面向浮动平台的小通道内两群气泡界面分布与输运特性研究

The Floating Nuclear Power Plant platform applying small modular reactor technology is one of the most important ways to solve the power shortage problem in marine development. The variable motion conditions of the offshore platform can severely affect the mass and energy transfer process though the interfaces of two-phase flow in the reactor core, resulting in changes in the thermal-hydraulic characteristics of nuclear reactor system. Therefore, this project will conduct an in-depth research on interfacial distribution and transport characteristics of two-phase flow in a small diameter pipe under both static and rolling conditions. The experimental study on adiabatic air-water two-phase flow in a vertical small diameter pipe under static condition will be carried out extensively using the state-of-art miniaturized four-sensor conductivity probe, which can fully reveal the interfacial structure distributions and development characteristics from bubbly to churn flow. Through a comprehensive analysis on the interaction mechanisms between two-group bubbles, the two-group interfacial area transport equation for two-phase flow in a vertical upward small diameter pipe will be established and the characteristics of interfacial transport will be mastered. The dynamic two-phase flow experiment will be conducted on a rolling platform. The variations of instantaneous local interfacial parameters as well as its influencing factors will be obtained. The interfacial area transport equation applicable for two-phase flow under rolling conditions will be proposed by identifying the impact mechanisms of structure motion on the interfacial area transport process. The research achievements of this project are essential to accurately predict the two-phase flow phenomena in the reactor core and to improve the two-fluid model, which is of great significance for the safety operation of nuclear reactor system on the offshore platform.

采用小型模块化反应堆技术的海上浮动核电平台是解决海洋开发过程中能源短缺问题的重要途径。但复杂多变的海上平台运动工况会严重影响堆芯流道内两相流通过相界面的质能传递过程，进而改变系统热工水力特性。因此，本项目拟对静态及摇摆条件下小通道内两相流的相界面分布与输运特性开展深入研究。采用小型化四探头电导探针技术进行竖直静止小通道内空气-水两相流实验研究，充分揭示泡状流到搅混流区域两相界面结构的分布和发展特点；全面分析两群气泡间的相互作用机制，建立适用于竖直向上小通道的两群界面浓度输运方程，掌握两相流界面输运特性；利用摇摆台开展动态两相流动实验研究，获取摇摆条件下瞬态局部界面参数的变化特点及影响因素；揭示多运动场耦合对界面输运过程的影响机理，建立摇摆条件下的两相流界面输运模型。项目研究成果可为准确预测海上平台堆芯流道内的两相流动现象并完善两流体模型奠定基础，对保障反应堆系统安全运行具有重要意义。

竖直小通道内的两相流动是浮动核电站反应堆系统内的重要现象，直接影响反应堆系统的热工水力特性。本项目对静态及外加动载条件下小通道内气液两相流相界面分布及输运特性展开深入研究。主要内容包括：（1）对竖直小通道内泡状流至弹状流区域两相局部界面参数包括空泡份额、界面浓度、气泡直径等及截面平均界面参数的分布和发展特点进行了广泛研究，建立了实验数据库；（2）探究通道尺寸对气泡作用机制的影响，构建了竖直小通道内一维两群界面输运模型，揭示了小通道内两相流界面输运机理；（3）引入外部动载作用对两相流的影响，建立了静态及动态条件下泡状流区域小通道内气液两相流计算模型。本项目研究相关工作可用于完善两流体模型，为浮动反应堆系统安全分析提供支持。

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