Numerical simulation investigation of the mechanism of lacquer curtain formation in curtain coating

Abstract

To study the key factors on integrated curtain formation and breakup in curtain coating production process, we used the numerical simulation method to analyze the various stages of the curtains from full curtain to full thread state by changing the inlet flow rate, which is, changing the Weber number (We). The numerical model was based on an actual production machine, and the physical properties of the lacquer were accurately measured for the simulation. It is found that with the gradual breakup of the curtain, the oscillation of the curtain gradually increased, there was obvious distortion and increase in Turbulent Viscosity Ratio (TVR) at the breakup, and there was a decrease in Dynamic Pressure (DP) at the top of the breakup. Different curtain state reflects a shift from inertia force dominance to a balance of forces and finally to surface tension dominance. The finding from the simulation, also the comparison between the results of simulation and experiments provided the basis to understand the mechanism of curtain coating, also inspired the engineers to optimize the geometry of curtain coater and the coating production parameters for easier integrated curtain forming.