气体管道泄漏模态声发射时频定位方法

针对声发射信号频散特性导致基于时延估计的气体管道泄漏定位误差大的问题,提出一种基于模态声发射时频分析的泄漏定位方法。该方法采用平滑伪Wigner-Ville时频分布对两泄漏信号的互相关函数进行时频分析,利用互相关函数的时频谱可同时提取泄漏信号的时间延迟和与之对应的频率;然后根据泄漏声发射信号的主导模态的频散曲线即可确定该频率对应的声速,利用实时确定的声速和时间延迟并根据两传感器之间的距离即可确定泄漏点的位置。实验结果表明,采用时频分析的气体管道泄漏定位误差与互相关相比减少了6倍。所提出的模态声发射时频定位方法能有效抑制泄漏信号的频散,提高泄漏信号的相关性,从而更适合用于声发射管道泄漏定位。

Leak location in gas pipelines with time frequency analysis of modal acoustic emission using smooth pseudo Wigner Ville distribution

Considering the time delay based leak location errors are large due to the dispersions of gas leak induced acoustic emission, leak location based on modal acoustic emission time frequency analysis is presented. In the scheme, the correlation function is analyzed with the smooth pseudo Wigner Ville distribution. The peak frequency and peak time are extracted simultaneously from the time frequency distribution and the peak time is the time delay between the AE signals collected on either sides of a leakage. The acoustic speed can be determined by substituting of the peak frequency into the dispersive curve of dominant mode in leakage induced AE signal. The leakage can be located with the time delay, the frequency dependant acoustic speed of real time determination and the distance between two acceleration sensors. The proposed scheme is experimentally validated in leak location of gas pipelines and the experimental results demonstrate that the average relative leak location errors are reduced by six times compared with the commonly used correlation based leak location method. The research results also indicate that the time frequency based leak location method can suppress the dispersions of leakage induced AE signal and strengthen the correlation of the leakage induced AE signals. Therefore, the proposed time frequency based leak location method is more feasible for improving leak location in fluid filled pipelines with the AE technique.