Study On Fluid-Structure Coupling Vibration Characteristics Of Natural Gas Transmission Pipeline

The vibration of natural gas pipeline is often caused by the unstable flow characteristics and the change of fluid flow direction.In order to study the vibration of natural gas pipeline,the finite element model of natural gas pipeline was established based on fluid-structure coupling vibration theory,and modal analysis,harmonic response analysis and bidirectional fluid-structure coupling vibration response analysis of natural gas pipeline were carried out based on ANSYS Workbench platform.The research contents and main conclusions are as follows:(1)The modal analysis of the pipeline is carried out to study the changes of natural frequency and modal shape under different parameters(wall thickness,bending Angle,supporting mode).The results show that the wall thickness of the pipeline will have a great influence on the natural frequency and modal shape of the pipeline.With the increase of the thickness of the pipe wall,the equivalent stiffness of the pipe will increase,which will lead to the increase of the natural frequency of the pipe,and with the increase of the thickness of the pipe wall,the high-order vibration mode of the pipe will change from shell vibration to beam vibration.The increase of the bending Angle of the pipeline will lead to the increase of the low order natural frequency of the pipeline,and the modal shape of the pipeline almost does not change,except the deformation amplitude of the modal shape.Different supporting modes have important effects on the natural frequencies and modal shapes of pipelines,and the effects of different natural frequencies are different.The natural frequency of the pipeline is the minimum when the supporting mode 1 is adopted,and the natural frequency of the pipeline is the maximum when the supporting mode 3 is adopted.(2)The fluid-structure coupling modal analysis of the pipeline was carried out.The results show that the fluid-structure coupling effect will reduce the natural frequency of the pipeline,but because the density of the gas is small,the decline of the natural frequency of the pipeline is small,and the change of the vibration mode is small.The harmonic response of the pipeline is analyzed under a certain excitation frequency.The results show that the low order modes of the pipeline determine the vibration characteristics of the pipeline structure,which further verifies the modal analysis theory.(3)The influence of bending Angle and supporting mode on vibration response of pipe bend during constant pressure gas transportation is studied.The results show that the change of bending Angle and supporting mode will affect the vibration deformation amplitude and equivalent stress of the pipeline.When the pipe bending Angle is 60°,the deformation amplitude and equivalent stress at the pipe elbow are the largest.The comparison of the research results of different supporting modes shows that the deformation amplitude and equivalent stress at the pipe elbow are minimum when the supporting mode 3 is adopted.(4)The influence of pressure pulsation frequency and amplitude on the vibration response of pipeline is studied.The results show that when the pressure pulsation frequency is close to the natural frequency of the pipeline,the deformation amplitude at the elbow of the pipeline will increase greatly,so the pressure pulsation frequency of natural gas should be kept away from the first natural frequency of the pipeline to avoid resonance harm.When the pressure pulsation amplitude of natural gas increases,the vibration amplitude and equivalent stress of pipe elbow increase.The above study on fluid-structure coupling vibration characteristics of natural gas transmission pipeline provides a theoretical reference for the design and stable operation of natural gas transmission pipeline.