流出圆形分支管道引起的MHD效应实验研究(英文)

介绍了在液态金属实验回路上开展的流体从分支管道流出引起的三维(3D)磁流体动力学(MHD)效应研究所取得的结果。包括两种情况下的流速分布和三维 MHD 压降效应,即磁流体流出分支管道阀门关闭和开启状态下实验值和理论值的比较,通过理论分析得出三维 MHD 压降效应的修正因子。     

流体从分支管道流人引起的3维磁流体动力学效应

分支管道引起的磁流体动力学(MHD)效应是磁约束聚变堆液体金属包层或自冷包层的关键问题之一。然而,由于磁流体的复杂性和实验条件的限制,尤其2维(2D)和3维(3D)效应的实验数据还很少,分支管道的MHD效应实验结果尚未见报道,而且MHD压降理论值与实验值相差10％～25％,何种原因尚未深究。继开展流出分支管道引起的磁流体动力学     

液态金属实验回路(LMEL)的总体设计和运行

液态金属实验回路（ＬＭＥＬ）是国内唯一用于聚变堆磁流体动力学（ＭＨＤ）效应和材料相容性研究的大型实验装置。与国外同类先进的装置相比，回路流程和运行方式均有重大改进，使其更先进、安全并具有多功能。回路运行分为两个阶段：第一阶段以钠－钾低共熔合金（２２Ｎａ７８Ｋ）为工质，研究ＭＨＤ效应，ＬＭＥＬ的最大哈特曼（Ｈａｒｔｍａｎｎ）数Ｍ和相互作用参数Ｎ分别为０．７５×１０４和２．５×１０４；第二阶段以液态锂为工质，研究结构材料与锂的相容性，最高温度和流速分别为５２０℃和１．３８ｍ／ｓ。     

流出分支管道引起的3维MHD效应研究

目前,磁流体动力学2维(2D)和3维(3D)效应的实验数据还很少,分支管道的MHD效应实验结果尚未见报道,圆形管道的流速分布尚没有完整的实验数据。我们利用国际合作渠道提供的仪器和国内液态金属回路的特点开展的3D磁流体动力学效应实验研究。实验在我国专门研究磁流体的动力学效应的液态金属回路上进行。其参数为:最大磁场强度2 T,最大哈德曼数M为4000,最大相互作用参数N为3600(聚变堆中M,N均在10~3～10~5范围内),回路工作介质为低共融钠钾合金,运行温度85℃,实验段管道由304不锈钢制成,主管道内径φ_0为57mm,壁厚t_(w0)为3.5mm;支管内径φ_1为22mm,壁厚t_(w1)为3.0mm;约24％流量流入支管;     

二维流速分布引起的MHD压降效应(英文)

磁流体动力学流体在管道截面上的流速分布关系到材料的相容性、传热以及磁流体动力学(MHD)压降。为此研究了矩形管道截面中心线上的流速分布和由于二维流速分布引起的MHD压降效应。在这一领域,首次得出的二维效应因子,解释了目前的理论值为什么比实验值低的原因。     

压水堆管道小破口蒸汽临界流泄漏实验研究

为探究压水堆核电厂小破口失水事故中管道小破口蒸汽临界流泄漏特性,开展了管道小破口泄漏实验,以探索饱和/过热蒸汽临界流泄漏特性。基于压力管道疲劳贯穿裂纹（微通道）,开展了流体压力3～12 MPa、流体温度240℃～320℃范围内的蒸汽临界流泄漏实验。实验结果表明,蒸汽临界质量流速与初始流体压力呈正相关关系,与初始流体过热度呈负相关关系。与过冷水临界流泄漏相比,蒸汽临界质量流速受入口压力损失、摩擦效应与加速效应的影响相对较弱。利用一维等熵模型预测了蒸汽临界质量流速,预测值与实验值平均相对偏差为14.17%,表明一维等熵模型具有良好的蒸汽临界质量流速预测精度。     

液态金属锂回路的总体设计及安装调试

液态金属锂回路是用来研究聚变堆中ＭＨＤ压降及材料相容性等工程问题的大型装置。本文主要介绍了建在核工业酉南物理研究院的锂回路装置设计参数，回路结构及组成部分和回路的主要技术指标。此回路由液态金属流动区域的主回路及氩气系统、真空系统、油冷系统、供电及控制系统、数据采集及处理系统、安全及报警系统等组成。此回路运行分两个阶段：第一阶段采用Ｎａ－Ｋ合金于常温下运行来研究ＭＨＤ压降，第二阶段采用金属锂于３５０～５００℃下运行来研究材料相容性。代表回路特性的Ｈａｒｔｍａｍ参数及相互作用参数分别为６３４３，１２１７２，液态金属在管道中最大流速达１．３８ｍ／ｓ，磁场强度达２．０Ｔ。     

托卡马克的实验结果

本文从ＭＨＤ不性、等离子体中快粒子、电流分布、面对等离子体的材料、等离子体加热和电流驱动、热和粒子排出及等离子体约束等方面，扼要介绍了托卡马克的主要实验结果。     

基于修正AIAD模型的稳压器波动管CCFL现象数值模拟

现阶段采用的第三代核电技术广泛引入非能动自动卸压系统,提高了反应堆的安全性,但是破口事故后可能引发的气液相向流动限制现象(Counter-Current Flow Limitation,CCFL)会增加稳压器波动管自身的安全风险,因此对稳压器波动管中CCFL现象的研究非常重要。本文采用自由表面模型结合修正的AIAD(Algebraic Interfacial Area Density)模型对稳压器波动管CCFL现象进行了三维数值模拟。通过与之对应的实验现象比较,结果分析表明:所使用的模型可以正确模拟该现象下汽液两相的相间作用;并通过对气相流速和倾斜角的敏感性分析,可以得到如下结论:阻塞的推进主要受初始气相流速和稳压器波动管倾斜角的影响,在靠近管道起始点的位置主要受初始气相流速影响,远离管道起始点的位置主要受倾斜角的影响。     

TCB混合堆Li自冷包层MHD流动设计

从磁流体动力学ＭＨＤ压降的物理原理出发，对ＴＣＢ商用混合堆Ｌｉ自冷包层的ＭＨＤ流动方式进行了改进，提出了第一壁环向流动（平行环向磁场流动），核燃料增殖区径向流动的ＭＨＤ流动的设计，以解决混合堆为改善堆的经济性而采取提高包层核燃料富集度的途径所速来的热工，ＭＨＤ压降和安全问题。分析和数值计算结果表明，第一壁环向流动设计可以满足包层核燃料富集度从０．５％增加到１％，相应的热功率从４５００ＭＷ增加到...     

Effect of electromagnetic coupling on MHD flow in the manifold of fusion liquid metal blanket

In fusion liquid metal (LM) blanket, magnetohydrodynamics (MHD) effects will dominate the flow patterns and the heat transfer characteristics of the liquid metal flow. Manifold is a key component in LM blanket in charge of distributing or collecting the liquid metal coolant. In this region, the complex three dimensional MHD phenomena will be occurred, and the velocity, pressure and flow rate distributions may be dramatically influenced. One important aspect is the electromagnetic coupling effect resulting from an exchange of electric currents between two neighboring fluid domains that can lead to modifications of flow distribution and pressure drop compared to that in electrical separated channels. Understanding the electromagnetic coupling effect in manifold is necessary to optimize the liquid metal blanket design.In this work, a numerical study was carried out to investigate the effect of electromagnetic coupling on MHD flow in a manifold region. The typical manifold geometry in LM blanket was considered, a rectangular supply duct entering a rectangular expansion area, finally feeding into 3 rectangular parallel channels. This paper investigated the effect of electromagnetic coupling on MHD flow in a manifold region. Different electromagnetic coupling modes with different combinations of electrical conductivity of walls were studied numerically. The flow distribution and pressure drop of these modes have been evaluated.     

Code validation for the magnetohydrodynamic flow at high Hartmann Number based on unstructured grid

In order to analyze the magnetohydrodynamic (MHD) effect in liquid metal fusion blanket, a parallel and high performance numerical code was developed to study MHD flows at high Hartmann Number based on the unstructured grid. In this code, the induced current and the Lorentz force were calculated with a current density conservative scheme, while the incompressible Navier–Stokes equations with the Lorentz force included as a source term was solved by projection method, a set of method were used to improve the computing performance such as Krylov subspace method and AMG method. To validate this code, three benchmarks of MHD flow at high Hartmann Number were conducted. The first benchmark was the case of Shercliff fully development flow, the second benchmark was the MHD flow in a circular pipe with changing external magnetic field, and the third benchmark was the MHD flow in a pipe with sudden expansion. In these cases the Hartmann Numbers were from 1000 to 6000. The code good computing performance, and numerical results show matched well with the analytical and experimental results.     

Analysis on MHD Stability of Free Surface Jet flow in a Gradient Magnetic Fields

The simplified modeling for analysis on MHD stability of free surface jet flow in a gradient magnetic fields is based on the theoretical and experimental results on channel liquid metal MHD flow, especially, the results of MHD flow velocity distribution in cross-section of channels (rectangular duct and circular pipe), and the expected results from the modeling are well agreed with the recent experimental data obtained. It is the first modeling which can efficiently explain the experimental results of liquid-metal free surface jet flow.     

Liquid metal magnetohydrodynamic flows in manifolds of dual coolant lead lithium blankets

An attractive blanket concept for a fusion reactor is the dual coolant lead lithium (DCLL) blanket where reduced activation steel is used as structural material and a lead lithium alloy serves both to produce tritium and to remove the heat in the breeder zone. Helium is employed to cool the first wall and the blanket structure.Some critical issues for the feasibility of this blanket concept are related to complex induced electric currents and 3D magnetohydrodynamic (MHD) phenomena that occur in distributing and collecting liquid metal manifolds. They can result in large pressure drop and undesirable flow imbalance in parallel poloidal ducts forming blanket modules.In the present paper liquid metal MHD flows are studied for different design options of a DCLL blanket manifold with the aim of identifying possible sources of flow imbalance and to predict velocity and pressure distributions.     

Influence of Transverse Magnetic Field on Heat Transport Characteristics of Potassium Heat Pipe

The influence of a transverse magnetic field on the heat transport characteristics of a potassium heat pipe was experimentally studied in the range of field strength 0~0.6 T. The wick was constituted of a multilayer mesh screen, and the adiabatic section, to which the magnetic field was applied, was made up of a concentric double-wall rectangular tube, with the inner wall completely separating the vapor and liquid flows.

The magnetic field was applied perpendicularly to the heat pipe, upon which the axial temperature distribution of the heat pipe was observed to be affected, and the heat transport rate to be reduced with increasing field strength.

The effect of the magnetic field on the heat transport rate is analyzed in terms of the liquid pumping ability of the wick and of the magnetohydrodynamic (MHD) effect on the liquid flow through the wick. The MHD effect on the flow through wick is shown to be expressible by a formula similar to that for flow between parallel plates.

The heat transport rate measured in magnetic field are compared with values calculated assuming that the wick pumping ability was not influenced by the magnetic field but that it was the MHD effect on the liquid flow through the wick that affected the heat transport. The calculated results well explained the experimental data.     

Experimental and numerical studies of pressure drop in PbLi flows in a circular duct under non-uniform transverse magnetic field

Experiments and three-dimensional (3D) numerical simulations are performed to investigate the magnetohydrodynamic (MHD) characteristics of liquid metal (LM) flows of molten lead-lithium (PbLi) eutectic alloy in an electrically conducting circular duct subjected to a transverse non-uniform (fringing) magnetic field. An indirect measurement approach for differential pressure in high temperature LM PbLi is first developed, and then detailed data on pressure drop in this PbLi MHD flow are measured. The obtained experimental results for the pressure distribution are in good agreement with numerical simulations. Using the numerical simulation results, the 3D effects caused by fringing magnetic field on the LM flow are illustrated via distributions for the axial pressure gradients and transverse pressure differences. It has been verified that a simple approach for estimation of pressure drop in LM MHD flow in a fringing magnetic field proposed by Miyazaki et al. [22] i.e., a simple integral of pressure gradient along the fringing field zone using a quasi-fully-developed flow assumption, is also applicable to the conditions of the present experiment providing the magnetic interaction parameter is large enough. Furthermore, for two different sections of the LM flow at the entry to and at the exit from the magnet, it is found that the pressure distributions in the duct cross sections in these two regions are different.     

Development of a three-dimensional magnetohydrodynamics code for electromagnetic pumps

Annular linear induction pumps (ALIPs) are one of the electromagnetic (EM) pumps, which drive liquid metal using EM force, for fast reactors and have been developed in many countries. An ALIP mainly consists of multiple coils, iron cores and an annular flow channel. We have calculated the developed pressure of ALIPs using a two-dimensional magnetohydrodynamics (MHD) code. There are some reports in which pressure drop and fluctuation were observed in EM pump operations near the top of the pressure and flow rate relation (P–Q) curve. For fear of this phenomenon, the EM pump design is sometimes too conservative. To simulate the pressure drop and fluctuation occurrence conditions, we have developed a new three-dimensional (3D) MHD code. Clarification of this condition and its phenomena in the sodium flow will enable design of a new structure or determination of operation conditions that preclude this pressure drop and fluctuation and, thereby, achieve high efficiency. In this paper, the model of our new 3D MHD code, the accuracy of the code, simulation results focusing on pressure drop and fluctuation by radial and circumferential vortices are reported.     

Three-Dimensional Numerical Calculations on Liquid-Metal Magneto-hydrodynamic Flow through Circular Pipe in Magnetic-Field Inlet-Region

Three-dimensional numerical calculations have been performed on liquid-metal magnetohydrodynamic (MHD) flows through a circular pipe in the inlet region of the applied magnetic field, including a sufficient calculation region upstream in the magnetic field section. The continuity equation, the momentum equation including the Lorentz force term, and the induction equation derived from basic equations in the electromagnetism have been solved numerically. Along the flow axis (i.e., the channel axis), the pressure decreases slightly as a normal non-MHD flow, increases once, thereafter, decreases sharply, and finally decreases as a fully-developed MHD flow. The sharp decrease in the pressure, resulting in a large pressure drop in the inlet region is due to the increase in the induced electric current in this region compared with that in the fully-developed region. The velocity distribution changes from a parabolic profile of a laminar non-MHD flow to a profile with peaks near the walls parallel to the magnetic field, and finally to a flat profile of a fully-developed MHD flow.     

MHD Stability Analysis and Flow Controls of Liquid Metal Free Surface Film Flows as Fusion Reactor PFCs

Numerical and experimental investigation results on the magnetohydrodynamics(MHD) film flows along flat and curved bottom surfaces are summarized in this study. A simplified modeling has been developed to study the liquid metal MHD film state, which has been validated by the existing experimental results. Numerical results on how the inlet velocity(V), the chute width(W) and the inlet film thickness(d0) affect the MHD film flow state are obtained. MHD stability analysis results are also provided in this study. The results show that strong magnetic fields make the stable V decrease several times compared to the case with no magnetic field,especially small radial magnetic fields(Bn) will have a significant impact on the MHD film flow state. Based on the above numerical and MHD stability analysis results flow control methods are proposed for flat and curved MHD film flows. For curved film flow we firstly proposed a new multi-layers MHD film flow system with a solid metal mesh to get the stable MHD film flows along the curved bottom surface. Experiments on flat and curved MHD film flows are also carried out and some firstly observed results are achieved.     

Numerical study of the MHD flow characteristics in a three-surface-multi-layered channel with different inlet conditions

A 3D MHD flow simulation was conducted to clarify the effects of the inlet flow conditions on the results of the validation experiment carried out previously and on the design window of the first wall using a three-surface-multi-layered channel. MHD pressure drop was largely influenced by the inlet condition. The numerical model with turbulent velocity profile showed qualitatively good agreement with the experimental result. The first wall temperature and pressure distributions obtained by the 3D simulation corresponded well to those obtained by the 2D simulation assuming fully developed flow. This suggested that complicated three-dimensional inlet flow condition generated in the L-shape elbow would not affects the existing design window.