Experimental research on start characteristics of a hypersonic inward-turning inlet

This paper presents a qualitative experimental research on start characteristics and flow control of a typical hypersonic inward-turning inlet. Designed at Ma6.5, the inlet is an ERST(Elliptical-to-Round Shape Transition) one, of which the internal contraction ratio and the total contraction ratio are 1.7 and 5.8, respectively. The throat section of the inlet is a round cross section with a diameter of 50mm. The whole length of the inlet is about 950mm. Using AHL3D CFD software, some numerical simulations are carried out, of which the result shows that the inlet can start but can't self-start at Ma5. Utilizing the same AHL3D, some researches of fluid bleeding on the inlet shoulder are conducted, of which the result shows that the inlet can self-start at Ma5 with a loss mass flow less than 1%. On the base of the numerical simulation, an inlet model with a scale of 1:1 is manufactured and some qualitative experiments are launched in a routine hypersonic blow-down wind tunnel of CARDC. By the means of the silk-thread flow visualization and the real-time throttle and the switch of the bleeding module, the start characteristics of the inlet with/without flow control are got from the experiments. The experiments verify the numerical result that the inlet can't self-start at Ma5 without bleeding. When the bleeding-area ratio is about 0.15, the inlet can self-start. The qualitative experiments also preliminarily verify the design method and the computational method of start characteristics for such inward-turning inlets. At the same time the results of the current experiments can provide a convenient and rapid silk-thread flow visualization method to judge the start states of an inlet in such routine wind tunnel.