基于驻定斜爆轰波组织燃烧的推进概念近年来发展迅速，研究规模持续扩大，受到广泛关注，这种斜爆轰发动机充分利用爆轰燃烧循环效率高、放热速率快的特点，兼具构型简单、燃烧稳定等优势，为高超声速吸气式推进提供了一种有潜力的解决方案。针对斜爆轰发动机的高马赫数巡航状态，大量数值研究揭示了斜爆轰起爆、驻定和发展规律，采用氢气、煤油等燃料的斜爆轰发动机风洞试验验证了其技术可行性。在实际飞行任务中，吸气式冲压发动机在达到巡航状态之前一般需要经历起动和加速阶段，其中存在一些关键科学问题，值得深入研究，但目前相关研究较少。

本文首先在JF-12风洞斜爆轰发动机系列实验的基础上，利用吸收光谱技术对发动机进行燃烧诊断，在前导激波附近测量OH自由基分压以验证发动机模型的爆轰燃烧模式，这部分工作是对驻定斜爆轰推进概念验证系列成果的补充和强化。随后，面向斜爆轰发动机的进一步工程化，本文分析论证了发动机起动和宽域飞行中的两个关键问题：低马赫数起爆问题和宽速域燃烧性能问题。目前广泛研究的固定斜劈构型通常诱导过驱动斜爆轰波，其过驱动度与来流条件相关，而不受壁面条件影响的自由斜爆轰波过驱动度始终为1，来流状态变化时爆轰燃烧保持在Chapman-Jouguet状态，具有很强的自适应特性。特别地，如果采用有源起爆方式代替斜劈起爆，能够有效解除起爆能量对来流动能的依赖关系，实现低马赫数起爆，同时形成自由斜爆轰波。根据上述研究内容，本文取得的主要创新成果如下：

(1) 在激波风洞自由射流实验中，利用吸收光谱获得了发动机的燃烧反应面信息，验证了发动机模型的爆轰燃烧模式，实验结果还验证了可调谐激光二极管吸收光谱技术在高超声速、高焓风洞试验中应用的可行性。

(2) 提出了爆轰一维与二维传播的时空关联特性，阐明了正爆轰与斜爆轰在起爆、传播等基础问题上的内在关联，该特性还可用于辅助发动机燃烧室构型设计。

(3) 基于时空关联特性和一维自由爆轰的起爆规律，获得了自由斜爆轰的形成条件，揭示了自由斜爆轰具有宽速域稳定燃烧特性。

(4) 建立了有源起爆的物理模型，推导了临界起爆能量随来流马赫数的线性变化关系，并进行了数值验证，这一规律为低马赫数下有源起爆的设计思路提供了理论依据。

The propulsion concept based on standing oblique detonation-wave-organized combustion has developed rapidly in recent years. The research team continuous to expand and the project attracts more and more attentions. The standing oblique detonation ramjet, also referred to as oblique detonation engine, takes advantages of high thermal cycle efficiencies and high energy release rate of detonation combustion mode. Meanwhile, it also benefits from simple configurations and relative stable combustion states. A large number of numerical simulations have revealed the ignition, stabilization and propagation behavior of oblique detonation waves during high Mach number cruise. The recent shock tunnel experiments over an engine prototype employing hydrogen or kerosene fuels have demonstrated the feasibility of the oblique detonation engine techniques. In actual flight missions, the air-breathing ramjet generally needs to undergo the start-up and acceleration stages before reaching the cruise state, which contains some key scientific issues. However, studies are still lacking to deal with ignition and thrust problems at these off-design points.

In the present work, experiments of combustion diagnostics based on freejet tests in JF-12 shock tunnel are presented at first. Absorption spectroscopy techniques were employed to detect OH radicals near the leading shock wave in the engine combustor. The experiments were designed to further verified the detonation combustion mode of the engine prototype, which serves as a supplement and enhancement to concept verifications of standing oblique detonation propulsion. Aiming at the further engineering applications of oblique detonation engines, two key issues, namely low Mach number ignition and combustion performance in wide range flight, are figured out during engine start and acceleration process. The widely studied fixed wedge configurations generally induced over-dirven oblique detonation waves, whose over-driven degree depends on inflow properties. While free oblique detonation waves could maintain Chapman-Jouguet state under varying inflow conditions. The adaptive feature makes them suitable to be applied in wide range flights. Specifically, if non-invasive energy depositon methods, instead of wall compressions, are employed to induce free oblique detonation waves, the dependence of effective ignition energy on inflow kinetic energy can be released to realize low Mach number ignitions. In detail, the primary innovations of this thesis are presented below:

(1) In shock tunnel freejet tests, the position and thickness of reaction zone were revealed through absorption spectroscopy measurements. The relative position of shock front and reaction zone further verified the detonation combustion mode in the engine prototype. Moreover, it was also proved that tunable diode laser absorption spectroscopy devices can be applied in the harsh environment of hypersonic, high-enthalpy shock tunnel tests.

(2) The space-time correlation between one- and two- dimensional detonation propagation was proposed, which clarified the internal relations of normal and oblique detonation on basic issues, such as ignition and wave propagation. The space-time transition can also be used to develop a design tool of engine combustor.

(3) The free oblique detonation concept was verified numerically and studied systematically. The adaptive feature of free oblique detonation waves was indicated by numerical results, which helps improve the engine performance during wide range flights.

(4) A physical model of active ignition through non-invasive heat sources was proposed and verified. A linear relation between the effective ignition energy and inflow Mach number was derived from the model. The results implied that low Mach number condition is beneficial to active ignition, which provided a theoretical basis for the active ignition design under low Mach numbers.