Influence of directed flow nozzle swirl enhancer on heat transfer at engine lip

To address the anti-icing issue of the lip of a high-bypass-ratio turbofan engine, a numerical simulation method is employed to compare and analyze the heating performance of two bleed air anti-icing methods: the Directed Flow Nozzle Swirl Enhancer (DFNSE) and the traditional piccolo tube. The influence of key geometric parameters of DFNSE (twist angle, number of flow passage, and contraction-expansion ratio of the annular flow passage) on anti-icing effects is systematically investigated. The results indicate that, under identical bleed air conditions, the DFNSE exhibits a higher average temperature on the outer skin, lower bleed air pressure and less heat accumulation, compared to the piccolo tube, resulting in a lesser impact on engine performance. Through investigation of heat transfer effects under varying structural parameters, it is found that the twist angle, number of flow passage, and contraction-expansion ratio have significant nonlinear effects on heating uniformity and system energy consumption. An optimal combination exists, enabling both efficient heating and low-energy-consumption operation. Furthermore, the study proposes a comprehensive evaluation metric, the “heating quality coefficient”, which confirms that the DFNSE outperforms the traditional piccolo tube in terms of heating efficiency, temperature uniformity, and system economy. This coefficient provides a quantitative indicator for the performance evaluation of the anti-icing system. The research conclusions can serve as a theoretical basis and engineering guidance for the optimal design of the aero-engine lip anti-icing system