Effects of unsteady oblique shock wave on mixing efficiency of two-dimensional supersonic mixing layer
Effects of unsteady oblique shock wave on mixing efficiency of two-dimensional supersonic mixing layer
复制标题
非定常斜激波对二维超声速混合层混合效率的影响
DOI：
10.1016/j.actaastro.2020.07.028
复制
发表时间：
2021
影响因子：
3.5
通讯作者：
Kun Ye
中科院分区：
文献类型：
--
作者：
Zhangming Zha;Zhengyin Ye;Zheng Hong;Kun Ye
超燃冲压发动机是未来实现长航时和超声速飞行的关键技术。随着空气在几毫秒内通过超燃冲压发动机内部，燃料和空气的快速混合成为发动机设计的巨大挑战之一。在各种改善燃料-空气混合的方法中，激波增强是一种有效的技术手段。在此基础上，提出了一种利用非定常激波提高超声速混合层混合效率的新方法。通过比较无激波混合层、定常激波/混合层相互作用和非定常激波/混合层相互作用对混合层混合效率的影响，验证了该方法的可行性。比较了三种工况下的激波结构和涡结构，计算了涡度和湍流强度。结果表明，激波对混合层有显著影响，尤其是非定常激波。非定常激波会引起激波结构和主流流动方向的周期性变化。激波会增加相互作用点处的平均涡量，非定常激波会大大促进涡结构的演化。流场的周期性变化会引起混合层的振荡，导致平均涡度及其垂直分布的波动范围增大。此外，非定常激波可以显著增加混合层的湍流强度，振荡对湍流强度的贡献将抵消激波压缩效应带来的减少。综上所述，非定常激波能更有效地提高混合效率。
Scramjet is the key technology to achieve long-endurance and supersonic flight in the future. With air flowing through the interior of a Scramjet in milliseconds, the rapid mixing of fuel and air becomes one of the great challenges of engine design. Among the various methods of improving fuel-air mixing, shock wave enhancement is an effective technical approach. Based on this, a new method is proposed in this paper to enhance the mixing efficiency of the supersonic mixing layer by using unsteady shock wave. The feasibility of the method is verified by comparing the effects of three conditions on the mixing efficiency of the mixing layer, which are shock-free mixing layer, steady shock/mixing layer interaction, and unsteady shock/mixing layer interaction. The shock wave structures and vortex structures in the three conditions are compared and the vorticity and turbulence intensity are calculated. The results indicate that the shock waves have a significant effect on the mixing layer, especially the unsteady shock. The unsteady shock will cause periodic changes in the shock wave structures and the direction of mainstream flow. Moreover, the shock waves will increase the averaged vorticity at the interaction point and the unsteady shock can greatly enhance the evolution of the vortex structures. The periodic changes of the flow field will cause the oscillation of the mixing layer, resulting in an increase in the averaged vorticity and its fluctuation range of vertical distribution. Furthermore, the unsteady shock wave can significantly increase the turbulence intensity of the mixing layer, and the contribution of the oscillation to the turbulence intensity will counteract the reduction caused by the compression effect of the shock wave. In conclusion, the unsteady shock waves can enhance the mixing efficiency more effectively.