Abstract The performance of a scramjet engine relies heavily on the combustion characteristics of fuel. This work aims to propose a concept of controlling the self-starting characteristics and propulsion performance of a scramjet via fuel reactivity modification. The fuel reactivity was modified by adjusting the activation energy of each elementary reaction. The thermodynamic analysis was then systemically performed to evaluate the effects of fuel reactivity on the lowest flight Mach number required for self-starting and the specific thrust. The results indicate that the lowest flight Mach number for self-starting of a hydrogen-fueled scramjet reduces from 6.2 to 5.1 when the activation energy is decreased by 50%. Under a given flight condition, fuel reactivity has a remarkable influence on the characteristic ignition length, which affects the specific thrust, especially at low flight Mach numbers. It is demonstrated that there exists an optimal reaction rate to achieve the maximum specific thrust, rather than increase the reaction rate infinitely. The optimal reaction rate relates to the supersonic flow condition, the exothermic heat of fuel, and the wall friction. The results obtained in this investigation provide a theoretical basis for the design of high-reactivity supersonic combustion fuel and further research of advanced scramjet engine operation.

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燃料反应性控制的超燃冲压发动机自启动和推进性能：模型研究

摘要 超燃冲压发动机的性能很大程度上取决于燃料的燃烧特性。这项工作旨在提出一种通过燃料反应性改性来控制超燃冲压发动机的自启动特性和推进性能的概念。通过调整每个基本反应的活化能来改变燃料反应性。然后系统地进行热力学分析以评估燃料反应性对自启动所需的最低飞行马赫数和特定推力的影响。结果表明，当活化能降低50%时，氢燃料超燃冲压发动机自启动的最低飞行马赫数从6.2降低到5.1。在给定的飞行条件下，燃料反应性对特征点火长度有显着影响，这会影响比推力，尤其是在低飞行马赫数下。结果表明，存在一个最佳反应速率来实现最大比推力，而不是无限增加反应速率。最佳反应速率与超音速流动条件、燃料放热和壁面摩擦有关。研究结果为高反应性超音速燃烧燃料的设计和先进超燃冲压发动机运行的进一步研究提供了理论依据。和壁面摩擦。研究结果为高反应性超音速燃烧燃料的设计和先进超燃冲压发动机运行的进一步研究提供了理论依据。和壁面摩擦。研究结果为高反应性超音速燃烧燃料的设计和先进超燃冲压发动机运行的进一步研究提供了理论依据。