Abstract: In order to adapt with the modularity design of the scramjet and the requirement of the circle combustor，the shape of the isolator must be designed from rectangular to circular. Based on the method of super-elliptic curves for cross-section transition ，a rectangular-to-circular isolator was designed，which was investigated with numerical simulation and experiment in a supersonic wind tunnel under an incoming asymmetric flow of Mach number 2.1. The results indicate that under the same back pressure，the total pressure recovery coefficient of rectangular-to-circular isolator are improved by 4% and 5% than the rectangular isolator at two kinds of incoming flow. Under incoming asymmetric flow，trends of the wall pressure in the two kinds of isolator are the same: the forepart of the top wall pressure of the isolator fluctuates up，the latter part of top wall pressure and bottom wall pressure both arises slowly up. The total pressure recovery coefficient decreases when the back pressure rises. The rectangular-to-circular isolator can withstand a maximum back pressure of 4.1 times static pressure. The total pressure recovery coefficient of outlet is 0.505 under the maximum back pressure.

Key words: Scramjet；Isolator；Rectangle-to-circle；Shock train；Wind tunnel test

摘要： 为了适应超燃冲压发动机模块化设计及圆形燃烧室的需求，隔离段必须设计成矩形截面渐变为圆形出口的形状。发展了一种基于超椭圆曲线的截面渐变方法，以此设计了矩形转圆隔离段，开展了数值模拟研究并进行了在Ma=2.1且来流条件非对称下的矩形转圆隔离段吹风实验。研究结果表明:在反压相同时，两种不同来流条件下矩形转圆隔离段的出口总压恢复系数较等直矩形隔离段分别提高了4%和5%；在非对称来流实验条件下，矩形转圆隔离段壁面沿程压力分布规律与等直矩形隔离段压力分布规律趋势一致，上壁面沿程压力曲线前部呈波动式上升，后半部上升平缓，而下壁面沿程压力曲线整体上升较为平缓，随着出口反压的增大，总压恢复系数随之减小，矩形转圆隔离段最大能够承受4.1倍的来流静压，极限反压状态下出口总压恢复系数为0.505。

关键词: 超燃冲压发动机；隔离段；矩形转圆；激波串；风洞实验