Inverse Design Method on Scramjet Nozzle with Full Geometrical Constraints for Nozzle-Afterbody Integration

A design method on scramjet nozzles is proposed to satisfy the requirements of nozzle positions and geometrical constraints. The proposed method adopts the inverse design concept and maximum thrust theory to achieve a good aerodynamic performance. The nozzle contours are generated by a universal method for solving partial differential equations: the method of characteristics. First, the principle of the proposed method is discussed, including the details of the implementation procedure. Second, the numerical simulation method adopted to obtain the flow field of the nozzle is briefly introduced. Then, the verification cases are conducted to validate the accuracy and effectiveness of the proposed method by comparing the flow conditions on two key points. The maximum relative error of the Mach number is only -0.50%. The flow deflection angle exhibits a relatively more significant deviation than the Mach number, reaching approximately -1.46%. Overall, the proposed method can design the required nozzle with sufficient accuracy. Subsequently, the nozzle's geometrical parameters in a previous study are adopted to design the nozzle using the proposed method. The aerodynamic performance, especially in the axial thrust coefficient, remains approximately constant. The comparison of the aerodynamic performance shows that the proposed method not only satisfies the requirement of high aerodynamic performance but also realizes the full geometrical constraints. This study provides an effective nozzle design method with high aerodynamic performance and full geometrical constraints, which can facilitate the airframe-engine integration. (C) 2021 American Society of Civil Engineers.