多场耦合作用下高含水原油集输管道腐蚀演变机理研究

Droplet deposition is easy to occur in the gathering and transportation pipeline of crude oil with high water cut, leading to the occurrence of flowing hydrops. Subsequently, the corrosion problem in multiphase flow is induced under the coupling action of flow field, concentration field and electrical field. As a result, the long-term safe service of crude oil pipelines is seriously restricted. Multiphase flow corrosion is a complicated issue involving a series of physical and chemical processes in different scales, such as multiphase flow, multicomponent mass transfer and interface electrochemical reactions. These complicated coupling processes pose a challenge for the investigation on corrosion evolution mechanism. Firstly, the project experimentally investigates the interrelationship between droplet kinetic behavior and hydrops, in order to explore the interface development law and internal flow characteristics of the flowing hydrops. The in-situ online test platform for flow corrosion is built based on the flow characteristics of the flowing hydrops, by which the local chemical characteristics and electrochemical bahevior, such as the distribution of species concentration, potential and corrosion current density, being a function of exposure time, is investigated for revealing the influence mechanism of flow field characteristics within the hydrops on the electrochemical reaction kinetics at metal/solution interface. Furthermore, the corrosion dynamics model based on the multi-physics coupling is established, in order to explore the interaction among flow, interface reactions and mass transfer. The coupling action mechanism of these processes on the corrosion growth kinetics is analyzed. As a result, the temporal and spatial evolution mechanism of corrosion behavior is revealed, such as corrosion rate and interface morphology. The project contributes to the development of multiphase flow corrosion theory, and provides theoretical support for pipeline corrosion prediction and optimization operation. Therefore, the long-term safe operation of pipelines can be effectively guaranteed.

高含水原油集输管道极易发生水滴沉积形成流动的积液，进而诱发流场-浓度场-电势场耦合作用的多相流腐蚀问题，严重制约管道的安全持久服役。多相流腐蚀包含多相流动、多组分传质以及界面电化学反应等不同时间-空间尺度的物理化学过程，这些过程之间的复杂耦合作用对腐蚀演变机理研究提出了挑战。本项目首先探究液滴动力学行为与积液变化过程的内在联系，获取积液界面发展规律及内部流场特性；基于积液流场特性，建立流动腐蚀在线原位测试平台，分析不同时刻的组分浓度、电位、腐蚀电流密度分布规律等化学特征与电化学行为，阐明积液内部流场特性对金属/溶液界面处电化学反应动力学的影响机制；进而建立多场耦合腐蚀动力学模型，探究流动、界面反应、传质之间的交互作用及其对腐蚀过程的耦合影响机制，揭示腐蚀速率、界面形貌等腐蚀行为的时空演变机理。该项目有助于发展多相流腐蚀理论，为管道腐蚀预测和优化运行提供理论支撑，保障管道长周期安全运行。

高含水原油集输管道内水滴沉降形成积液后极易诱发严重的腐蚀损伤，在多相流腐蚀损伤的动态演变过程中，不同时空尺度的多相流流场、多组分传质以及界面反应之间存在着复杂的耦合关系，对腐蚀演变动力学机理的研究提出了挑战。本项目基于多相流动力学、传质学、电化学及动电学基本原理，针对多相流腐蚀过程中水滴微观行为与积液界面演化过程的数理联系、流场-浓度场-电势场耦合特性对腐蚀多尺度演变过程的作用机制两个关键科学问题开展了深入研究。首先基于表面能平衡理论、液滴动力学特性，建立了主流湍动能、积液界面表面能以及水滴表面能之间的能量传递与积液界面变化过程的内在联系，揭示了积液发展过程中相态分布不均匀性的特征参数与主流速度、含水率、油品物性的定量数理关系，建立了多相流条件下流动积液形成的临界准则，获取了多相流条件下积液界面发展规律及内部流场特性，为研究多相流腐蚀提供了关键的流场特征；在此基础上建立了腐蚀电化学在线原位测试平台，利用动电位极化、电化学阻抗谱方法系统研究了复杂积水中的动态腐蚀行为，分析了数值模拟难以获取的电极极化动力学信息以及电极界面结构信息，揭示了积液化学环境对电极反应、腐蚀产物膜沉积过程、钝化过程的影响机理，形成了积液条件下的界面反应动力学机制；进而建立了流场-浓度场-电势场耦合的腐蚀动力学模型，解决了腐蚀模型中流场耦合求解的难题，实现了腐蚀行为中物质传输过程、化学反应与金属/溶液界面处电化学反应的定量描述，获取了流动特性、传质过程、界面反应对腐蚀行为的耦合作用机制，揭示了腐蚀行为的时空演变机理，更真实地描述了腐蚀演化过程从而实现了更准确的腐蚀速率预测，最终完成基于多场耦合反应输运理论的多相流腐蚀演变机理研究。通过本项目丰富和发展了多相流腐蚀理论，建立了多相流管道腐蚀预测体系，为管道腐蚀防护和优化运行提供理论依据，对于保障管道的长周期安全运行有着重大意义。