Abstract The Rocket-based Combined-cycle (RBCC) engine is regarded as one of the most efficient propulsion systems for reusable space transportation vehicles and hypersonic cruise vehicles. It can perform excellently over a very broad range of Mach numbers and flight altitudes through multi-mode operations by effectively integrating the high thrust-to-weight ratio of the rocket engine and the high specific impulse of the airbreathing engine. As one of the most distinctive features and advantages of an RBCC engine, the ejector mode is an important mode for supporting the flight vehicle's rapid acceleration and climb. The engine performance, especially the specific impulse in the ejector mode, plays a vital role in determining the majority of the total fuel consumption, the propulsion efficiency of the entire RBCC engine, and further the whole flight trajectory. Therefore, an excellent performance in the ejector mode sufficiently guarantees the competitiveness and application prospect of an RBCC engine. This paper presents a comprehensive and systematic review of the research progress on the ejector mode of RBCC engines in different countries and different historical periods. In the survey, the summary delivers a progress overview on the ejector mode research, which covers a wealth of landmark experimental and application results on the ejector mode research in different historical periods. On this basis, a number of relevant key technologies regarding the study of the ejector mode are proposed, including efficient ejection, efficient mixing and combustion, widely adjustable rocket, widely applicable variable geometry inlet/nozzle design and control, multi-mode flow passage design, and robust mode transition. Several inherent scientific issues involved in these technologies are refined, such as the dynamic air ejection mechanism, combustion and thermal choke mechanism, and the coupling mechanism between air ejection and thermal choke. Finally, the historical development trend of ejector mode research is clarified, and some recommendations for performance improvement and the key technology breakthrough are provided for future ejector mode research of RBCC engines.

中文翻译：

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火箭基联合循环发动机喷射器模式研究进展

摘要 火箭基联合循环（RBCC）发动机被认为是可重复使用的空间运输车辆和高超音速巡航车辆最有效的推进系统之一。它通过多模式运行，有效地结合了火箭发动机的高推重比和吸气式发动机的高比冲，可以在非常广泛的马赫数和飞行高度范围内表现出色。作为RBCC发动机最显着的特点和优势之一，弹射模式是支持飞行器快速加速和爬升的重要模式。发动机性能，尤其是喷射器模式下的比冲，在决定总油耗、整个 RBCC 发动机的推进效率、以及整个飞行轨迹。因此，在喷射器模式下的优异性能足以保证RBCC发动机的竞争力和应用前景。本文对不同国家、不同历史时期RBCC发动机喷射方式的研究进展进行了全面系统的回顾。在调查中，总结概括了喷射器模式研究的进展情况，涵盖了不同历史时期喷射器模式研究的大量具有里程碑意义的实验和应用成果。在此基础上，提出了与喷射器模式研究相关的多项关键技术，包括高效喷射、高效混合与燃烧、广泛可调的火箭、广泛适用的可变几何入口/喷嘴设计与控制、多模式流道设计，稳健的模式转换。这些技术涉及的几个内在科学问题得到了提炼，例如动态空气喷射机制、燃烧和热阻流机制、空气喷射和热阻流之间的耦合机制。最后，阐明了喷射模态研究的历史发展趋势，为RBCC发动机喷射模态研究的性能提升和关键技术突破提出了一些建议。