Design of Thrust-Optimized Scramjet Nozzle and Its Concise Estimation Method

This Paper is a computational investigation of a scramjet nozzle design based on maximum thrust theory and its feasibility analysis. A new design method for a two-dimensional complete thrust-optimized single expansion ramp nozzle under aerodynamic constraints by applying the method of characteristics is proposed. The carefully chosen verification and validation benchmarks confirm the accuracy, effectiveness, and superiority of the current method. Results indicate that the introduced design method has comprehensive advantages over the traditional approach under design/off-design conditions. Specifically, the maximum increase in axial thrust reaches 6.38%, and the maximum increase in lift exceeds 180%. Necessary conditions of the thrust-optimized nozzle design are deduced combining Prandtl–Meyer relation and corner conditions, which provides a direct judgment criterion for the rationality of initial design conditions, and leads to a concise dimension estimation method. Relative errors of no more than 5% demonstrate the credibility of this approach through a comparison with the theoretical solutions. The refined structure topology of the thrust-optimized single expansion ramp nozzle further reveals the equivalent relations between the aerodynamic and geometric design conditions based on the estimation results.