In the present investigations, phase-Doppler anemometry has been used to perform detailed measurements in the spray painting process including the spray cone and the vicinity of the substrate. Supplementary, techniques have been applied to investigate the quality of the layer on the substrate itself. It could be shown, that the mean droplet diameters obtained in the spray cone of a water borne paint spray are a strong function of the distance from the target, indicating the loss of small droplets following the radially directed air flow near the target, as expected. These small droplets form the so-called overspray, i.e. the fraction of paint which does not reach the substrate.
The experimental results have been used as input data for a numerical program for the calculation of two-phase flows based on the time-averaged Navier-Stokes equations in connection with the k-ε turbulence model and the Lagrangian particle tracking method. Due to the three-dimensional abilities of this program the true flat cone of a air spray gun could be simulated. In addition to the fluid and particle flow field, also the transfer efficiency and the layer formation could be calculated. A very good agreement between calculations and measurements with respect to the layer thickness distribution was found. Furthermore, measured and calculated transfer efficiencies agree within less than 2 %. Thus, the developed program represents an excellent tool for a future optimization of the spray coating process.