Research on the Identification Method of Flow Modes during the Hypersonic Inlet Unstart/Restart Process

In air-breathing hypersonic flight, when the flow conditions upstream and downstream are not appropriate, the air inlet is prone to failure to start, which can lead to engine stall or even flight failure. Therefore, real-time identification methods for air inlet flow modes must be developed. This paper takes the hypersonic inlet as the research object. In the wind tunnel experiment, the switching of the inlet unstarting/restarting was achieved by changing the Angle of attack, and the shadow images during the mode switching process and the pressure signals of multiple wall measurement points were obtained. The study shows that the traditional modal recognition method based on pressure amplitude, standard deviation, and power spectrum has a weak ability to recognize the starting/unstarting flow modes of the inlet in this paper. For this purpose, this paper proposes a flow mode recognition method based on pressure difference and standard deviation, which can achieve good recognition ability for each measurement point and has strong applicability. In addition, the method identifies the unstart point and the restart point separately instead of using a single detection threshold for judgment, significantly improving the accuracy of flow mode identification.