液固两相流对弯管的腐蚀磨损耦合破坏机制研究

Corrosive wear in multiphase flow condition has increasingly become one of the major hazards in oil and gas fields. Pipelines, especially elbow sites in liquid-solid two phase flow often subject to corrosive wear and face huge risk of localized corrosion failure. Due to the limitations that the traditional corrosion test can provide only the average electrochemical information of the whole electrode, coupling uncertainties of hydrodynamics and corrosion kinetics, and difficulties of the elbow injury monitoring, the local failure mechanism of elbows by interaction of corrosion and wear is still in talking. Therefore, combined with numerical simulation, weight loss method of small samples and the wire beam electrode technique are employed to monitor the corrosion, wear and the interaction contribution to the total damage in different regions of the elbow quantitatively. The hydrodynamics model is established, and the influence on the corrosion protective film is assessed. The failure mechanism of elbows by interaction of corrosion and wear is studied, and the corrosion-wear kinetics model of the elbow in liquid-solid two phase flow is established. This study belongs to the interaction scientific issues of the hydrodynamics and corrosion kinetics, and it is with important value and scientific significance to clarify the corrosive wear failure mechanism of the elbows in theory and provide guidance for the pipe design and effective anti-corrosion measures development in corrosive wear environment.

多相流腐蚀磨损越来越成为油气田的主要危害之一，管线内部尤其是弯管部位常受到液固两相流腐蚀磨损而面临局部腐蚀失效的巨大风险。由于传统腐蚀实验技术利用整体电极仅能提供平均电化学信息这一局限、流体动力学和腐蚀动力学的相互耦合的不确定性以及对弯管损伤监测的困难，目前对液固两相流作用下弯管的局部破坏机制仍然缺乏深刻的认识。因此本课题将两相流数值模拟与小试样失重法、丝束集成电极法相结合，定量研究磨损、腐蚀及其耦合作用在弯管不同微区损伤的贡献，分析建立弯管内壁流体动力学模型并评价流体动力学对腐蚀保护膜的影响，研究液固两相流对弯管腐蚀磨损耦合破坏机制，建立液固两相流对弯管腐蚀磨损动力学模型。该研究属于流体动力学和腐蚀动力学之间相互耦合的科学问题，对于在理论上弄清弯管的腐蚀磨损耦合破坏机制，在实践上指导腐蚀磨损环境下多相流管道设计、发展混输管路有效内防腐措施具有重要意义。

多相流腐蚀磨损越来越成为油气田的主要危害之一，管线内部尤其是弯管部位常受到液固两相流腐蚀磨损而面临局部腐蚀失效的巨大风险。本课题结合油气田管道输送中存在的腐蚀磨损危害控制的应用需求，提出进行弯管液固两相流场中腐蚀磨损耦合机制的实验与理论研究，通过自行设计的管流式弯管腐蚀磨损测试装置，采用实验测试与数值模拟相结合的方法研究了液固两相流条件下90°水平弯管的腐蚀磨损特征。采用失重法以及腐蚀电位监测、电化学阻抗谱测试、表面分析等方法，研究了不同含砂量、不同温度、不同流速工况下弯管不同微区腐蚀与磨损损伤特征；通过CFD数值模拟计算，研究了弯管内壁流体流型分布规律；通过纯磨损、纯腐蚀及腐蚀磨损实验，定量分析了弯管不同局部区域腐蚀、磨损以及其交互耦合作用在弯管损伤中的贡献，确立流体动力学和腐蚀动力学耦合作用下弯管的损伤机制。结果表明，随着含砂量、温度、流速的增加，弯管腐蚀磨损速率增大，腐蚀磨损最严重的位置在水平弯管出口段的内侧底部及外侧部分；流体从直管进入弯管后，受到弯管影响和管壁约束形成旋转流动，由于离心力的影响和流体流动的连续性，弯管外侧内壁面附近的流体经过上下壁面被迫向内侧壁面附近流动，因此在弯管内产生涡旋，并且按一定方向旋转，形成二次流。在弯管出口段，二次流强度较高，弯管内壁剪切应力也较高；冲刷与腐蚀交互作用是引起金属材料损伤的主要原因，机械冲刷过程与电化学腐蚀过程相互促进，机械冲刷在腐蚀磨损过程中起到主导作用。本课题揭示了弯管不同微区腐蚀与磨损损伤特征差异，确立了液固两相流对弯管腐蚀与磨损耦合破坏机制，在实践上指导腐蚀磨损环境下多相流管道设计、发展混输管路有效内防腐措施具有较好的科学研究意义与应用价值。