基于RBF代理优化的固体火箭发动机喷管型面设计

Nozzle profile design of solid rocket motor based on RBF proxy optimization

针对固定扩张比与扩张段长度的二维轴对称固体火箭发动机喷管进行扩张段型面优化,优化目标为喷管推力最大化,优化参数为贝塞尔曲线控制点的径向位置,优化方法采用径向基函数(Radial Basis Function, RBF)代理优化算法。采用纯气相与两相流两种模型分别进行优化设计,纯气相的结果表明,对于10个控制点表达的贝塞尔曲线,优化后的推力提高了1.64%。以此优化型面为初始型面,增加控制点个数至16个,二次优化后的推力又提高了0.095%。增大优化参数范围,同时引入判断拐点的约束,对于10个控制点表达的贝塞尔曲线进行单轮优化,结果同上述经过两轮优化之后的结果相近,优化后的喷管推力提高了1.78%,说明算法具有较强的稳定性。通过对不同控制参数个数的贝塞尔曲线优化过程的对比,给出了合理选择控制点个数的方法与建议。两相流的优化结果表明,由于颗粒的滞后影响造成了两相流损失,两相流喷管的推力小于纯气相喷管,但两相流喷管优化后的推力较优化前初始型面的推力提高了1.87%,略高于纯气相喷管。RBF代理优化算法适用于由任意数量控制点组成的贝塞尔曲线表达的喷管扩张段型面优化,并有较高的效率与较强的稳定性。

The divergent section profile of two-dimensional axisymmetric solid rocket motor nozzles with a fixed divergent ratio and divergent section length,was optimized to maximize nozzle thrust.The optimization parameters included the radial position of the control points on the Bezier curve,and the RBF proxy optimization algorithm was employed as the optimization method.The two models of pure gas phase and two-phase flow were used to optimize the design respectively.The pure gas phase results show that the optimized thrust is increased by 1.64%for the Bezier curve expressed by 10 control points.With this optimized surface as the initial surface,the number of control points is increased to 16,and the thrust after secondary optimization is increased by 0.095%.Expanding the range of optimization parameters and introducing constraints to judging inflection points,the single-round optimization of Bezier curve expressed by 10 control points was carried out.The results were similar to the above results after two rounds of optimization.The optimized nozzle thrust was increased by 1.78%,which demonstrates the algorithm's strong stability.By comparing the optimization process of Bezier curve with different number of control parameters,the method and suggestion for reasonably selecting the number of control points were given.The optimization results of two-phase flow show that the thrust of two-phase flow nozzle is smaller than that of pure gas phase nozzle due to two-phase flow loss resulting from the particle lag effect.However,the thrust of two-phase flow nozzle after optimization is 1.87%higher than that of the initial surface before optimization,and the increase proportion of thrust is slightly higher than that of pure gas phase nozzle.The RBF surrogate optimization algorithm is suitable for the optimization of nozzle divergent section surface for Bezier curve expressed by any number of control points,which has high efficiency and strong stability.