Erosion Characteristics Of Liquid-Solid Two-Phase Flow On Elbow

Erosion is one of the important reasons for the failure of oil and gas pipelines.The thinning,cracking and even perforation of the pipe wall brought by it has a serious impact on the efficiency and safety of oil and gas production.As one of the important components to ensure the continuous and complete pipeline,the elbow is special because of its special structure,the fluid movement here is relatively complicated,it is more susceptible to erosion damage than the straight pipe,and the damage is often dozens of straight pipes Times.The factors that cause elbow erosion are complex and diverse.The degree of erosion damage is different at different flow rates,different concentrations and different bending diameter ratios.The degree of erosion damage is also different at different angle sections and walls at different locations.To understand the different situations and the extent of erosion damage at various locations,which is of great significance for effectively preventing pipeline failure and ensuring the safe and efficient production of oil and gas.Based on the self-designed experimental section of Plexiglas elbow,a cyclic flow elbow erosion test pipeline was set up using a jet test stand.Designed different flow velocities(1m/s,2m/s and 3m/s),different solid phase particle concentrations(5%,10% and 15%)and different bending ratios(R/D= 2.5,R/D= 3.5And R/D=5)erosion experiment of liquid-solid two-phase flow on elbows.The weight change method was used to compare the mass change of samples at different angle sections and different positions.It was determined that the weight loss of the samples on the side wall and the outer arch side increased with the increase of the angle,and increased with the increase of the flow velocity and concentration.It increases with the increase of the bending diameter ratio within a certain range;part of the weight loss of the specimen on the inner arch side has increased,It is thought to be due to corrosion on the sample surface,the impact on the side of the inner arch was lighter and the corrosion products could not be completely washed out.In addition,the surface morphology of the sample was analyzed with an electron microscope,and scratches at small angle sections and etch pits at large angle sections were observed,and the increase in scratches and etch pits with increasing flow velocity and concentration.The experiments were compared and verified by numerical simulation calculations,and the erosion of the curved pipe by the liquid-solid two-phase flow at different flow rates,different particle concentrations,and different bending diameter ratios was simulated.The distribution characteristics of the flow field in the elbow and the trajectory of the solid particles were obtained.As a result,the collision of surface particles on the wall occurred mainly on the side wall surface and the outer arch side wall surface.The secondary flow and the mainstream superimposed in the elbow caused the junction between the outlet of the pipe section and the downstream straight pipe section becomes the most severely eroded part.Then,the flow characteristics under different speeds,different concentrations and different bending diameter ratios are analyzed,and the maximum erosion rate corresponding to different conditions is calculated.The erosion law of liquid-solid two-phase flow on the bent pipe is obtained.Finally,the experiments are compared with the simulation analysis,the differences and similarities between them are determined,and give some protection suggestions.