Research On The Theory And Method Of Pipeline Damage Detection Based On Acoustic Emission

As an efficient,clean and convenient transportation method,pipeline transportation has been widely used in energy transportation such as oil and natural gas.As of today,pipeline mileage has been growing rapidly.However,because it is located in every corner of the city and is vulnerable to natural disasters,disrepair,man-made damage and other factors,the safety hazards caused by leakage are very huge.In order to eliminate this hidden danger,it is necessary to understand the diffusion mechanism of gas leakage and to locate the leakage source in time.Therefore,this thesis intends to explore and research from the following aspects:First,the jet theory of leakage and the basic equation of gas flow are studied,FLUENT software is used to simulate the diffusion of overhead and buried pipelines under the influence of large-hole leakage,small-hole leakage and different factors,so as to understand the law of gas diffusion and the diffusion mechanism,so as to determine the safe concentration range in time when gas leakage is encountered.Secondly,in order to offset the influence of the transmission path on the pipeline leakage signal,the improved MCKD method is used to reduce the noise of the pipeline leakage signal and improve the signal strength.And for the selection of MCKD parameters.In this thesis,the method of comparing the signal-to-noise ratio is used to determine the parameters.The larger the signal-to-noise ratio,the better the parameter selection.Comparing with the minimum entropy deconvolution(MED)algorithm,the effectiveness of the MCKD method for pipeline leakage signal processing is verified.Then,using the VMD decomposition method to decompose the collected signal,the signal can be decomposed into sub-signals of different frequencies,and the accurate separation of the signal can be achieved,which can well highlight the local details of the signal.The effect of noise reduction on pipeline leakage signals.In this paper,the correlation coefficient between the modal component and the signal before decomposition is used to determine the magnitude of the value.The optimal solution of the penalty factor can ensure the accuracy of signal reconstruction.The selected value is used as a known parameter.Compared with the kurtosis value of the penalty factor from 1 to 5000 in steps of 100,the maximum kurtosis value is selected.is the optimal penalty factor.The Hilbert transform is performed on the signal after VMD decomposition and IMF reconstruction for envelope analysis.The results show that the method can effectively highlight the impact components of the signal and achieve the effect of noise reduction.Finally,the MCKD and VMD methods are combined to double denoise the signal.The MCKD method is used as a pre-filter to suppress and eliminate the noise signal on the transmission path,so as to improve the signal-to-noise ratio of the leaked signal.The denoised signal is analyzed in depth by using the VMD method,and the recombined signal obtained after decomposing is subjected to envelope analysis,which can effectively realize the denoising of the signal.The research content in this thesis can simulate the risk of pipeline leakage under different factors from the stage of pipeline design and construction,and reduce the harm caused by the natural environment in the stage of site selection.The noise reduction processing of the leakage signal can well reflect the leakage impact component and can be used to locate the leakage source.