Single- and Multi-Objective Optimization of Scramjet Components Using Genetic Algorithms Based on a Parabolized Navier-Stokes Solver

Abstract

A 2D hypersonic inlet which can self-start at relay Mach number (Ma=3.5) is designed. Then single- or multi-objective optimization designs of the 2D inlet are carried out on cruise operation point (Ma=7.0) by Sequential Quadratic Programming (SQP), Multi-Island Genetic Algorithm (MIGA), and Multi-Objective Genetic Algorithms (MOGAs), i.e. Neighborhood Cultivation Genetic Algorithm (NCGA) and Nondominated Sorting Genetic Algorithm II (NSGA-II). In these optimizations, the inlet flowfields are calculated with the Single-Sweep Parabolized Navier-Stokes (SSPNS) algorithm codes which are proved highly accurate, highly efficient for supersonic/hypersonic flowfield simulations previously. Singleobjective optimization results show that pressure recovery maximum model is better than effective kinetic energy coefficient maximum model. Multi-objective optimization results reveal the tradeoffs among total pressure recovery, static pressure rise, and drag coefficients. Based on multi-objective design process, a multi-operation-point design and a design point determi-nation process are investigated. Results show if design point is set at cruise point, the off-design operation mass capture coefficients is relatively low; whereas if the design Mach number is 6.5, the 2D inlet will get good overall operation performances along the constant dynamic trajectory. The same optimization design methods are applied to design several 2D Single-Expansion-Ramp Nozzles (SERNs). Result of the single-objective optimization design shows that the objective, i.e. the thrust coefficient, is improved, but the corresponding lift coefficient is relatively low. In the 2- and 3-objective cases, tradeoffs of the thrust coefficient, the lift coefficient and the pitching moment coefficient, are obtained. Results show that cowl length and initial expansion angle of ramp influence the SERNs performance significantly. It is also shown that the shorter the cowl is, the higher the lift is; whereas the larger the initial expansion angle is, the smaller the pitching momentum is.