蒸汽射流直接接触冷凝相间结构及界面传输特性研究

The understanding of physical principles to accurately predict the dynamics of direct contact condensation (DCC) in a turbulent environment has major importance for a safe design of nuclear power plants. In this project, the phenomena and characteristics of interfacial mass and momentum transport of steam injected into subcooled water (e.g. the suppression pool) are studied in detail by using comprehensive advanced measuring techniques such as the high-speed camera, double-layer wire-mesh-sensor, particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF). Evolution principles and penetration length of the steam jet plume will be determined by analyzing the high-speed camera recordings that serve to improve model predictions. On the basis of data generated by the double-layer wire-mesh sensor, the three-dimensional reconstruction of the condensation regimes will be classified and the mechanisms of the transition between different regimes will be investigated. The three-dimensional condensation regime map for DCC will be established and the criteria for the transition of regimes will be set up with respect to the observed mechanisms. In order to understand the effect of these regimes, the relationship between the interfacial area and the condensation regime will be analyzed in detail. Turbulence characteristics will be measured by incorporating a synchronized PIV/PLIF system regarding the buoyant turbulent steam jet interacting with subcooled water, to obtain correlations between velocity and phase variations. The results are used to describe the mechanisms of DCC and models, based on the interfacial transport, will be developed and improved according to the obtained high-resolution data. The availability, applicability, and reliability of these models will be verified by making use of numerical methods like computational fluid dynamics (CFD). In conjunction with the experimental data, the development and the improvement of the models and their high fidelity results may support the safety analysis of nuclear reactors and offers the detailed insight into the dynamics of this important phenomena.

掌握湍流条件下蒸汽直接接触冷凝动力学特性的物理机理对于反应堆安全设计具有重要意义。本项目综合应用高速摄影、双层wire-mesh、PIV以及PLIF等先进测量手段，研究蒸汽直接接触冷凝过程中的界面传输特性；通过分析图像资料来确定羽流形状及穿透深度的演变规律和计算方法；利用双层wire-mesh测量数据重构三维冷凝图像，研究冷凝过程中的两相流型以及流型转变机理，建立分区流型图及流型转变准则，确定流型与相间界面面积的关系及影响相间界面面积的物理机理；利用PIV流场可视化技术对蒸汽射流引发的浮力射流流场进行测量，利用PLIF测量浮力射流区内的温度场，利用所得到的实验数据，确定湍流方程的特征参数，掌握蒸汽射流通过界面层的传输特性，建立可用于精细模拟的界面传输模型；采用CFD方法对直接接触冷凝机理模型的可用性、适用性和可靠性进行验证。为反应堆安全分析和直接接触冷凝现象的精细模拟提供支撑。

掌握湍流条件下蒸汽直接接触冷凝动力学特性的物理机理对于反应堆安全设计具有重要意义。本项目综合应用高速摄影、双层wire-mesh、以及PIV等先进测量手段，研究蒸汽直接接触冷凝过程中的界面传输特性和压力响应特性，总结得到冷凝换热系数经验关系式；通过分析图像资料来确定羽流形状及穿透深度的演变规律和计算方法，总结得到穿透深度的经验关系式；研究冷凝过程中的两相流型以及流型转变机理，建立基于蒸汽入口压力和水池温度的分区流型图及流型转变准则；利用PIV流场可视化技术对自由射流流场进行测量，总结得到射流场脉动强度、雷诺应力等湍流参数的分布规律；采用CFD方法对直接接触冷凝过程进行数值模拟，验证了冷凝模型的可用性、适用性和可靠性。本项目研究结果丰富了直接接触冷凝的现有相关理论，加深了蒸汽冷凝行为的认识，可为反应堆安全分析和直接接触冷凝现象的精细模拟提供支撑。本项目成果已发表SCI检索论文8篇，EI论文1篇，会议论文2篇，培养博士生2人，培养硕士生4人。项目投入经费60万，已支出46.8027万元，剩余经费13.1973万元。