Formation of Görtler vortices in an open-end pressure swirl atomizer

In pressure swirl atomizers, a two-phase swirling flow occurs when liquid is introduced through tangential ports into the swirl chamber. Due to the interactions among jets from neighboring inlets, flow instabilities and non-uniform spray patterns can occur. These three-dimensional effects raise concerns about the accuracy of two-dimensional axisymmetric simulations. The authors investigate whether a purely axisymmetric ring-like inlet surface can eliminate flow non-uniformities, although such designs often require exceptional inlet configurations. This study focuses on open-end pressure swirl atomizers, as closed-end designs are more prone to separation downstream of contraction. High-fidelity three-dimensional flow simulations using the Volume of Fluid and Quasi Direct Numerical Simulation methods are performed. While the primary performance parameters—such as discharge coefficient and spray angle—show no significant differences between two-dimensional and three-dimensional simulations, the three-dimensional simulations reveal Görtler vortices within the liquid film. Although these vortices lead to slight differences in velocity profiles, they contribute to a vortical non-uniform velocity field at the injector exit, resulting in wrinkled waves in the spray film. Furthermore, simulation with axial swirling film inlet condition indicates that Görtler vortices can develop without flow separation, still causing spray film wrinkling. These findings suggest that Görtler vortices can negatively impact atomization and lead to non-uniform spray distribution, regardless of the inlet quality.