钠冷快堆ALIP核主泵磁流体瞬态特性与流动稳定性研究

The control of flow stability in large rated flow rate ALIPs is the essential problem in the design and manufacture of nuclear coolant pump of the sodium-cooled fast reactor (SFR) and the study of the flow stability of magnetohydrodynamic (MHD) duct flow under the influence of highly varying electro-magnetic field is the counterpart in theory. This project aims at designing an ALIP for a 1500 MWe SFR based on numerical simulation and experiment. A 3D multi-physics coupled model is established for the ALIP modeling. The project consists of several tasks: 1) to reveal the MHD flow characteristic in the ALIP channel (especially in the Hartmann boundary layer) under varying working conditions, e.g. flow rates, alternating electro-magnetic fields with different strength and shifting velocity; 2) to understand the mechanisms of flow instability in a large rated flow rate ALIP via a RANS-based MHD numerical model and by studying several influencing factors (e.g., the end-effect in the magnetic field of ALIP, small perturbations in magnetic or flow velocity fields, and the radial variations in magnetic field, eddy current and Lorentz force); 3) to suppress the flow instability by modifying the magnetic field distribution or the pump's geometrical structure. The findings of this project will bring out a deeper insight on the flow characteristic of the MHD duct flow in higher Re number and strongly varying magnetic field in the perspective of fundamental research. The project will also provide the theoretical and experimental implications in the design of large rated flow rate ALIPs.

ALIP电磁泵在大流量下内部流场稳定性控制是设计和制造第四代钠冷快堆核主泵最关键的问题，研究磁流体在强变化电磁场作用下流动稳定性是解决该问题的基础研究。本项目将以可冷却1500 MWe级钠冷快堆的ALIP作为设计目标，建立ALIP三维磁-流-热多场耦合数值模型，并开展相关实验验证。主要研究内容有：1）基于LES模拟探明磁流体在外加强交变电磁场作用下通道内流动特性，掌握在不同流量、不同电磁场强度和迁移速度下通道内（特别是在哈特曼边界层中）流态特性。2）采用基于RANS方法的MHD模型探究ALIP在大流量下内部产生不稳定现象的机理，包括泵两端产生的非对称磁场对磁流体的作用，泵内沿径向分布磁场、涡电流对泵内磁流体流动的影响等。3）从改变磁场分布和泵内结构的角度，提出主动控制方案。本项目成果将提高对磁流体管道流在高雷诺数和强变化磁场下的认识；在应用研究上将为设计大流量核主泵提供理论和实验支撑。

本项目以第四代钠冷快堆核主泵可能采用的ALIP电磁泵为研究对象，针对其在大型化设计中出现的内部非稳态流动为研究内容，通过建立二维和三维数值模型来模拟泵内液态金属钠在交变电磁场耦合作用下瞬态流动过程，重点研究了泵内、外双侧布置线圈与传统单侧布线对速度、磁场、洛伦兹力产生的影响；三维泵内流道瞬态流动过程及非稳态流动（涡流、回流）产生的机理和时空演化特性，发现了双侧布线可以显著均化泵内流道各物理场沿径向分布、泵内非稳态流动产生的临界流量、泵内子午面涡流先从外侧产生逐渐扩大、泵内周向面涡流的区域和大小与脉动速度和磁场的波长有关，在此基础上提出了两种泵内稳流设计方案。目前国际上日本、韩国、俄国和法国针对此类泵都有大量研究，其中日本更是成功研制了一款流量超100方的示范泵。本项目的研究成功填补了我国在这方面的研究空白，为设计大型ALIP电磁泵提供了理论模型和设计模拟方法，具有较重要的应用价值。