Abstract: To investigate the heat transfer characteristics of impinging jet flow and annular recirculation in a swirl nozzle anti-icing system for engine inlet, a numerical simulation method is conducted to analyze the coupled internal-external flow and heat transfer within the anti-icing cavity. Characteristic parameters, namely Nozzle Spray Angle, Nozzle position and Nozzle area ratio, are established for evaluating anti-icing performance. The influence of these parameters on temperature distribution and thermal uniformity at the inlet lip are systematically investigated. A quantitative correlation is derived between the average Re and the average Nu for the anti-icing flow. Results show that: Increasing the standoff distance between the nozzle and the inlet lip enhances anti-icing effectiveness. Changing Nozzle Spray Angle and Nozzle Position slightly offset toward the inner side of the inlet significantly improve temperature uniformity. Increasing the area of the orifice adjacent to the inlet improves temperature uniformity but simultaneously raises the risk of overheating. These findings provide a mechanistic basis for optimization of swirl nozzle anti-icing systems.

Key words: Engine inlet, Swirl nozzle, Anti-icing system, Heat transfer characteristics, Impinging jet, Annular flow