Inverse design methodology on a single expansion ramp nozzle for scramjets

An inverse design method on a single expansion ramp nozzle (SERN) is proposed in order to obtain good aerodynamic performance and full integration with airframes. By using this method, the flow parameters along the nozzle outlet and the shape of the outlet can be specified in advance. The details of the proposed method are introduced in this paper. Method of characteristics (MOC), known as a universal mathematical method, is the kernel of the design method and applied to generate the nozzle contour inversely. Also, the computational fluid dynamic (CFD) approaches are used to verify the effectiveness and accuracy of the proposed method. In the verification case, the relative error of the Mach number on the nozzle outlet in the main region is less than 0.2%. Then, an actual design case on SERN is performed using the proposed method. Two SERNs (SERN A1 and SERN A2) are designed using the conventional design method to examine the superiority of the proposed method. The comparison of the aerodynamic performance shows that the nozzle designed by the proposed method gains approximately 6.3% and 26.2% increments in axial thrust coefficient relative to SERN A1 and SERN A2 on the design condition, respectively. The improvement in the lift of the SERN designed by the proposed method is over 200% on the design condition. Besides that, findings also indicate that the proposed design method can offer a considerable improvement in the thrust coefficient and lift on the off-design conditions. In conclusion, the study can provide a powerful design method for SERNs.