Investigation For The Rectangular-to-Circular Isolator Under Asymmetric Supersonic Flow

In order to adapt with the modularity design of the scramjet and the requirement of the cir-cle combustor, the shape of the isolator must be designed from rectangular to circular.Currentresearch on the isolator was under the symmetric coming flow. But the incoming flow at inlet ofisolator is very complex, mostly under the asymmetric coming flow. The author makes a studyby using numerical simulation and wind tunnel test to analyze the problems.Based on the method of super-elliptic curves for cross-section transition, a rectangular-tocircular isolator was designed. The flow characteristics in the rectangular-to-circular isolatorwere investigated with numerical simulation under an asymmetric incoming flow. In addition,comparisons of the performance were carried out under different incoming flow and two kinds ofisolator. The result showed that: The performance of isolator decrease when the back pressureincrease; the total pressure recovery coefficient of rectangular-to-circular isolator improve5%than the rectangular isolator’s; the asymmetric incoming flow would reduce the shock holdingcapability; the maximum back pressure is improved when Mach number increase; the increasingthickness of boundary layer would lead the total pressure recovery coefficient and the shockholding capability both decreasing.Investigation for the isolator was carried out under the complicate environment with nu-merical simulation. The result indicated that: The surface roughness would reduce theback-pressure capability; the shock holding capability decrease when the total temperature rises.Experimental was conducted in a blow-down supersonic wind tunnel under an asymmetricincoming flow of Mach number2.1.The results indicated that: trends of the wall pressure in thetwo kinds of isolator is 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 rise slowly up. The initial posi-tion of the shock train moves forward and total pressure recovery coefficient decrease when theback pressure rises. The rectangular-to-circular isolator could withstand with4.1times the staticpressure. The total pressure recovery coefficient is0.505under the maximum back pressure. Thepressure recovery coefficient decrease4%and the maximum back pressure decrease8%com-pared with symmetric incoming flow.