A Numerical Investigation of the Factor Decreasing Transfer Efficiency in a High-Speed Rotary Bell-Cup Atomizer

A simulation of spray flow around a high-speed rotary bell-cup was carried out in order to determine the dominating factor decreasing the transfer efficiency. The effect of the inner re-circulation flow and the ghost on the transfer efficiency was numerically investigated by a detailed comparison of adhering and non-adhering droplets. The spray flow was calculated based on the Euler-Lagrangian approach, including the standard k-epsilon turbulence model. It was found that the inner re-circulation flow tends to draw in small droplets, and that droplets located at inner side of radial direction tend not to adhere to the target. The ghost is composed of large droplets. In the ghost, the adhering and non-adhering droplets have different trajectories. These findings indicate that the inner re-circulation flow and the ghost have a large effect on small and large droplets, respectively. The location of droplets in the inner re-circulation flow or the ghost is important for the transfer efficiency.