Experimental Research And Numerical Simulation On Erosion-corrosion Of Elbow In Liquid-solid Two Phase Flow

Erosion-corrosion usually occurs on the pipelines for oil and gas gathering and transferring,because the multi-phase flow,consisting of oil,gas,water and sand,is unstable,which could easily lead to erosion-corrosion and effect the life span of the system.These years due to the frequent occurrence of pipeline damage accidents of erosion-corrosion,erosion-corrosion gradually became one of the main hazard,especially in elbow pipeline.Erosion-corrosion happens in the process of scour and corrosion.Elbow is one of the weakest part of the gathering and transferring pipeline,but due to the limit knowledge experts are still on their way working out the influence patterns of erosion-corrosion in elbow pipe.The research means a lot to the improvement of safety factor and would guide the design of anti-corrosion structure and ensure the safety of operation.This paper presents the study of erosion-corrosion behavior of horizontal elbow pipe in liquid-solid two-phase flow and mainly presents the study of influence of mechanism factors on erosion-corrosion behavior of horizontal elbow pipe in liquid-solid two-phase flow by adopting those methods such as weight loss method,electrochemical method,morphological observation method and numerical simulation.At first,by using the pipe-flow experimental device,total erosion-corrosion rate quantitatively calculated by the weight loss method.The open circuit potential and electrochemical impedance spectroscopy,measured by the electrochemical workstation,dictated that electrochemical corrosion has an important role in the hole erosion-corrosion behavior.The object of the study was observed after the erosion-corrosion experiment,by using optical microscope and scanning electron microscopy(SEM).Then using the computational fluid dynamics software,did some numerical simulation by considering the different experimental condition,finally in order to develop the study,compared the numerical simulation results with experimental data.Those comprehensive method results can determine that the serious areas of the erosion-corrosion mainly exist on the sidewall at the bottom,as well as the outermost side of outlet section of the horizontal elbow pipe.The relevant conclusions,drawn by studying the effect of the particle velocity on the erosion-corrosion behavior of horizontal elbow pipe in liquid-solid two-phase flow,show that erosion-corrosion rate of horizontal elbow pipe in liquid-solid two-phase flow increased with the increase of particle velocity within a certain range,the erosion-corrosion became more serious.Under the turbulence state,shearing stress on the wall of the elbow increases with increasing particle velocity,which leads to a higher erosion-corrosion rate and aggravates erosion-corrosion of the elbow.The particle velocity is positively correlated with erosion-corrosion rate of the horizontal elbow in liquid-solid two-phase flow.This thesis also presents a study on the effect of particle size on erosion-corrosion of the horizontal elbow in liquid-solid two-phase flow.The results show that erosion-corrosion rate of the horizontal elbow dose not exactly increase as particle size increases within a certain range.When inertia force of particles plays a leading role,erosion-corrosion rate increases as particle size increases.However,when carry-over effect of secondary flow on particles is dominant,erosion-corrosion rate does not increase with particle size.It can be concluded that there exists a critical particle size for the influence of particle size on erosion-corrosion of the horizontal elbow in liquid-solid two-phase flow.