ID 180

Primary breakup of non-Newtonian liquids in the near-field of a high-speed rotary bell atomizer for spray painting processes

 

Abstract:

The present contribution deals with numerical and experimental studies of the primary liquid breakup process using a high-speed rotary bell atomizer. The investigation focuses on the disintegration process of the paint liquid in the near-bell region. The volume of fluid (VOF) approach and Reynolds stress model are used in the CFD software Ansys Fluent to study the disintegration process and the two phase flow field. As inlet conditions for the breakup simulations, the properties of the liquid film at the bell edge, i.e., film thickness, velocities and apparent viscosity, resulting from our previous work were applied. The paint liquid used in the studies has shear-thinning (pseudoplastic) behavior, measured by rotational and capillary viscometers. Two different liquid disintegrations in the near-field are found, which are also observed in experimental investigations using a high-speed camera. Furthermore, user defined functions (UDFs) were compiled in Ansys Fluent to detect droplets resulting in the breakup process. The droplet properties, such as volume, equivalent diameter, velocity and position, can be determined in this way. The quantitative analysis based on the simulation data, i.e., the droplet size distribution, will be compared with the experimental results by means of a high-speed camera.