Analysis And Application Of Fluid-structure Interaction Vibration Characteristics Of High-pressure Long-distance Pipelines

Long-distance pipelines are widely used in the process of oil and gas transportation.Due to the control changes of ground equipment,the sudden change of pipeline cross-section,and the opening and closing of pipeline valves,the fluid in the pipeline is in an unsteady state,resulting in coupled vibration between the pipeline and the fluid.Strong vibration can cause pipeline rupture or even failure,and cause pipeline safety problems.Therefore,the study of pipeline Fluid-Structure Interaction vibration is of great significance to the safe operation of pipelines.Pipeline vibration is a relatively common problem.This article takes long-distance pipelines as the research object,considers the Poisson effect,and uses one-dimensional unsteady flow as the basis.The fluid continuity equation is corrected by using the modified water hammer pressure and water hammer velocity.The "classical water hammer theory" theory takes into account the interaction between structure and liquids,and forms an improved axial 4-equation model with simplified fluid momentum equations,pipeline motion equations and physical equations.Based on and on this basis,the pipeline fluid-structure Interaction finite element method was revised,and the fluid-structure Interaction vibration simulation of long-distance pipelines was carried out using ANSYS Workbench software.The flow field characteristics and the pipeline structure field characteristics were discussed.Through the above research,the following conclusions were obtained:(1)Based on the Fluid-Structure Interaction finite element theory,with straight pipes and elbows as the research objects,the flow characteristics of the pipeline are calculated,and the flow field distribution on the YOZ surface of the middle section of the pipeline is obtained.For straight pipes,the results of calculating the flow field distribution in the pipe under different parameters(velocity,pressure,pipe length,pipe diameter)show that the above parameters have little effect on the flow field distribution in the pipe;for curved pipes,different parameters(velocity,The results of the flow field distribution in the lower pipe show that:(1)With the increase of the flow velocity,the natural frequency value of the pipe does not change much,ranging from 79 Hz to 728Hz;the maximum flow velocity in the pipe appears near the elbow;the maximum pressure appears at the outlet section and Near the elbow,and with the increase of the flow rate,the pressure accumulation phenomenon at the outlet section of the elbow is significantly reduced;(2)With the increase of pressure,the natural frequency of the pipeline increases,but the increase is small.The maximum flow rate value and its position are not greatly affected.Pressure changes will not affect the velocity distribution of the liquid in the pipeline.(2)Based on the Fluid-Structure Interaction finite element theory,the structural field of the Fluid-Structure Interaction vibration in the tube is analyzed.The fluid-structure Interaction vibration response under different parameters(wall thickness,pipe length,pipe diameter,flow velocity,pressure)is calculated.The results show that the influence of wall thickness,tube length,tube diameter,pressure,and velocity on the Fluid-Structure Interaction of the pipeline decreases in turn.As the wall thickness increases,the natural frequency decreases,and the amount of deformation decreases;the pipe length increases,the natural frequency decreases,and the pipe deformation increases;the pipe diameter increases,the natural frequency increases,and the pipe deformation decreases,but the overall change trend is smaller;As the pressure increases,the natural frequency increases;speed changes have no major influence on the natural frequency,flow field distribution,and pressure distribution of the pipeline.(3)Perform modal analysis and harmonious response analysis on the pipeline to study the operation of the pipeline.Through modal analysis,it is found that the fluid-structure interaction will deform the pipe body.As the order increases,the natural frequency and deformation both increase.Through harmonic response analysis,it is found that to avoid resonance,attention must be paid to the displacement in the X direction,to avoid first-order resonance and second-order resonance,and X-direction constraints can also be imposed on the pipeline.In addition,the500 mm position on both sides of the pipeline The fixed constraint can achieve a good antivibration effect.The above research results can provide references for pipeline selection and service conditions,optimize structural design parameters,optimize construction plans,and prevent pipeline failure due to vibration.