关键词: 高速气流, C/SiC薄板, 热声耦合, 动响应, 热声激励试验

Abstract:

The thermo-acoustic problem of thin-walled composite structures under high-velocity gas flow is one of the core issues that have long been of concern in the aerospace field. In this paper， a combination of numerical simulation calculation and thermo-acoustic excitation tests is adopted to conduct thermo-acoustic excitation tests on thin plates for obtaining the natural frequency， acceleration frequency domain response and unidirectional strain results of the thin plates. The control equation for large deflection of thin plate structures is established. By applying the coupled Finite Element Method/Boundary Element Method （FEM/BEM） theory and combining the sound field vibration coefficient matrix with the structural control equation， the frequency response function of the structural sound pressure can be obtained， thereby reflecting the coupling effect. The natural frequency and unidirectional strain values of the thin plate structure are calculated under the same test conditions. By comparing them with the test results， we verify the validity of the thermo-acoustic coupling calculation method and model， and then complete the calculation and law analysis of the thermo-acoustic coupling response characteristics of the CMCs（Ceramic Matrix Composites） thin plate structure under high-velocity gas flow. The analysis of the results shows that under the multi-field coupling of heat， flow and sound， the flow velocity controls the total pressure， and the maximum pressure is concentrated at the inlet. The temperature collaborates with the thermal baseline and flow gradient to regulate the temperature distribution of thin plates. Temperature dominates the stress distribution and amplitude， and changes the location of dangerous points. The stress and strain responses first decrease and then increase with the flow rate， and the extreme values are concentrated in the high-temperature and high-flow rate zone， reflecting the orthogonality of the structure. Thermo-acoustic loads and flow loads separately control low- and high-frequency responses. Temperature drives the peak migration of stress Power Spectral Density （PSD）. At high temperatures and high flow rates， thermal and flow loads become dominant in the frequency domain.

Key words: high-velocity airflow, C/SiC thin plate, thermo-acoustic coupling, dynamic response, thermo-acoustic excitation test