Numerical Analysis Of Non-Classical Isolators' Flow Characteristics And Aerodynamic Performance

Isolator plays a key role in hypersonic propulsion system and its performance critically influences the system's stably working region. Based on the three-dimensional CFD calculation results, the flow characteristic and aerodynamic performance of the non-classical isolators including Ellipse Isolator,Rectangular-to-Ellipse Isolator and Rectangular Isolator, are detailed studied in this paper.Firstly, it is showed that the shock train structure and the flow characteristic are decided by the cross-section shape, which consequently leads to different performance of isolators. When the upstream Mach number is above 2.0, the shock train structure and the flow characteristic becomes unsymmetrical even the incoming flow condition is symmetrical. The influence of different cross-section shapes on the aerodynamic performance of the isolators is discussed secondly.. The ellipse isolator's ability to support back pressure is the best, and the rectangular one is the poorest, while the rectangular-to-ellipse one becomes the medium one. As the ratio of major axis to minor axis decreases , the Ellipse Isolator's ability to support back pressure is becoming better, which made it clear that the circular isolator will be the best one. As to the Rectangular-to-Ellipse Isolator, its ability to support back pressure is infected by the law of cross-section shape transition. The Rectangular Isolator can only support low back-pressure when the ratio of width to height is high. Although the Mach number and temperature of the isolator outlet are independent of the cross-section shape, it is found that the total pressure recovery is quite sensitive to the the shape. And the numerical results showed that the total pressure recovery of the Ellipse Isolator is the largest and the Rectangular-to-Ellipse one is the lowest.Finally, the effect of incoming flow to isolator's performance is studied. When the upstream Mach number grows up, the back pressure could be supported for the isolatrs will be enlarged. At the same time, the total pressure recovery and mach number of outlet will come down while the temperature keeps rising. Especially, for the Ellipse Isolator, whatever the upstream Mach number is, the mach number of outlet keeps unchanged once back pressure reaches maximum.It is believed that the conclusions in this paper might be useful for the following hypersonic isolator design work.