高超声速1 MHz 高频脉动压力测试技术及其应用

为了研究高超声速边界层内的高频脉动结构，特别是第二模态不稳定波，在 FD-07风洞中搭建了一套1MHz 量级高频脉动压力采集系统。风洞背景噪声和电磁噪声是影响高频脉动结构测量的主要原因。在风洞流场品质无法改变的前提下，对高频脉动压力采集系统的信号传输进行了改进，包括工频电源隔离、传输电缆屏蔽和采集设备接地等。通过改进措施，采集系统的抗电磁干扰和信号衰减的能力得到改善，其信噪比得以显著提升。结果表明，改进前后各频段噪声的能谱密度大幅降低(在频率400 kHz 以下，噪声能谱密度降低了一个量级以上)。最后，利用该测试技术成功地在 FD-07高超声速风洞中进行了边界层稳定性实验，捕捉到了第二模态不稳定波，其主导频率范围与线性稳定性理论预测结果吻合。

Hypersonic high frequency (1 MHz)fluctuation pressure testing technology and application

High frequency (1 MHz)fluctuation pressure acquisition system was developed to study the high frequency fluctuation structures,especially the second mode instability waves,in hypersonic boundary layer in the FD-07 wind tunnel. Wind tunnel ground noises and electromagnetic noises affects measuring of high frequency fluctuation structures.Due to When the qualities of wind tunnel flow field can’t change,a series of improvements were made for signal transmission of the system to enhance the ability of anti-electromagnetic interference and anti-attenuation.The improvements contained power supply isolation,shielding cable and ground connection,et al.The experimental results by comparison showed that signal to noise ratio (SNR)of the acquisition system increased remarkably,and the power spectrum densities of noises below 400 kHz were reduced by one order of magnitude.Finally,hypersonic boundary stability experiment was performed successfully with the acquisition system in FD-07 tunnel.The second mode wave was detected,and the main frequency extent agreed with the results of linear stability theory (LST).