In a natural gas transmission system,when welding defects at the elbow are considered,the flow field changes caused by the different structural characteristics will lead to different erosion characteristics at the elbow.The Computational Fluid Dynamics-Discrete Phase Model(CFD-DPM)method has been used to study the media flow characteristics and erosion laws at an elbow without an internal defective edge weld,an elbow with an external defective edge weld and an elbow with an internal defective edge weld under the influence of different particle pa-rameters,bend guides,defect heights and particle incidence angles.The results show that:①There is a secondary flow phenomenon in the elbow,and the velocity distribution is distorted.The curvature of the velocity distribution curve of the elbow with the external defective edge weld is larger,and the secondary flow effect is the most obvious.②The effect of fluid velocity on erosion rate is the largest,having a power exponential function,followed by mass flow rate,which is a linear function,and particle size,which is approximatively a linear function.③Severe erosion wear areas are formed in the elbow of the bend with the external edge defect.In contrast,the erosion effect of the internal defective edge weld is similar to that of the bend without a defective edge weld,which both only have one serious erosion area.④When the flow direction of the vertical pipe is the same,the maximum erosion rate of the"H-V"guide pipe is greater than that of the"V-H"guide pipe,and the erosion rate of the external misaligned weld pipe is a maximum for different bend guides.⑤The maximum wear position on the outermost side of the elbow changes with the height of the defect side.The inner wall of the bend will form a second area of serious erosion wear at a certain height.The higher the height of the defect side,the greater the erosion rate on the outermost side of the bend.⑥The particle incidence angle will change the erosion effect of the bend,and the influence degree should be analyzed in combination with the length of the inlet straight pipe and the particle motion state.
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