Research Of Using Passive Wave Technique In Pipeline Structure Leakage Monitoring

At present,pipeline transportation has the advantages of low cost,high efficiency,low pollution,continuous process,small external influence and automatic control,etc.,which makes pipeline transportation widely used at home and abroad,especially occupying a very important position in natural gas,crude oil,refined oil transportation.However,with the increase of service time of pipeline transportation system,the complex environment around pipeline structures and the particularity of pipeline transport material make pipeline transportation face the risk of leakage or explosion in operation and maintenance stage,which might bring huge losses to the natural environment,national economy and people's lives and property.Therefore,it is very important to monitor the leakage of pipeline structures.During the leakage process a weak passive wave will be generated and the propagation of leaky waves is very complex.The pipeline leakage can be effectively monitored by the passive wave technology,so the pipeline leakage monitoring using passive wave technology has been paid more and more attention.To monitor the leakage of pipeline structures,the emphasis focuses on studying the propagation law of acoustic wave and accurately evaluating the location of leakage sources.However,there are few such researches at present,and many problems need to be solved.In this paper,the aim is to propose a relatively precise method to locate the leakage sources of pipeline structures using a piezoceramic passive wave method through the combination of theoretical analysis,numerical simulation and experimental verification.The main contents are concluded as following:Firstly,the generation and propagation of leaky sound waves are introduced,and the propagation characteristics of leaky acoustic waves in pipes are theoretically analyzed,and then the dispersion equation of leaky acoustic waves propagating in pipes is deduced.The leakage acoustic dispersion equation is numerically solved using MATLAB,rendering the group velocity dispersion curves.According to experiments of the leakage sound frequency measurement and the control group velocity dispersion curve,the leakage acoustic wave propagation velocity in pipes is evaluated,and the group velocity can be characterized in the pipeline leakage acoustic wave propagation velocity.Secondly,the time of flight(TOF)method is applied to locate the leakage source in pipeline structures.The ABAQUS software is used to the research the method of leakage source localization in order to clarify the main influencing factors and laws,focusing on the research of the leakage wave time difference arriving the two different PZT sensors.The numerical simulation method is used to validate the feasibility of using the TOF method to locate the leakage source and the effectiveness of applying the cross-correlation function to determine the wave arriving time difference.The dynamic displacement is used to replace the leakage shock at the leakage hole to simplify the numerical simulation model,and the piezoelectric elements are used to replace the PZT sensors,realizing the numerical simulation and experimental analysis of data acquisition with data into electrical signals.Numerical simulation results show that the correlation function analysis method can accurately determine the time difference values,and the TOF location method can accurately locate the source of the leak location,which lays a theoretical foundation for the experimental validation and engineering application of the leakage localization.Finally,an experiment of using the passive wave technology to monitor the leakage of pipeline structures is performed to validate the efficiency of the proposed method.A convenient and effective test system for different propagation distances and different water pressures is established by using PZT sensors as the receiving device.The comparison between the numerical simulation results and the experimental analysis ones shows that the passive monitoring method of pipeline structure leakage using passive wave technology has good feasibility and accuracy.