Research On Acoustic Monitor System For The Pipeline Leakage Based On Empirical Mode Decomposition

As one of the most widely used energy,oil plays an important part in national economy in our country.The pipeline transportation is regarded as the main mean of oil and gas transportation.With the rapid development of national economy,the distance of pipeline is getting longer and longer.The leakage of pipelines will cause serious consequences,like the ecological environment pollution and the loss of people’s lives and property.The corrosion and leakage of pipelines usually caused environmental factors,but most pipeline leakage accidents in our country are due to criminal drilled holes or carelessly excavation of construction units.At this stage,the common drawback of the domestic pipeline inspection technique is that the leakage can only be positioned after an accident happened.Therefore,how to combine pipeline leakage position and leakage warning and design a set of pipeline leakage monitoring system which can locate the leakage accurately become the key problems of pipeline maintenance.To solve these problems,Empirical Mode Decomposition(EMD)method is applied to the monitoring of typical acoustic signals such as percussions,drillings and leakages of pipelines.The EMD method is used to analyze the typical signals,which is helpful to extract the essential characteristics of the original typical signals and improve the position accuracy.Firstly,the present situation of fluid pipeline leakage detection and main methods used in detecting pipeline leakage currently are summarized.The development and application of the sound wave detection method in the pipeline leakage are emphatically studied.Based on the acoustic of pipeline leakage,the propagation mechanism of acoustic wave in pipelines is analyzed.The wave motion equation of acoustic wave in pipelines is established,and the frequency response of pipeline leakage acoustic wave in pipeline is analyzed.Secondly,in order to solve the filtering problem of acoustic signal,a filtering method that uses empirical mode decomposition(EMD)combined with soft threshold is proposed based on the comparison of different filtering methods.The tests demonstrate that the proposed method has a good filtering effect that comprehensively considers the acoustic signal’s feature of nonlinear and non-stationary.Moreover,because acoustic signal has different energy features under different frequency,the thesis proposes a Hilbert-HuangTransform(HHT)time-delay localization algorithm based on cross-correlation time delay estimation and HHT.Experimental results show that the algorithm is able to enhance signal-to-noise ratio and then to improve the accuracy of leakage position on pipeline.Thirdly,design an acoustic monitor system for the pipeline leakage.The acoustic data acquisition system is designed based on STM3 2 that could realize the acquisition and transmission of sensor data.The software system is based on Lab VIEW,and the designed algorithms are transplanted onto the upper computer to implement the function of data filtering and leakage location.Meanwhile,other function modules are designed in the upper computer,including data reception,data storage and leakage signal analysis.Finally,the experimental platform of pipeline is set up to verify the effectiveness of the designed system.Knocking pipeline,drilling pipeline and leakage conditions are considered in order to obtain different data.The analysis results show that the designed system could detect pipeline abnormal in time and realize precise location.