高超声速飞行器在向更高马赫数和更强机动性发展，基于爆燃燃烧的传统动力技术难以满足这一需求。利用斜爆轰波进行燃烧组织的斜爆轰发动机因具有能量转换迅速、热循环效率高、飞行速域宽广等特点而引起越来越多的关注，是高超声速推进技术的前沿领域。研究人员借助近年来发展的计算流体力学方法，结合有限的实验结果和理论分析，在斜爆轰的流动与燃烧机理认识方面取得了进展。但目前斜爆轰发动机仍处于实验室研制状态，其工程化应用过程中需要关键基础科学理论的支撑。

   激波与化学反应的强耦合作用导致爆轰波本身具有极强的不稳定性特征，保证斜爆轰波在发动机燃烧室内稳定燃烧是其工程应用的关键。这涉及到两个关键问题：一是斜爆轰的起爆波系的稳定性特征；二是外界扰动作用下爆轰波面的燃烧组织。前者直接决定斜爆轰能否在燃烧室内驻定，后者则直接影响发动机的推进性能。本文面向斜爆轰波在高超声速推进系统中的应用，针对斜爆轰发动机所涉及到的关键流体力学问题，研究斜爆轰波的起爆结构的失稳特性和波面动态特征，相关的研究成果将为斜爆轰发动机燃烧室的设计和斜爆轰波的调控提供科学依据。主要研究内容和创新性成果如下：

1. 针对斜爆轰波起爆结构的多样性，通过引入气动参数、几何参数和化学参数来量化不同因素对起爆波系的影响，发现斜爆轰波起爆结构失稳后伴随着无规则、无衰减的振荡。通过分析爆轰内在失稳特性和化学反应敏感性之间的联系，确认起爆初始阶段形成的强解是低马赫数下斜爆轰起爆结构失稳的关键物理机制。
2. 针对起爆初始阶段斜爆轰局部流动的非均匀特性，重点分析起爆区附近强解形成的机理，提出关键特征参数来刻画斜爆轰波局部流动的化学非平衡特征，并结合爆轰极曲线理论建立斜爆轰起爆长度、起爆区波系类型的量化判据。
3. 针对斜爆轰波面胞格的失稳特性，通过引入功率谱密度分析方法，对波面压力时序信号的频谱特征进行分析，获得波面失稳的两种物理机制，揭示定常来流中斜激波与燃烧的耦合机理。
4. 针对强迫扰动作用下斜爆轰的波面动力学特征，通过监测波面位置的振荡信号并分析其频率特性，获得外界扰动对波面燃烧的作用规律，揭示强迫扰动作用下波面小尺度波系的演化机理。

    Hypersonic aircraft is developing toward a higher Mach number and super maneuverability, but the traditional propulsion system based on deflagration combustion is hard to satisfy the requirements. The oblique detonation engine (ODE) has the characteristics of rapid energy conversion, high thermodynamic cycle efficiency, and wide flight speed range, which has attracted increasing attention. An oblique detonation wave (ODW) in an ODE combustor is used to burn fuels under a hypersonic inflow. The ODE is one of the developing research fields in air-breathing hypersonic propulsion technology. With the development of computational fluid dynamics, researchers have made significant progress in recent years. Deeper insight into the flow and combustion mechanism of oblique detonation combustion is obtained by combining with the limited experimental results. However, the ODE is still in the early stages and the practical utility of ODW is a big challenge for a brief spell. The basic scientific theory plays a supporting role in the engineering application of ODE.  

    Since the strong coupling of shock wave and chemical reaction, detonation combustion is a natural instability entity. The standing of oblique detonation in a combustor is the principal determinant of ODE. There exist two key scientific problems. The first one is the morphology and stable features of the ODW initiation zone and the other one is the dynamic features of detonation front. The former is closely associated with the standing of an oblique detonation in a combustion chamber, and the latter has a huge effect on the propulsion performance of the ODE. Considering the application of oblique detonation waves in the hypersonic propulsion system, we focus on the key fluid mechanics of ODE. The instability characteristics of initiation wave systems and dynamic features of the wavefront are studied in this paper. The related research results could not only provide a scientific basis for the design of the combustion chamber but also provide insight into physical mechanism of detonation combustion. The main research contents and innovative results are summarized as:

1. Aiming at the diversity of ODW initiation structures, the initiation wave complex is thoroughly investigated by varying aerodynamic parameters, geometric parameters and chemical parameters. The initiation structure instability results in the irregular oscillation of wave system. By analyzing the relationship between inherent instability and chemical reaction sensitivity, it is confirmed that the presence of the strong solution is the key mechanism for the instability of ODW initiation structure at a low Mach number.
2. Aiming at the non-uniform flow of local upstream detonation wave behind the initiation point, the formation mechanism of strong solution near the initiation zone is analyzed systemically. The characteristic parameters are proposed to describe the coupling characteristics of flow and heat release. Combined with the detonation polar theory, the quantitative criteria of initiation length and transition type of ODW are established and verified.
3. To obtain the instability of ODW cellular surface, the timing signals of detonation front pressure are collected and analyzed using the power spectral density (PSD) method. The frequency spectrum characteristics give two types of oscillating modes corresponding to two instability mechanisms of wave surface. One is originated from the evolution of small disturbance, and the other one is triggered by the un-uniform flow of initiation zone.
4. To solve the wave surface dynamic behaviors of ODW under forced disturbance, the oscillation characteristics and frequency spectrum of ODW surface position are systemically investigated. The unsteady flow and combustion are analyzed, and the evolution mechanism of small-scale wave complex on wave surface under forced disturbance is discussed.