Numerical Investigation of Electrostatic Spray Painting Transfer Processes for Vehicle Coating

In this study we examined numerically the electrostatic spray transfer processes in the rotary bell spray applicator, which is this case implemented in a full 3D representation. Instead of an experimental approach [Stevenin et al., 2015, Fluids Eng., 137 (11)], here an algorithm implemented and developed for this simulation includes airflow, spray dynamics, tracking of paint droplets and an electrostatic modularized solver to present atomization and in-flight spray phenomena for the spray forming procedure. The algorithm is implemented using the OpenFOAM package. The shaping airflow is simulated via an unsteady 3D compressible Navier-Stokes method. Solver for particle trajectory was developed to illustrate the process of spray transport and also the interaction of airflow and particle that is solved by momentum coupling. As the numerical results in this paper indicates dominant operating parameter voltage setting, further the charge to mass ratio and air-paint flow rate deeply effect the spray shape and the transfer efficiency (TE). The spin of the bell forced the paint to fall off from the bell edge into the high-velocity airflow. By increasing the shaping airflow more uniform distribution of mass of paint is produced but the TE decreases. The size distribution is highly sensitive to the bell rotational speed. Our results demonstrate the validity of the numerical procedure and also the applicability of it in reducing the production costs for painting. Unsteady and dynamic treatment of the flow is described using Large eddy simulation (LES) turbulence models, whereas the movement of the paint particles is modeled by the approach of tracking droplet size distribution, also the electrical potential effect on its size and form can be predicted. Using this advanced numerical simulation the efficiency and quality of the program can be evaluated precisely for industrial robots of paint over Off-Line Programming (OLP). Further, the paint spraym structure obtained from the numerical simulations is compared with the experimental data at the same working condition with appropriate quantitative accuracy. © 2019 SAE International. All Rights Reserved.