Numerical simulation of liquid sheet formation and primary atomization in a simplex pressure-swirl atomizer through a VOF-LES approach

Numerical simulations of the atomization issued by pressure-swirl injectors can help improve their design to reduce CO₂ and NO_x power plant emissions. In particular, two-phase flow simulations allow the characterization of the resulting spray through characteristic droplet sizes and velocities. This computational work focuses on the liquid atomization of n-heptane in the simplex pressure-swirl atomizer of the CORIA Rouen Spray Burner (CRSB). The present work proposes the simultaneous numerical resolution of the internal flow and atomization development through a Volume of Fluid-Large Eddy Simulation (VOF-LES) approach using a hexahedral mesh and Adaptive Mesh Refinement (AMR). A nonreactive condition has been tested with the interIsoFoam solver of the OpenFOAM open-source toolbox. First, the achieved results are analyzed in terms of qualitative properties, such as spray development and vortex visualization. Then, the internal flow is studied from both the air core radius and the film thickness evolution along the axial length. Finally, droplet statistics are obtained through a droplet detection algorithm based on a volume fraction threshold. For validation purposes, the numerical results are compared with available Phase Doppler Anemometry (PDA) experimental data for this operating condition of the CRSB academic burner. The investigation demonstrates the capability of the proposed numerical methodology to predict the physics under the primary atomization process, allowing us to describe the air core formation and to capture the instabilities that trigger the jet breakup, leading to the spray evolution.