Modified TAB Model for Viscous Fluids applied to Breakup in Rotary Bell Spray Painting

Paper in proceedings, 2012

The Taylor Analogy Breakup (TAB) model is applied to droplet breakup in rotary bell spray painting commonly used in the automotive industry. The bell spins rapidly around its axis with a tangential velocity at the edge in the order of 100 m/s. The paint falls off the edge and enters the air with a large relative velocity, driving the atomization. The paint is a viscous fluid and a modification of the TAB model taking non-linear effects of large viscosity into account is described. The parameters in the breakup model are tuned to match droplet size distributions obtained in CFD simulations with measured ones. Results are presented for three cases with rotation speeds from 30 to 50 thousand RPM where the full droplet size distributions are compared with measurements. Good results are obtained for all three cases where the simulated size distributions compare well to measurements over a wide range of droplet sizes. The obtained results can be used in a preprocessing stage of a full spray painting simulation thereby reducing the need for costly and cumbersome measurements.