深海油气管道气液段塞流无相变冷却过程传热与流动机理研究

The petroleum exploitation in deep sea offshore fields is dependent on the long pipelines located on the sea bottom to transport the natural gas and crude oil safely and efficiently. During transportation by many pipelines, the mixture of oil and gas produced from wells with high temperature is cooled by the cold sea water and the gas hydrate and wax deposition blockages might occur and the field will be shut down. Therefore the knowledge of heat transfer in cooling process of slug flow commonly encountered in the oil-gas pipeline is very important for offshore oil and gas production. This project is planned to experimentally investigate and model the non-boiling heat transfer and hydrodynamic characteristics of gas-liquid slug flow in cooling process in deep sea oil-gas pipelines. Test facility will be designed and constructed to study heat transfer of gas-liquid two-phase flow in cooling process of deep water environment. The methods and techniques to measure the phase interface of oil and gas will be developed. The hydrodynamic and interfacial characteristics of liquid slug and elongated bubble, such as the void fraction, the thickness of liquid film, the length, the frequency and the pressure drop, and the local and the ensemble heat transfer coefficients along the circumference and axis of pipe will be measured and analyzed. A model to predict the hydrodynamic and heat transfer parameters simultaneously will be developed based on the slug tracking model. Therefore a reliable method can be provided to calculate the temperature profile for flow assurance issues. This project is crucial for economical design and optimized operation of deep sea oil-gas pipelines and very important for completing the system of multiphase flow thermophysics.

深海石油天然气的开采依赖长距离的海底油气混输管道的安全高效输送。油井生产的气液混合物在输送过程中被海水冷却降温会生成蜡或水合物堵塞管道造成停产。因此气液混合物在海底混输管道常见的段塞流型下的冷却传热规律非常重要。本课题对海底管道段塞流型无相变被冷却时的传热特性及水动力特征参数进行实验测量与模型构建。建造可实现深海环境的气液两相流冷却换热实验装置，开发油气相界面测试方法与技术，获取冷却条件下液塞与气弹区的含气率、液膜厚度、长度、频率、压降等相界面结构以及水动力参数分布与管道周向、轴向局部和总体平均传热特性的影响规律。探索结合段塞流跟踪模型，建立流动与传热机理统一的预测模型，实现对混输管道冷却传热过程与段塞单元水动力参数的同步预测，为流动安全问题提供基本的温度场预测方法。本研究对于指导深海管道的设计与运行管理、完善多相流热物理学体系具有重要意义。

我国南海蕴藏着丰富的深水油气资源，亟待开发。海底混输管线在深海海底低温环境中会快速散失管内气液流体热量，从而引起水合物、蜡、沥青质等固态物质的沉积。水平及倾斜管内的气液沿管道周向分布不均造成局部传热特性不同，因此对于海底管道两相流冷却时的流动换热需要深入研究。.研究了空气—水、空气—油等两相流相界面测试方法，开发了适用于油气测量的双凹面电容电极相界面检测技术。提出了测量液塞速度与长度等参数的电容差值测量方法。研究了气液两相流动的声发射测试方法，开发了声发射采集与参数实时处理程序。揭示了段塞流的液塞区声发射信号的产生机制，建立了含气率的测量模型。提出了基于声发射测量的气液段塞流液塞区判别及参数检测方法。.在冷却换热实验系统上完成空气-水、空气-油的两相段塞流冷却传热及流动实验。采用电导探针、电容探针等测试手段测量段塞流的流动参数，测量液塞运动速度、持液率、液塞长度、频率等参数的规律。绘制了白油-空气的流型图。获得了冷却与绝热条件下气液段塞流多种水动力特征参数的测量数据。同时实验研究了气液界面的起塞过程，对液塞的发展演化过程进行了研究.研究了油气和空气-水段塞流的流动与传热参数，明确了冷却条件下段塞流对流换热系数随两相流气液表观流速、压降、液塞速度、液塞长度、液塞频率、液塞持液率、液膜持液率的变化规律。建立了适合于多种介质的段塞流型冷却换热的实验关联式。.基于界面捕捉方法建立了统一的水平管气液两相流三维计算模型，对不同工况下的段塞流自然发展过程进行模拟，揭示了发展中液塞和充分发展液塞的运动特征和压力场、速度场分布等规律。.通过分析段塞流的三维流动和冷却换热机理，在段塞流跟踪模型的基础上结合换热机理模型，建立了能够准确预测段塞流冷却换热的机理模型，开发了流动与传热参数同步计算的段塞流数值计算软件。本研究对于多相流热物理理论的发展和海洋油气生产系统的设计运行具有重要的学术意义和应用价值。