MODELING THE EFFECTS OF OPERATING PARAMETERS ON THE PAINT TRAJECTORIES FOR AN ELECTROSTATIC ROTARY BELL ATOMIZER

There are many variables that affect the electrostatic painting process such as the atomizer geometry, liquid paint properties, target shape, atomizer-to-target distance, liquid paint flow rate, bell speed, shaping air flow rate and electrical voltage. With the aid of FLUENT software, it is possible to model the painting process in configuration with complex geometry and turbulent shaping air to determine the paint droplet trajectories and to optimize this process. In this paper, an electrostatic rotary bell painting process was modeled assuming mono-disperse size paint particles. The effects of the operating parameters were analyzed for the droplet spatial concentration, trajectories, transfer efficiency and target surface coverage uniformity. The results showed that the paint transfer efficiency increases with the droplet charge-to-mass ratio within a certain range. The droplet size needs to be controlled in order to balance the transfer efficiency and the surface quality. The bell speed and liquid flow rate mainly influence the droplet size; the shaping air and the atomizer-to-target distance together determine the proper droplet terminal velocity and the target diameter affects the transfer efficiency.