凹面腔内环形超声速射流聚心碰撞的激波聚焦起爆爆震机理研究

2-Stage pulse detonation engine has been proposed to work with high operating frequencies, no special ignition system,which attract many countries.But mechanism of detonation initiation via shock wave focusing has not been broken through, which restrict its engineering application. In this study, schlieren apparatus, PIV, 3-D numerical simulation will be applied. The detonation initiation mechanism of shock wave focusing by imploding annular supersonic jets in a cavity will be researched. This project investigate on controlling means and mechanism of forming nonsteady shock wave by supersonic jets imploding, shock wave focusing, describing and controlling methods of detonation initiation by shock wave focusing, mechanism of detonation wave reversed propagation through annular jets channel.The principle of coupling jets imploding, shock wave reflection, shock wave focusing and detonation initiation will be elucidated. Unsteady interactional effect between cavity and annular jets channel will be understanded. Means of backfire restraining and back transmittal pressure controlling will be acquired. The mechanism of detonation initiation via shock wave focusing and experimental methods will be innovated. Investigations on this project can improve the theory of combustion and detonation, and provide a scientific basis for detonation propulsion design.

两级脉冲爆震发动机（2-Stage PDE，一级等压燃烧，二级爆震燃烧）因爆震循环频率高、无需专门的点火起爆系统等优点，引起了各国的高度重视。但到目前为止二级爆震燃烧的凹面腔内，激波聚焦诱导起爆爆震的机理尚不十分清楚，成为制约2-Stage PDE设计及工程应用的瓶颈。本项目拟采用纹影仪观测、PIV测试、三维高精度数值模拟，进行激波聚焦诱导起爆爆震的机理研究。研究内容包括：超声速射流聚心碰撞产生非定常激波与激波反射、聚焦的机理及控制方法；激波聚焦起爆爆震过程的数值模拟与机理分析；爆震波向环形射流入射通道的反传特性及抑制方法。通过本项目的研究，揭示环形超声速射流在凹面腔内聚心碰撞、激波产生、反射聚焦、起爆爆震、实现激波聚焦诱导起爆爆震机理和实验实现方法的原始创新。研究结果可进一步丰富爆震燃烧理论，并为激波聚焦起爆的脉冲爆震发动机设计提供技术储备，具有十分重要的科学意义。

项目紧紧围绕3个关键科学问题开展研究，即，环形射流聚心碰撞产生激波、反射聚焦的机理及控制方法；激波聚焦起爆爆震细观演变过程的描述；爆震反传特性和抑制反传、减小反压的控制方法。已按项目计划完成相应研究工作，在此基础上，发展了新型激波聚焦起爆模型。此外，有一些重要的研究结果：（1）连续两相流激波聚焦起爆实验表明，虽然能够实现多循环的激波聚焦点火，但循环频率低（8Hz），峰值压力小（0.4MPa），当环形射流出口压力略低于环形射流喷口上游压力时，就会形成聚心碰撞的气幕，从而封闭了凹面腔底部废气的排出，从而造成射流强度和激波强度较弱，不能形成高频循环起爆；（2）数值模拟了周向均布的若干微激波管产生激波或热射流起爆爆震波过程，结果表明，这种新型的起爆模型，能够可靠起爆爆震；（3）关于爆震反传问题，可以采用分隔入射通道入射的非预混燃气射流形成方式，抑制爆震反传，但对于压力的反传，还需要做更深入的研究；（4）需要测量连续两相流激波聚焦起爆原理样机推力，评估射流聚心碰撞的燃烧效率，验证能否实现增推和降低燃油消耗，对标强化加力燃烧室燃烧的应用。项目研究结果为脉冲爆震发动机研究提供了理论和实验参考。