Numerical simulations of particle-laden turbulent flows to characterize the two different types of paint spray; Bell-cup atomizer and powder spray gun

The motions of particles injected from two different sprayers were investigated. The present investigation deals with automotive paint sprayers, a high-speed rotary bell-cup atomizer and a powder spray gun. The liquid droplets and powder coatings in each paint system were modeled as undeformable spherical particles, and the two-phase flow was numerically computed with the Euler-Lagrange approach. The Reynolds averaged Navier-Stokes equation was solved with the standard k- model. As a result, despite the difference in spray system, the spread of spray near the nozzle, so called ghost, was observed in both sprayers. When electric voltage was applied, the bell-cup atomizer had relatively strong tendencies of the motion behavior of paint particles compared with powder spray gun: (a) large particles in ghost propagated radially outward and missed the target, and (b) the transfer efficiency was sensible to Sauter mean diameter. On the other hand, when zero electric voltage was applied, an opposite trend was observed. Thus, in the case of the industrial spray process using bell-cup atomizers with high voltage, the control technique of the particle diameter might be of great significance in order to improve transfer efficiency.