Modelling the Flow Conditions and Primary Atomization of an Air-Core-Liquid-Ring (ACLR) Atomizer Using a Coupled Eulerian–Lagrangian Approach

The Air-Core-Liquid-Ring atomizer is a pioneering internal-mixing pneumatic atomization technique designed for energy-efficient spray drying of highly viscous liquid feeds with substantial solid contents. However, it can suffer internal flow instabilities, which may lead to spray droplets with a wide variation in diameter. Experimental investigation of how flow conditions mechanistically determine the resulting droplet sizes is hindered by high velocities near the nozzle outlet. Therefore, this study addressed the issue by implementing a numerical model, employing a coupled Eulerian-Lagrangian approach with adaptive mesh refinement, to simulate the breakup of the liquid into ligaments and droplets. Additionally, Large Eddy Simulation was incorporated to replicate turbulent flow conditions observed in experiments. The numerical model demonstrated significant improvement in predicting liquid film thickness, compared to previous work. Additionally, the simulated droplet size distributions mirrored experimental trends, shifting to smaller sizes as pressure increased. Unfortunately, while reduced, there is a persistent underestimation of the lamella thickness and the droplet sizes at 0.2 MPa. In spite of this, the fact that the error propagates between the two phenomena underscores the effective coupling between Eulerian and Lagrangian approaches.