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.