Investigation On Aerodynamic And Stealth Characteristics Of Aeroengine Nozzle

At present,the common detection methods for fighters are radar detection and infrared detection.The engine exhaust system is not only the main infrared radiation source of the fighter,as a cavity structure,but also an important radar scattering source for fighter.Therefore,it is an important issue on how to reduce the infrared radiation and radar signal strength of the exhaust system in the design of stealth fighter.Under this background,a study was conducted on infrared and radar stealth performance of tailpipe nozzles of fighter engines.Firstly,based on the nozzle design theory,the procedure of obtaining nozzle profile parameters was designed.Axisymmetric nozzle,two-dimensional nozzle,different S-shaped two-dimensional nozzles possessing 5 centerline variations and 3 cross-sectional area variations were designed based on the same basic parameters in this study.Secondly,based on the designed model,aerodynamic performance and temperature field of different nozzle models were obtained by CFD numerical simulation.The aerodynamic characteristics and infrared stealth performances of axisymmetric nozzle,two-dimensional nozzle and S-shaped two-dimensional nozzle were compared and analyzed combining with the aerodynamic theory and infrared radiation theory.The influence of the variation of the centerline on the aerodynamic characteristics and infrared stealth performance of S-shaped twodimensional nozzle was investigated.The backward radar cross section(RCS)of the nozzle was calculated by the method of the multi-layer fast multipole method(MLFMM),obtaining the backward radar cross section of nozzles.The radar stealth performances of axisymmetric nozzle,two-dimensional nozzle and S-shaped two-dimensional nozzle were compared and analyzed.The influence of the centerline variation regulation and the variation of the crosssectional area on the radar stealth performance of the S-shaped two-dimensional nozzle.Finally,the comprehensive stealth performance of each nozzle was analyzed combined with the infrared and radar stealth performances.The results show that the comprehensive stealth performance of single S-shaped two-dimensional nozzle is greatly improved compared with the two-dimensional nozzle and axisymmetric nozzle.Compared with the axisymmetric nozzle,the length of the wake high temperature core of the two-dimensional nozzle was shortened by more than 50%,improving the infrared stealth performance.Adopting the centerline distribution of "beginning and end the same" and area distribution of "beginning and end the same" in the single S-shaped two-dimensional nozzle designs lead to both good aerodynamic and stealth performances,providing reference for the design of stealth nozzle.