Estimation Of Stress Wave Velocity In Natural Gas Pipeline Leakage

High and intermediate pressure gas pipeline is an important part in the construction of urbanization, when the gas pipeline is damaged by natural or man-made factors,different degrees of leakage occurs, because of the pipeline its own and the external environment factors’ interference, the transmission speed of the leakage signal is not consistent, which directly affects the precision of the pipeline leakage location. Therefore,it is important to accurately estimate the propagation velocity of stress wave based on the characteristic of collected stress wave signal, which plays an important role in pinpoint pipeline leak location. Based on the study of the mechanism of the stress wave, through the software ANSYS finite element model is established. First of all the stress wave generation mechanism at different apertures and different tube pressure was studied by numerical simulation; Then analyzing the wave propagation velocity and its amplitude-frequency characteristics under different conditions in the pipe model and at different location; Finally, measuring the speed of the collected stress wave, and comparing with the propagation speed of the simulation signal in the pipeline model, and the reason of the difference is analyzed. The main work of this paper is as follows:Firstly, using ANSYS Workbench to get the model of the pipeline with different leakage aperture, through ANSYS Fluent simulation module to get the pressure fluctuations near the pipeline hole under different pressures, export pressure load data for subsequent structural analysis. By ANSYS APDL modules analyzes generating mechanism at the condition of different leakage aperture, different stress waves leaking pipe pressure. Then according to the propagation characteristics of the stress wave, using ANSYS simulation software, the simulation of different forms of stress wave propagation on the pipe body is carried out, observing the amplitude frequency characteristics and the change of the wave velocity after the propagation of different distances; According to the guide wave theory, deducing the dispersion equation in hollow cylindrical shell, taking theexperimental pipe parameters into the equation, and get the dispersion curves of the pipeline obtained by Matlab simulation.Secondly, because of the non-stationarity of the gas leakage signal, in this paper, a new method of estimating stress wave velocity is put forward: After decomposing the stress wave, calculate the entropy of each PF, select the PF with largest entropy as main component, do cross-spectral analysis with main component to obtain the most relevant frequency, combine with the signal dispersion curve to obtain the stress wave theory propagation velocity.Finally, according to the method in this paper, processed the collected actual stress wave in two different situations, which are the same aperture leakage with different inner pressure, and different leakage aperture with the same tube pressure, then estimating the propagation velocity of stress wave in different conditions, compares them with the theory of wave velocity difference, at last, under the same conditions, the theory of wave velocity changing trends in conformity with the actual wave velocity change trend.