ELECTRICAL CHARACTERIZATION OF BELL-TYPE ELECTROSTATIC PAINTING SYSTEMS

A numerical model that determines the electrical characteristics of a bell-type electrostatic painting system is presented. The model is capable of handling the complex geometries of practical sprayers and accounts for the space charge effect of charged paint droplets. The influence of aerodynamic forces are also considered in tracing individual droplet trajectories. As a test of the simulation, the restricted case of a sprayer emitting ions, rather than charged paint droplets, was modeled. The simulation results were compared with experimental data and showed good agreement. For the more general case, maps of equipotential contours and the paint droplet trajectories are generated for a bell-type sprayer. It was found that the space charge tends to increase the deposition field although not as strongly as increased bell potential or decreased bell to target spacing. However, the space charge also caused the spray pattern to expand, possibly leading to increased overspray.