Modeling and simulation of air-assist atomizers with applications to food sprays

• The CAB model was modified to accommodate air-assist atomization for food sprays.
• The relative velocity between the liquid and the gas at the nozzle exit was modeled.
• The drop size distributions of the product droplets were modified.
• The model was validated with experimental data for oil-in-water emulsion sprays.
• Good agreement was obtained with the experimental data.

The Cascade Atomization and Drop Breakup (CAB) model has been developed originally for pressure atomizers. In this study, the CAB model is modified to accommodate air-assist atomization. The modifications include a change in the product drop distributions, namely, the uniform distribution used in the original CAB model is replaced with a χ-squared distribution with the same average drop size. The second modification addresses the air-assist atomization process. This process is modeled by estimating the Weber number due to the increased relative velocity caused by the air flow. Depending on the value of the Weber number this leads to a catastrophic, or a stripping (sheet-thinning), or a bag breakup. The model changes are validated with experimental data obtained from two different air-assist atomizers using an oil-in-water emulsion. The simulations were performed with a modified version of the KIVA-3 CFD code, and they showed good agreement with the experimental data.