超声速气流中微型涡流器诱导下的燃料射流流场设计优化与混合增强机理研究

The interactional mechanism between the fuel injection, the wave system and the vortex structure induced by the vortex generator has a great impact on the mixing augmentation process in scramjet engines. The fuel injection mixing enhancement mechanism induced by the vortex generator in supersonic flows has been investigated by the hybrid LES/RANS method and the NPLS technique, and the influences of the geometrical parameters of the vortex generator and the fuel injector configuration on the mixing process have been analyzed as well. Then, the important factors which affect the mixing efficiency between the fuel and the supersonic airflow have been obtained. Based on the researches mentioned above, the fuel injection flow field induced by the vortex generator has been optimized and explored by the multiobjective dynamical particle swarm optimization algorithm based on the Kriging surrogate model and the self-organizing mapping neural network. At last, the interactional mechanism between the shock wave train, the separation flow and the fuel injection with the high back pressure has been investigated by the hybrid LES/RANS approach and the high speed schlieren photography technique, and this is very important for the investigation of the jet mixing properties under the combustion condition.

涡流发生器诱导下的波系与漩涡结构和燃料射流之间的交互作用机制在超声速燃烧中能起到混合增强作用。结合混合LES/RANS数值模拟方法和NPLS实验技术研究超声速气流中涡流发生器诱导下的燃料射流混合增强机理，探索涡流发生器结构参数和燃料喷孔形状对混合过程的影响，分析影响燃料与超声速来流之间混合效率的关键因素。在此基础上，结合基于Kriging代理模型的多目标动态粒子群优化算法和自组织映射神经网络实现对涡流发生器诱导下的燃料射流流场设计优化与数据挖掘。最后，结合混合LES/RANS数值模拟方法和高速纹影实验技术研究高反压下激波串与分离流动和燃料射流的相互作用机制，这对研究燃烧状态下的射流混合特性具有十分重要的意义。

采用数值模拟方法探究了微小斜坡对超声速横向射流流场性能的影响，分析了微小斜坡高度以及氢气喷孔喷注压比对混合效率、燃料穿透深度以及总压损失的影响。基于此结果，提出采用激励射流和微小斜坡耦合来进一步提高超声速横向射流流场的混合性能。结果表明，氢气喷孔喷注压比周期性变化的横向射流流场，其综合性能更优，实现了混合效率和燃料穿透深度的同时提高。进一步，提出了燃料喷孔和空气喷孔串联的双孔喷注系统，主要是探究空气喷孔及其长宽比对超声速横向射流流场的影响，发现当空气喷孔长宽比足够大时，不仅可以增强燃料与空气的混合，还能提高燃料穿透深度，但是不可避免地带来比单孔射流更大的总压损失。紧接着，采用极差分析法深入探究了带有微小斜坡涡流发生器的横向射流流场信息，分别以最短混合长度、最大穿透深度、最小总压损失为优化目标得到了三个优化微小斜坡构型，而且三个优化模型的流场性能得到数值仿真验证，并提出空气射流和微小斜坡耦合的喷注策略以综合空气射流与微小斜坡各自的优势，最终得到了总压损失较小、混合长度更短以及穿透深度比较理想的超声速横向射流流场。以NPLS技术和SPIV技术为主要实验观测手段，通过研究射流CVP发展过程发现，VG尾迹中的流向涡加快了射流CVP的发展速度，同时也加快了其耗散速度，射流CVP的速度环量先增大后减小，没有出现保持不变的阶段，这对促进射流与周围流体的混合有重要影响，同时由于VG与喷孔相对位置的不同，其尾迹与射流的相互作用机制不同，VG距离喷孔较近时可以有效增强近场混合区域羽流的穿透深度和横向扩散，而距离喷孔较远时射流穿透深度有较大提高，横向扩散反而受到抑制。此外通过对VG构型参数、VG位置和射流/来流动压比等参数进行优化设计，射流穿透深度存在最优值。