Real-time unstart prediction and detection of hypersonic inlet based on recursive Fourier transform

Unstart is an abnormal state, and special care is devoted to the phenomenon for a hypersonic inlet. In this article, the process of a two-dimensional hypersonic inlet from start to unstart is experimentally demonstrated by recording the corresponding time history of the wall static pressure. The precursor signal analysis is conducted to accomplish the inlet unstart prediction and detection first, and the results indicate that the fluctuation of shock train at T14 can be the precursor of inlet unstart. Then the algorithm description of recursive Fourier transform is given and introduced to solve the inlet unstart prediction and detection. The detailed application, influence of some specific parameters and verification are also discussed. According to the experimental data, the alarm time calculated by recursive Fourier transform is approximate 602 ms and 166 ms for Run 1 and Run 2 respectively, which verifies the feasibility of the methods adopted.