The ejector mode of the Rocket-Based Combined-Cycle (RBCC) engine is characterized by high fuel consumption. This study is aimed at investigating the influence of the rocket fuel-rich degree on the RBCC engine’s performance under the ejector mode combined with simultaneous mixing and combustion (SMC). Numerical simulations were conducted for various rocket mixing ratios () under subsonic () and supersonic () flight conditions. It was observed that a high fuel-rich degree in the rocket plume negatively impacts the eject performance under all conditions. However, it improves the overall performance () at high flight Mach numbers (). For supersonic conditions, increasing the fuel-rich degree promotes greater fuel participation in combustion, thereby enhancing RBCC engine performance. Nevertheless, the subsonic-supersonic mixing layer exhibits low evolution, resulting in a decrease in reaction efficiency from 29.2% to 12.0% as the decreases from 3.2 to 1.6. Consequently, there is an inefficient utilization of fuel. To optimize RBCC engine performance, the rocket fuel-rich degree can be appropriately increased. However, this increase should be limited to prevent fuel wastage arising from low reaction efficiency. Under subsonic conditions (), the low kinetic energy of captured air leads to the occurrence of “negative thrust surface” and “wall impact” phenomena, which hinder the efficient and stable operation of the RBCC engine. Consequently, adjusting the fuel-rich degree alone cannot promote specific impulse (), and a low fuel-rich degree is considered an ideal strategy when combined with adjustable nozzle technology.

中文翻译：

---

喷射模式下RBCC发动机富油程度影响的数值研究

火箭联合循环（RBCC）发动机喷射模式的特点是油耗高。本研究旨在研究喷射器同时混合燃烧（SMC）模式下火箭燃料富集程度对RBCC发动机性能的影响。对各种火箭混合比进行了数值模拟（）在亚音速（）和超音速（)飞行条件。据观察，火箭羽流中的高燃料丰富度会对所有条件下的弹射性能产生负面影响。高飞行马赫数 ( ) 下的整体性能 ( ) 。对于超音速工况，提高燃料富集度可以促进燃料更多地参与燃烧，从而提高RBCC发动机的性能。然而，亚音速-超音速混合层表现出低演化，导致反应效率从3.2下降到1.6，从29.2%下降到12.0%。因此，燃料的利用效率低下。为了优化RBCC发动机性能，可适当提高火箭燃料富集度。然而，这种增加应该受到限制，以防止由于反应效率低而造成燃料浪费。在亚音速条件下（），捕获空气动能低，导致“负推力面”和“撞壁”现象的发生，阻碍了RBCC发动机的高效稳定运行。因此，单独调节燃料富集度并不能提高比冲量（），当与可调喷嘴技术相结合时，低燃料富集度被认为是一种理想的策略。