压气机叶顶区域周向模态特性的实验

Experiment on circumferential mode characteristics of axial compressor tip flow

针对压气机叶顶区域流动周向模态测试对传感器数量的要求及传感器数量受限时所产生的模态混叠现象,提出一种基于两套测点数组合来校准预测高阶周向模态的方法。结果表明:应用该方法,在实验测试中将可识别的模态阶数提升至原来的5倍。研究了轴流压气机叶顶区域压力脉动,捕捉到包括叶片通过频率(BPF)和旋转不稳定性频率(RIF)带凸起的叶顶区域流动模态特性。随着流量减少,频谱上对应的宽频带凸起结构向低频移动,主要周向模态阶数降低,但旋转角速度有所上升。压气机叶顶区域流动的时变特性分析表明,旋转不稳定性在时域上幅值波动较大,不稳定性明显。

Experiments measuring circumferential mode characteristics of compressors were made for the high demand for the number of sensors,and the aliasing of circumferential wave number when insufficient sensors were provided.A calibration and prediction of higher circumferential mode numbers was proposed using two sets of measuring points,unsteady pressure fluctuations near the tip region in an axial compressor were studied experimentally using this method and the upper limit of identifiable mode numbers was five times of the original method.Circumferential mode characteristics were captured both on blade passing frequency（BPF）and rotational instability frequency（RIF）under several flow conditions.The characteristic spectrum of rotating instability with broadband hump existed within a large range of flow conditions.Both frequency range and dominant circumferential wave number decreased with the flow rate,while at the same time circumferential angular velocity of rotating instability increased;strength of the pressure fluctuations varied significantly in time domain.