液态燃料在高速气流中的雾化、蒸发和燃烧

The fragmentation, vaporization and combustion of liquid fuels in high-speed flows pose the key technological threshold in the development of new generation engines for hypersonic vehicles domestically and internationally. Although many years of efforts have been made in the academia and industries, no significant breakthrough has been done. In order to enhance the applicability of the existing theories, in this project, combined endeavors of theoretical derivation, numerical simulation and experimental verification will be launched to build a modern theory of the fragmentation, vaporization and combustion of liquid fuels in high-speed flows. In the theoretical derivation aspect, Rayleigh-Taylor and Kelvin-Helmholtz linear instability analyses on the fuel droplets in the compressible gas flow will be conducted to elucidate the effects of fuel properties (such as density, viscosity and surface tension), initial droplet dimensions, free-stream temperature, and Mach number on the critical wavelength. The derived theory will form the cornerstone of the new theory of the fragmentation, vaporization and combustion to be built; meanwhile, contemporary domestic and international experimental results will be searched and put together, with the input of the derived theoretical results, to correlate a simplified and applicable model for the following numerical simulations and future engineering applications. In the numerical simulation aspect, the novel CE/SE algorithm will be developed as the platform for exploring the characteristics of fragmentation, vaporization and combustion of liquid fuels in high-speed flows and for supporting the theory development. In the experimental efforts, a detonation tube using flashing boiling atomized liquid fuels will be designed and built to validate the model and numerical method developed. The outcome of the project will contribute to the existing knowledge on the fragmentation, vaporization and combustion of liquid fuels in high-speed flows and lay down a solid scientific foundation for its future exploration. The project is deemed to have significant scientific value and great potential for future engineering applications.

液态燃料在高速燃烧过程中的雾化、蒸发和燃烧是目前国内外新型发动机中企待解决的关键性问题，虽经过多年的努力，但是至今没有取得突破性进展。本项目期望克服可压缩气流中液滴破碎相关理论模型的不足，以理论、数值方法与实验验证构建燃料液滴在可压缩气流中破碎机理的新理论。理论方面，拟针对液滴在可压缩流中的线性不稳定性进行分析，阐明不同液滴物性（密度、粘性、表面张力）及初始尺寸、气流温度与马赫数对最不稳定波长的影响，为建立破碎模型提供理论依据。同时参考最新的国内外液滴破碎的实验结果，提出一简化的实用模型；数值方面拟建立最新时空守恒元/解元（CE/SE）数值模拟平台，开展液滴在可压缩气流中的破碎、蒸发和燃烧特性研究；实验方面则将建立一闪沸雾化的液态燃料爆轰管，进行理论与数值方法检验。预期成果有望提升现有液态燃料在高速燃烧问题的理论水平，并为发展有效的应用技术提供科学依据，因此，具有重要的科学价值和应用前景。

该项目旨在提升当前对于液态燃料高速燃烧问题的认知水平，为液态燃料在高速燃烧过程中的雾化、蒸发和燃烧现象提供有效的应用技术和科学依据，具有重要的科学价值和应用前景。项目组针对所研究课题进行了实验、数值以及理论方面的深入研究，从基础问题入手，对物理现象内在机理进行了深入剖析。..实验方面，项目组自行设计并建成了一套激波管和光学成像系统，用于开展激波冲击下的液滴破碎过程研究。利用该实验设备开展了一系列高韦伯数液滴破碎模式实验，获得了清晰的液滴破碎过程，获得了对激波冲击导致的液滴变形和破碎的深入了解，并为数值模拟提供了可靠的参考依据。.数值方面，项目组成功构造了迎风型时空守恒元/解元（CE/SE）格式，并将其用于求解简化的五方程模型，成功实现了对两相流问题的数值模拟；在爆轰波的研究中采用了最新的氢氧反应模型，建立了可靠精确的可压缩化学反应数值模拟平台，对分子振动非平衡效应进行了探讨，提出了分子振动非平衡效应对爆轰波胞格尺寸的影响。发展了Eulerian-Lagrangian方法对多分散悬浮颗粒气相介质中的爆轰波进行了研究，揭示了在爆轰波研究中考虑颗粒尺寸的重要性。.理论方面，基于液滴破碎的实验和数值模拟结果，对液滴破碎现象的初期变形过程进行探讨，建立了激波对液滴内部流场变化的相关关系，进一步完善对于液滴破碎过程的认知；基于振动非平衡效应的研究，对ZND爆轰模型进行了改进，获得了更为精确可靠的理论模型。