Optimization of a gas–liquid nozzle using computational fluid dynamics and response surface method for enhancing impingement characteristics

A novel gas–liquid nozzle is designed to address the limited energy efficiency of single-phase jet impingement systems. By leveraging the pressure drop generated in the nozzle converging section, the design facilitates gas injection to form a gas–liquid jet that enhances impingement performance. However, the geometric influence of the gas–liquid nozzle and the resulting water film characteristics upon impingement remain unclear. In this study, three-dimensional computational fluid dynamics (CFD) simulations were conducted on the circular water film (CWF) generated by a gas–liquid jet. The influence of key nozzle parameters on stagnation pressure was analyzed using the response surface method, revealing that the nozzle contraction radius is the dominant factor. High-speed imaging and jet impact force experiments were conducted to validate the performance of the optimized nozzle. The results show that the regression model, using stagnation pressure as the response variable, illustrates excellent predictive accuracy. Compared with the original design, the optimized nozzle consistently produced a larger water film area and a superior impingement performance due to the formation of internal air bubbles within the film. Moreover, the optimized nozzle demonstrated a consistently higher jet impact force coefficient than the original nozzle under all tested conditions. This work presents a novel gas–liquid nozzle design and a systematic optimization framework grounded in the analysis of circular water film characteristics.