Abstract: The performance of Rectangular-to-Circular isolator based on super elliptical method affected by various factors such as back pressure，incoming Mach number and boundary layer thickness was investigated with numerical simulation under asymmetric incoming flow. The results show that the interaction of back pressure and boundary layer leads to the initial shock wave form gradually transforming into "λ" shock，and the increase of back pressure results in the decrease of isolator’s performance，the sharp increase of low energy flow region，as well as the decrease of the asymmetric effect of flow field. Meanwhile the increase of incoming Mach number leads to the improvement of the withstand back pressure capability of isolator，while the effect of asymmetric flow field declined consequently，especially the total pressure recovery coefficient of outlet section decrease 7.2% while incoming Mach number of 2.5 compared with situation where Mach number is 2. The increase of boundary layer thickness contributes to deterioration of the flow separation in the isolator，which further results in the decline of the withstand back pressure capability of isolator，which is not conducive to the quality of the exit flow field of isolator. When the dimensionless thickness of boundary layer is 0.33，the total pressure recovery coefficient of outlet section under asymmetric incoming flow declines 13.7% than it is under uniform inflow.

Key words: Scramjet；Isolator；Rectangular-to-circular；Asymmetric incoming flow；Numerical investigation

摘要： 针对采用超椭圆曲线方法设计的矩形转圆隔离段，在非对称来流条件下，利用数值模拟手段研究了出口反压、来流马赫数、进口附面层厚度等因素对其性能的影响。研究结果表明:出口反压与附面层相互作用导致初始激波形态转变为“λ”激波，并且隔离段的性能随着反压的增大而下降，低能流区域迅速增长，流场非对称效应逐渐变小；来流马赫数的增大会提高隔离段的抗反压能力，并且会降低流场的非对称效应，但出口总压恢复系数却随之下降，特别是与来流马赫数为2情况相比，当来流马赫数为2.5时其降低了7.2%；进口附面层厚度的增加会加剧隔离段内的流动分离，导致隔离段的抗反压能力降低，不利于隔离段出口流场品质，并且相对于均匀来流而言，当进口附面层无量纲厚度为0.33时出口总压恢复系数下降了13.7%。

关键词: 超燃冲压发动机；隔离段；矩形转圆；非对称来流；数值模拟