超声速燃烧的激波作用低温稳定燃烧机理及速率耦合控制原理

Lasted nearly sixty years, the flight test of the X43 based on hydrogen fueled supersonic combustion and the X51 based on hydrocarbon fueled supersonic combustion gain preliminary success. However, a key to restrict their rapid development is that there are lots of basic scientific problems unresolved. The most critical problem is how to obtain enough thrust by the supersonic combustion based on hydrocarbon fuel. The essence of solving this problem lies in the cognition of highly coupled mechanism between the flow process and the combustion of processes within hydrocarbon fuel scramjet, and lies in the knowledge from the principle of stable ignition and combustion stability of hydrocarbon fuel under extreme conditions with high-speed and low temperature. This problem is the research hotspot of engineering and academic circles. Aiming at the common problem existing in both scramjet engineering and supersonic combustion theory, “Supersonic Ignition and Stable Combustion of Hydrocarbon Fuels”, this proposal is focused on the acknowledgement of shock-influenced combustion mechanism and fundamental physical disciplines in low-temperature and other extreme conditions, in accordance to the development of the supersonic combustion fundamentals in high-speed and low-temperature extreme environments. From the aspects of the flow structure and low-temperature combustion, the coupling control method can be summarized to direct the design of hydrocarbon scramjets. Supersonic combustion theory in extreme conditions is also to be developed, which will further promote the development of combustion theory.

历时近六十年，基于氢燃料超声速燃烧的X-43及基于碳氢燃料的X-51试验取得初步成功，然而制约其快速发展的关键在于：大量基础科学问题仍未解决。其中最关键的问题就是碳氢燃料超声速燃烧如何获得足够的正推力。解决此问题的本质在于认知碳氢燃料超燃发动机流动过程与燃烧过程高度耦合的机理，掌握高速低温极端环境下碳氢燃料稳定点火燃烧原理。这个问题是工程界和学术界共同的研究热点。本项目选择碳氢燃料超燃冲压发动机与超声速燃烧理论的共性问题“碳氢燃料超声速点火及燃烧稳定性”为研究对象，以发展碳氢燃料高速低温极端环境下超声速燃烧控制原理为目标，重点完成对激波作用下的稳定燃烧机理以及低温燃烧基本物理规律的认知。从流场结构和低温燃烧角度归纳总结出可指导碳氢超燃冲压发动机设计的速率耦合控制方法，并进一步发展极端条件下的超声速燃烧理论，推动燃烧科学的理论发展。

缺乏对超声速流动与燃烧高度耦合过程的认知是制约碳氢燃料超燃冲压发动机快速发展的关键问题之一。本项目聚焦碳氢燃料超燃冲压发动机与超声速燃烧理论的共性问题，以发展碳氢燃料高速低温极端环境下超声速燃烧控制原理为目标，重点完成对激波作用下的稳定燃烧机理以及低温燃烧基本物理规律的认知。一方面，发现了可压缩涡环的极限生长和夹止特性以及可压缩涡环发生夹止对应的时间尺度具有一定的普适性。研究了涡形态演化与混合过程的内在关系，揭示了激波作用下的涡致极限混合规律。揭示了非定常涡结构演化规律与燃烧效率的内在机制，通过拉格朗日粒子追踪技术，验证了通过改变流动结构提高燃烧效率的合理性。并基于发展的高效微观算法研究了多尺度范围内粘性扩散效应对燃烧过程的影响规律，从分子碰撞和粘性扩散角度揭示了激波宽度尺度范围下的流动燃烧耦合机制。相关机理和理论研究成果发表在JFM、CNF、JCP和POF等国际顶尖期刊上。本项目对超声速流动与燃烧耦合过程的深入认知推动了极端环境条件下超声速燃烧科学理论的发展。另一方面，基于液态碳氢燃料的燃烧特点，建立了扩散燃烧的非定常着火准则，发现活化能和蒸发速率对自燃温度的影响存在最优比例关系，为低温环境下的自燃燃料设计提供了重要的理论指导。通过碳氢燃料分子设计制备点火燃料，实现了超燃总温800K条件下的自点火技术。试验验证结果表明该技术不仅点火可靠性高，而且具有10-15%的推力增益。碳氢燃料超燃环境下超低温自燃点火技术使我国在超燃冲压发动机低马赫数启动问题上达到国际先进水平。