Morphologies and structures of liquid fragments derived from the near-field zone of a twin-orifice swirl atomizer.

Aviation gas turbine engines typically utilize twin-orifice swirl atomizers to achieve a fine spray, widen the spray cone angle, and shorten spray penetration. However, using twin-orifice atomizers complicates the spray structure, and knowledge of the spray, especially in the near-field nozzle zone, remains limited. This study experimentally investigates the morphologies and structure of liquid fragments in the near-field nozzle of a twin-orifice atomizer. A high-speed backlit experimental system was developed to examine the liquid fragment morphologies and structures. The fragments are classified into spherical droplets, ligaments, and other irregular structural fragments. Results show that with increasing the pressure in the near field of the nozzle, the proportion of nearly round fragments decreases with increasing pressure. In contrast, the proportion of ligament-like fragments tends to increase. Besides, the particle size distribution did not change significantly within the 10 to 50-bar pressure range. Understanding these morphologies and structures could aid in developing a secondary atomization model suitable for predicting the droplet size distribution generated by twin-orifice atomizers.