Abstract: In order to improve its performance in a wide Mach number range， the variable inlet concept was proposed based on the central-strut rocket-based combined cycle engine (RBCC). Numerical simulations were employed to analyze the flowfield characteristic of the variable inlet concept with the throat height adjustments. Further investigation on the performance comparisons between the variable inlet concept with the throat height adjustments and the variable inlet concept with the throat height - lip position adjustments were carried out. The influence of the lip position imposed on the variable inlet concept was analyzed in detail. The results show that the variable inlet concept with the throat adjustments provides the desired performance parameters in ramjet mode and scramjet mode and achieves the self-started before [Ma∞]=2.4. However， the variable inlet concept with the throat-lip adjustments further decreases the inlet started Mach number and the inlet realizes started before [Ma∞]=1.6. What's more， the variable inlet concept with the throat-lip adjustments also decreases the total pressure loss and increases the mass captured coefficient at partial off-design point. The mass captured coefficient of the variable inlet concept with the throat-lip adjustments increases by 15.1%，40.3% and 15.9% at[Ma∞]=3， 4 and 5， respectively， when compared with the variable inlet concept with the throat adjustments.

Key words: Rocket-based combined cycle；Variable geometry；Inlet；Numerical simulation；Flowfield

摘要： 为提高发动机在宽马赫域下的工作性能，针对中心支板式火箭基组合循环发动机(Rocket Based Combined Cycle，RBCC)，开展了变几何进气道方案设计，通过数值模拟研究了喉道高度调节方案中进气道的流场特征，进一步分析了喉道高度调节方案和唇口位置-喉道高度协同调节方案在性能上的区别，并分析了唇口位置调节对变几何进气道起动性的影响。研究结果表明:喉道调节方案在兼顾亚燃、超燃模态性能需要的同时，能保证进气道在[Ma∞]=2.4前顺利起动；而喉道-唇口调节方案能进一步降低进气道起动马赫数，使进气道在[Ma∞]=1.6前起动，同时能减少进气道的总压损失，并能提高进气道在部分非设计点下的流量系数。相比于喉道调节方案，喉道-唇口调节方案在[Ma∞]=3，4，5下的流量系数分别提高了15.1%，40.3%和15.9%。

关键词: 火箭基组合循环发动机；变几何；进气道；数值模拟；流场