基于遗传算法和空间推进方法的单壁扩张喷管优化设计研究

 将单目标遗传算法和多目标遗传算法（包括NSGA-II和NCGA），与高效、高精度的空间推进流场数值模拟方法——SSPNS方法相结合，对二维超燃冲压发动机尾喷管即单壁扩张喷管（SERN）进行了气动优化设计研究。在巡航点（Ma=6.0）讨论了推力系数C_T最大单目标模型，推力系数C_T最大升力系数C_L最大两目标模型，以及推力系数C_T最大升力系数C_L最大俯仰力矩系数C_m最小三目标模型，分别得到了喷管的最大推力设计和关于多个目标性能的Pareto最优前沿。结果表明，扩张壁初始扩张角θ_r,i和外罩长度L_c对C_T影响较大；较小的L_c和较大的θ_r,i设计，将降低外罩内表面的负升力作用而使得SERN的C_L较大；较长外罩和较小的θ_r,i，对应Pareto最优设计的C_M较小。

Optimization Design of Single-expansion-ramp Nozzles Using Genetic Algorithms Based on a Parabolized Navier-Stokes Solver

The single-and multi-objective optimization designs of several 2D single-expansion-ramp nozzles(SERNs)are carried out by single-objective genetic algorithm(GA)and multi-objective GAs(including NCGA and NSGA-II).In these optimization design processes,the SERN flowfields are calculated with SSPNS(single-sweep Parabolized Navier-Stokes algorithm)codes which are proved highly accurate and highly efficient for supersonic/hypersonic flowfield simulations.The single-objective optimization design results show that the objective(i.e.thrust coefficient)is improved,but the lift coefficient is too low.In the 2-and 3-objective optimization designs,Pareto optimum fronts of thrust coefficient,lift coefficient and pitching moment coefficient are obtained.Results show that the cowl length and initial expansion angle of the ramp influence the SERNs performance significantly.It is also shown that the shorter the cowl is,the higher the lift coefficient is,and the larger the initial expansion angle is,the smaller the pitching momentum is.