压气机旋转不稳定性的周向模态特性及其分解方法

基于实验和数值模拟的方法,研究压气机叶顶区域不稳定压力波的周向模态特性。使用基于空间傅里叶变换的周向模态分解方法对实验和数值计算结果进行了分析,给出了实验和数值计算结果的频谱模态分解结果,得到了压气机连续周向模态特征频谱峰值。对压气机叶顶区域各模态幅值和相位的时变特性做了详细分析,得到了叶顶旋转不稳定性周向模态传播速度和传播方向。结果表明:旋转不稳定性的主模态具有稳定的周向传播结构,而其他模态波的幅值和相位存在较大波动。利用多组有限测点组合方式消除了模态混叠现象影响,将可以分析的模态上限提高数倍,取决于测点数的选择；基于该方法可以用有限测点捕捉高阶模态,大大减少了实验所需的传感器数目。 

Circumferential mode characteristic of rotating instability and its decomposition method of compressor

Unsteady pressure fluctuations near tip region in an axial compressor were studied using experimental and numerical methods. A circumferential mode decomposition method based on spatial Fourier transform was used to deal with the circumferential pressure data. Spectrum analysis of experimental and numerical results was performed, proving the existence of circumferential modes which can be continuously numbered. The temporal evolution of these circumferential modes were resolved, showing a stable circumferential propagating structure near tip region of the dominate mode of rotating instability, and the other mode components presented a more fluctuating characteristic. Besides, a prediction method for circumferential modes of higher orders was given using two sets of measuring points to deal with the aliasing effect. The method improved the upper bound of the mode number that can be analyzed for several times, and much fewer sensors would be required when applying it to experimental measurements.