Research on Film-Forming Characteristics and Mechanism of Painting V-Shaped Surfaces

Abstract

Painting a V-shaped surface, which is widely found in various facilities and equipment, often results in poor coating quality, which may be caused by an insufficient understanding of film-forming characteristics and mechanism. In this study, computational fluid dynamic (CFD) simulations were carried out for in-depth research on the film-forming characteristics and mechanism of painting V-shaped surfaces. The mathematical model of film formation was established with the Euler–Euler method, and the unstructured grids and adaptive-mesh refinement were adopted to discretize the computational domain. By solving the model, the coating thickness distribution law and flow-field characteristics of spraying a V-shaped surface were obtained. When painting a V-shaped surface with an angle less than 180°, the coating thickness distribution appeared as two peaks, instead of the single peak that appeared when painting a flat wall. As the V-shaped angle decreased, the coating thickness became thinner. The peak position gradually shifted to both sides, and the thickness distribution became wider. Analysis of the spray flow-field characteristics revealed the thickness distribution mechanism, by whichthe geometric characteristics of the V-shaped surface changed the near-wall distribution of the flow field. When the V-shaped angle decreased, the pressure peak at the center of the V-shaped surface and the eccentric pressure peaks that formed on both sides increased. The near-wall paint fluid was confined between the central pressure peak and the off-center pressure peak, resulting in paint droplets depositing between the pressure peaks and double-peak distribution of the coating thickness forming on the V-shaped surface. The spraying experiments verified the correctness of the numerical simulations, film-forming characteristics, and corresponding mechanism, which are of great significance for efficient and high-quality spraying on V-shaped surfaces.

A Review of the Developments of the Characteristics and Mechanisms of Airless Spraying on Complex Surfaces

“…Ye et al [108] carried out a numerical simulation of spray film formation with variable gun pressure on a right-angled slot surface of a car body. Chen et al [109,110] also studied the film formation characteristics of V-shaped surface spraying with different connecting angles based on the VOF model, and the simulation results obtained were in good agreement with the coating thickness obtained from the experiments.…”

A CFD-DEM Simulation of Droplets in an Airless Spray Coating Process of a Square Duct

“…The results produce a straight line in the increasing region using regression analysis. The relationship can be expressed approximately as θ = −100.24 + 20.52 ln γ (19) Coatings 2024, 14, 282 8 of 23 In case II, the AoR trends to zero with decreasing wall-paint droplet surface energy in the moderating region. A droplet layer is formed, representing a droplet film on the flat plate.…”

“…The predicted droplet diameter distribution using OpenFOAM code was compared to experimental data in the spray atomization. The formation of coating film was modeled using the Euler-Euler approach in the static spraying and dynamic spraying processes [19]. The film formation and thickness distribution were predicted in a V-shaped surface with an air cap of a spray gun.…”

Dynamic Numerical Simulation of Curved Surface Coating Trajectory Based on STL Slicing Algorithm

“…Ye et al [22] discovered a correlation between droplet particle size distribution and atomization air volume as well as forming air volume. Chen et al [23] investigated the distribution of V-shaped surface coatings and observed a bimodal distribution in coating thickness. Chen et al [24] conducted research indicating that the coating thickness of the arc section is greater than that of the plane section.…”