Scramjet engines are a suitable replacement for rockets in access-to-space systems, but, being air-breathing engines, their operational envelope is limited to altitudes where enough oxygen is available for combustion. Oxygen enrichment, in which fuel is premixed with oxygen, is a promising technique to overcome constraints in altitude due to low oxygen availability, and the difficulty to generate positive thrust at high Mach numbers. Large-eddy simulations of an inlet-fueled Mach 10 scramjet engine are performed to investigate the effect of oxygen enrichment on the flowfield and to characterize the turbulent combustion regimes. It is shown that combustion levels increase substantially with the addition of premixed oxygen, which leads to a considerable increase in combustion efficiency. It is shown that the mixing process is altered by oxygen enrichment in such a way that the observed increase in mixing efficiency is higher than the increase caused by premixing alone. Finally, the combustion regimes in the simulated engine are analyzed. This shows that combustion is mostly nonpremixed, and oxygen enrichment leads to an increase in premixed combustion, but without significantly altering turbulent combustion overall, which is distributed over a large range of regimes.

超燃冲压发动机是进入太空系统中火箭的合适替代品，但作为吸气式发动机，其运行范围仅限于有足够氧气可用于燃烧的高度。燃料与氧气预混合的富氧技术是一种很有前途的技术，可以克服由于氧气供应量低而导致的高度限制，以及在高马赫数下难以产生正推力。对进口燃料的 10 马赫超燃冲压发动机进行大涡模拟，以研究富氧对流场的影响并表征湍流燃烧状态。结果表明，随着预混氧的加入，燃烧水平显着增加，这导致燃烧效率的显着提高。结果表明，混合过程因富氧而改变，观察到的混合效率增加高于单独预混合引起的增加。最后，分析了模拟发动机中的燃烧状态。这表明燃烧主要是非预混的，富氧导致预混燃烧的增加，但没有显着改变整体湍流燃烧，湍流燃烧分布在大范围的范围内。