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天然气在管道输送过程中,夹带的微小固体颗粒会对管道产生冲蚀磨损,进而引发管道失效。利用计算流体力学(CFD)软件能够模拟管内气固两相流流动预测壁面磨损量,但过往的(模拟)研究未能区分出磨损的不同阶段,仅采用单一的冲蚀磨损量预测模型。为此利用气固两相流流场结果,通过分界角β将磨损过程分为两个阶段:颗粒对壁面的冲击与颗粒对壁面的滑动或滚动。并将上述两个阶段采用不同的磨损量预测模型(Tulsa模型与疲劳磨损模型)作为用户自定义函数(UDF)加入计算软件中。计算结果表明:磨损量随着颗粒直径、颗粒密度、气体流速、弯径比的增加而增加。磨损量随不同影响因素的变化趋势,与分界角的变化趋势相似,证明了分界角是一个能综合评价弯管冲蚀磨损特征的参数。利用拉格朗日法分析了颗粒的碰撞特征,结果表明:二次碰撞位置更加靠近弯管出口,极易位于弯管焊缝的热影响区内,磨损情况将会加剧,甚至加速焊缝热影响区内的微裂纹扩展。
During the pipeline transportation of natural gas, the tiny solid particles entrained can cause erosion and abrasion on the pipeline, thereby causing pipeline failure. Computational fluid dynamics (CFD) software can simulate wall-to-wall gas-solid two-phase flow in the pipe to predict the amount of wall wear. However, previous studies failed to distinguish the different stages of wear, using only a single erosion wear prediction model. For this reason, the gas-solid two-phase flow field is used to divide the wear process into two phases by the boundary angle β: the impact of particles on the wall and the sliding or rolling of the particles on the wall. In the above two phases, different wear prediction models (Tulsa model and fatigue wear model) were added to the calculation software as user-defined functions (UDFs). The calculation results show that the amount of wear increases with the increase of particle diameter, particle density, gas velocity and the ratio of diameter to diameter. The variation trend of wear amount with different influencing factors is similar to that of the dividing angle. It is proved that the dividing angle is a parameter that can comprehensively evaluate the characteristics of elbow erosion. The collision characteristics of the particles were analyzed by Lagrangian method. The results show that the location of the secondary collision is closer to the outlet of the elbow, which is easily located in the heat-affected zone of the elbow weld. The wear condition will be aggravated and even accelerated Affect the area of microcrack expansion.