Circumferential Spray Patternation of the Pressure-Swirl Atomizers

Pressure-swirl atomizers (PSAs) are commonly used in aerospace engines and various industrial settings. Even though the design of PSAs is simple, the internal flow dynamics can be quite complex due to the presence of swirling motion, turbulence, and an air core. While certain parameters such as spray angle and droplet distribution have been widely studied and modeled, the circumferential distribution of the atomizer flow is not well understood. The objectives of this study are to identify the cause of non-uniformity in the spray produced by PSAs and to develop a uniformity model to predict the level of circumferential patternation of spray. To accomplish this, 3D numerical simulations were run on a range of PSAs, and three atomizers were fabricated using laser-lithography to ensure maximum manufacturing precision. Of the fabricated atomizers, two exhibited uniform distributions, while the other had deficiencies in both internal and external flow fields. LIF/Mie experiments on a radial plane and high-speed images on central axial plane of the manufactured atomizers were conducted.The results indicated that non-uniformity in the internal flow greatly impacts downstream droplet distribution. The root cause of non-uniformity was determined to be the interaction of inlet flows as they enter the swirl chamber. A new semi-empirical uniformity model, based on experimental data, was developed and found to be more accurate than existing models.