considered. The complex atomization around the bell cup is replaced by a statistical droplet generator. Furthermore, to speed up the simulation, a simplified version of the complex shaping air system is proposed in the work. To model the process, a coupled multi-physics solver is developed, which combines lattice Boltzmann method for air flow, Lagrangian particle method for paint droplets, and the thin film solver for coating thickness calculation. The paper presents the physical and mathematical model of the process, brief introduction on the numerical methodology, validation results based on experimental data, and the results of modelling practical coating scenarios. Results show that the proposed approach has high reliability and can be applied to accurate top coating simulation and the related process/design optimization.