输气管道泄漏音波信号传播特性及预测模型

输气管道泄漏音波在管内传播过程中发生衰减,在安装音波传感器前必须明确管内音波信号的传播距离。综合考虑介质黏滞吸收和热传导作用及特殊管件(弯管、分支及变径管)的吸收作用,建立泄漏音波在管内传播模型。利用改进的小波分析法对泄漏音波信号时频域特征进行分析,模拟分析不同特殊管件对音波传播的影响,并利用高压泄漏试验装置对建立的传播模型进行验证。结果表明:泄漏音波在管内以平面波形式传播,泄漏信号幅值能量占优的频带主要集中在0～0.366 Hz及2.93～46.88 Hz内,直管和弯管对音波衰减影响较小,只有分支和变径(变径流量计、阀门)对音波传播影响较大;得到的拟合音波吸收系数与理论吸收系数吻合较好,模型计算结果较为准确,可提高音波泄漏检测的准确性。

Propagating characteristics of acoustic leakage signal in natural gas pipeline and establishment of prediction model

The acoustic signals collected from natural gas pipeline leak detection inevitably attenuate as they propagate in the pipeline, and the propagation distance of acoustic signals must be calculated before installing acoustic sensors. With regard to the viscous absorption, heat conduction of medium and the absorption of the special pipe fittings (elbows, branch and adjustable tube), the propagation model of acoustic signals was established. The characteristics of acoustic leakage signals in time-frequency domain were analyzed by the improved waveform analysis method. The effects of different special fittings on sound wave propagation were simulated, and the acoustic propagation model was verified by a high pressure leakage test device. The results show that the acoustic leakage signals in the gas pipeline propagates in the form of plane wave, and the energy of acoustic leakage signals is concentrated in the 0-0.366 Hz and 2.93-46.88 Hz. The straight pipe and elbows have little effect on the propagation of acoustic signals, while branches and adjustable tube have great impact on the propagation. The acoustic absorption coefficient fitted by experimental data agrees well with that calculated by the propagation model, which proves the accuracy of the propagation model. The accuracy of the acoustic leakage detection is improved.