轴流风扇/压气机管道周向声模态的测量

利用管道内部周向均匀分布的麦克风阵列对某单级风扇在高背景噪声和较大硬壁反射条件下的管道周向声模态进行了实验测量.利用与参考信号互相关(CC)模态分解技术和传统的方均根(RMS)模态分解技术得到了主要的周向声模态振幅.通过与Tyler和Sofrin的理论分析对比,发现在高背景噪声和较大硬壁反射条件下,两种模态分解技术都能获得较为理想的模态分解结果;并且发现CC模态分解技术获得的模态振幅较低,初步分析这是由于和RMS模态分解技术相比,CC模态分解技术可以降低随机噪声对模态振幅分解结果的影响.此外,周向麦克风个数大于所要分解周向声模态阶数的4倍时,使用CC模态分解技术获得的模态振幅误差可以控制在1dB之内. 

In-duct circumferential acoustic mode measurement of axial fan/compressor

In-duct circumferential acoustic mode of a single stage fan was measured using equidistant microphone array with high back ground noise and high rigid wall reflection. Primary circumferential acoustic mode amplitude was obtained by utilizing the cross-correlated(CC) reference channel mode detection technique and the conventional root mean square-averaging (RMS) mode detection technique. The results were compared with Tyler and Sofrin's duct mode theory, finding that both CC mode detection technique and RMS mode detection technique can obtain the ideal mode detection results with high back ground noise and high rigid wall reflection, and the mode amplitude of the former was lower than that of the latter. This is because CC mode detection technique decreases the impact of random noise on the mode amplitude. It is also found that the error of mode amplitude from CC mode detection technique is lower than 1dB when the number of microphone in the circular microphone array is more than four times of the circumferential acoustic mode order.