Investigation Of The Unstart State Of Inward Turning Hypersonic Inlet

Inward turning inlet is a special hypersonic inlet type which caused extensive concentrationrecently. The unstart state of inward turning hypersonic inlet was investigated in this thesis. Firstly,the flow-structure of the unstart state which caused by downstream choking was investigated usingCFD and experiment method. Results show that the inward turning inlet is buzzing in unstartscondition. Period movement of the bump and the shock can be seen in the buzzing, and the pressurealong the inlet is floating too. The critical throttling ratio which raised the inlet to be unstarting wasreceived. And it was between25%and36%. The influence of the throttling ratio on the unstartingcharacter of inward turning inlet was investigated. It was found that the buzzing period of the inlet isrising as long as the throttling ratio rose. Secondly, another kind of unstart state of the inward turninginlet which caused by working at low Mach number was investigated. CFD results showed that it isdifferent from the unstart phenomena caused by downstream choking, the bump and the shock werestable without buzzing. Furthermore, the influences on the start characteristics of differentconfiguration parameters of the inward turning inlet were researched. It shows that the starting abilityof the inward turning inlet was enhanced as long as the aspect ratio of the entry shape rose. At last,making bleeding slot on both up-wall and side-wall was proposed to increase the starting ability of theinward turning inlet. And the influences of the position and width of the slot were investigated.Results showed that: It will be better if the slot is set at the end of the bump and2.5mm is accepted asthe width of the slot. Using this, the restart Mach number of the inward turning inlet was decreasedfrom4.4to3.2.