Numerical calculation of electrostatic powder painting using the Euler/Lagrange approach

Numerical calculations of gas-particle flows involving an electrical field, as they are found in the powder painting process, are presented based on the Euler/Lagrange approach. The gas flow is calculated by solving the Reynolds-averaged Navier-Stokes equations including the k-epsilon turbulence model. In order to solve the Laplace equation for the electrostatic field, a finite-volume approach is applied. The particle phase is simulated by using a Lagrangian treatment where a large number of particles are tracked through the flow and the electrostatic field. In addition to the drag and gravity, also, the electric field force is considered in the equation of motion. Average properties of the particle phase are obtained by ensemble averaging. The method is applied to the powder painting process. Two types of powder guns were considered, a slit nozzle and a round nozzle with a dispersion cone. The calculated general flow structure in the vicinity of the painting gun and the large-scale flow within the painting booth agreed reasonably well with the experimental observations. Additionally, the coating layer thickness was used for comparison, which is also relevant to judge the quality of the coating process. The results showed a reasonable good agreement between calculations and measurements for the slit nozzle. However, the extent of the paint layer was remarkably under-predicted for the round nozzle, which is mainly caused by the complex flow in this case. Nevertheless, the results demonstrate that numerical calculations are useful and effective for supporting the design and optimization of powder painting booths. (C) 2002 Elsevier Science B.V. All rights reserved.