Numerical Simulation of Non-Inductive Current Driven Scenario in EAST Using Neutral Beam Injection

For achieving the scientific mission of long pulse and high performance operation,experimental advanced superconducting tokamak(EAST) applies fully superconducting magnet technology and is equiped with high power auxiliary heating system.Besides RF(Radio Frequency) wave heating,neutral beam injection(NBI) is an effective heating and current drive method in fusion research.NBCD(Neutral Beam Current Drive) as a viable non-inductive current drive source plays an important role in quasi-steady state operating scenario for tokamak.The non-inductive current driven scenario in EAST only by NBI is predicted using the TSC/NUBEAM code.At the condition of low plasma current and moderate plasma density,neutral beam injection heats the plasma effectively and NBCD plus bootstrap current accounts for a large proportion among the total plasma current for the flattop time.     

采用无网格移动粒子法数值模拟闪蒸射流

采用具有良好捕捉流体界面特性的无网格移动粒子法(MPS粒子法)对闪蒸射流过程进行二维直接数值模拟。该数值方法采用完全的拉格朗日描述定义流体运动，流体离散为可移动的粒子，流体控制微分方程转化为粒子间的相互作用。直接数值模拟结果与相关实验结果一致：发生于界面的闪蒸将射流剥落为锥状，射流长度随压力衰减比的增加而变短。     

Numerical Simulation of Voltage Applied to the Gaps of a Planar Multi-Gap Multi-Channel Gas Switch

In the linear transformer driver (LTD) technology, the low inductance energy storage components and switches are directly incorporated into the individual cavities (named stages) to generate a fast output voltage pulse, which is added along a vacuum coaxial line like in an inductive voltage adder. To provide the theoretical foundation for structure design and ensure the reliable operation of the planar multi-gap multi-channel gas switches, numerical simulation of voltage applied to the gaps is carried out, taken into account a variety of factors such as working coefficient, triggering voltage, resistance of crosswise resistors, and coupling capacitance. Based on the theoretical analysis of development and maintenance of parallel discharge channels, simulation of voltage applied to the gaps was performed in PSpice program. The results of simulation show that high working coefficient, high triggering voltage, high resistance of crosswise resistors and high coupling capacitance are all beneficial to the increase of the voltage applied to the gaps.     

Numerical Simulation of Subcooled Boiling Inside High-Heat-Flux Component with Swirl Tube in Neutral Beam Injection System

In order to realize steady-state operation of the neutral beam injection（NBI） system with high beam energy,an accurate thermal analysis and a prediction about working conditions of heat-removal structures inside high-heat-flux（HHF） components in the system are key issues.In this paper,taking the HHF ion dump with swirl tubes in NBI system as an example,an accurate thermal dynamic simulation method based on computational fluid dynamics（CFD） and the finite volume method is presented to predict performance of the HHF component.In this simulation method,the Eulerian multiphase method together with some empirical corrections about the inter-phase transfer model and the wall heat flux partitioning model are considered to describe the subcooled boiling.The reliability of the proposed method is validated by an experimental example with subcooled boiling inside swirl tube.The proposed method provides an important tool for the refined thermal and flow dynamic analysis of HHF components,and can be extended to study the thermal design of other complex HHF engineering structures in a straightforward way.The simulation results also verify that the swirl tube is a promising heat removing structure for the HHF components of the NBI system.     

斜接管射流流动特性数值模拟

采用数值模拟方法对受限斜射流的流动特性、射流发展影响区域、射流发展关键因素及射流涡特性进行研究.研究表明:受限斜射流存在附壁斜射流、离升斜射流和冲击斜射流3种基本流型.流速比(V<,R>)是斜接管射流流动特性的关键特征参数;射流影响区域随V<,R>的增大而越大;在高V<,R>下,射流强烈冲击主管底面,并在上游形成明显回...     

采用低马赫数方法对空气射流破坏氦气分层现象的数值模拟

在对低速气体进行计算流体力学(CFD)数值模拟时,通常忽略气体的可压缩性。当计算体系中存在较大温差和较大组分浓度差时,不可压缩近似会因带来很大计算误差而失效。针对此问题,低马赫数方法通过将实际压力拆分为热力学压力和动力学压力的方式,将物性参数与热力学压力联系起来,在对不可压缩流动求解器进行较小改造后,较准确地处理低马赫数下的可压缩流问题。利用Code_Saturne程序实现该模型,并针对空气射流破坏轻密度气体分层现象进行模拟。首先通过网格敏感性分析,选定中等密度网格为计算网格;然后在比较不同算法的模拟结果中发现,采用低马赫数方法可以明显提高计算精度。最后,利用模拟结果,对空气射流破坏氦气分层实验中氦气的水平分布情况进行分析和讨论。     

斜接管嘴非等温横向射流时近壁流体温度的数值模拟

针对反应堆主管道45°安注斜接管嘴,基于1:9的比例模型,采用计算流体力学程序(CFX)软件,进行了常压条件下安注斜接管嘴主、射流温差分别为30℃和70℃、射流和主流的流速比为0.87～40、构件不同区域内非等温横向射流时的壁温变化及其分布特征的数值模拟研究,得出了构件内主接管相交区、射流下游区、主管侧面区及主管底部各区域测点近壁流体的混合函数。通过对射流与主管流体两种温差下各区域测点混合函数的比较发现,在本次研究中,30℃、70℃两种温差下各点混合函数基本保持不变,各点混合函数的大小与温差关系不大。将本文混合函数的计算结果与同期试验结果进行了比较,二者符合良好。     

UO_2核芯制备过程中分散滴球喷嘴内流动均匀性模拟研究

运用计算流体动力学(CFD)方法模拟了UO2核芯颗粒制备过程中分散滴球步骤涉及的喷嘴腔体内部流场,特别对每个喷头出口的流量通量均匀性进行分析研究。系统考察实际生产过程中可能影响喷头流量通量均匀性的4种可能性因素:入流方向、喷孔的分布位置、喷孔的水平度和喷孔的大小。从模拟结果中可以发现,喷孔的大小是相对最关键因素,是导致颗粒尺寸不均匀的主要原因之一,在实际生产制作中要尤其关注喷头孔径的加工尺寸。流动方程理论验证了上述模拟结果的正确性。     

冷坩埚玻璃固化启动过程数值分析

使用COMSOL有限元计算软件对熔池直径500 mm、高365 mm的电磁冷坩埚玻璃固化模型的启动过程进行了数值分析,研究了垂直方向环状启动加热块数量和位置分布对启动过程中加热速率、加热效率和温度分布的影响。计算结果表明,启动加热块距离坩埚底部250~300 mm时加热效率较高,增加垂直方向启动加热块的分布数量有利于在启动过程中加快升温速率、快速提高磁感应加热效率、加强玻璃熔体温度均匀程度和扩大玻璃熔体体积。     

稠密栅元内湍流流体的数值模拟

采用CFD软件Fluent对37棒束内的湍流流体进行了分析。利用实验数据对计算结果进行了验证,分析了棒 棒间隙的减小对稠密栅元内局部流动、传热和相干结构的影响。稠密栅元的临界P/D（棒间距/棒直径）约为1.03。随着P/D减小,相干结构和流体交混先增加然后迅速衰减。当通道间隙非常小时,相干结构运动非常弱以至于可将其忽略。其流速、壁面剪应力和壁面温度的波动也非常小,但其参数的空间分布的差异非常明显。     

离心机流场非稳态过程的初步数值模拟

摘要：从非稳态线性离心机流场运动方程出发，利用有限体积法，采用交错网格得到离散方程。通过数值求解得到了存在温度驱动情况下，离心机内形成小扰动流场的过程。从形成小扰动流场的非稳态过程可以看出扰动流场在开始和稳定阶段的影响因素不同，从温度引起的轴向压强的不平衡引起流动逐渐过渡到压强分布不同而引起的轴向环流。数值模拟为更好地研究离心机内流场的非稳态过程提供了依据。     

Numerical Simulation of Aerosol Behavior in Turbulent Natural Convection

This paper describes the detail numerical methods for the aerosol behavior in the cover gas regions of LMFRs by considering the aerosol growth as one of the space coordinates. The governing equations for the compressible gas were approximated by removing sound waves for the efficient calculations of the large temperature different fields. The convection terms of these equations were discretized by the 3rd order upwind scheme which was derived for irregular staggered mesh. In order to verify this method, a natural convection in the vertically heated enclosure was calculated and the results were compared with the benchmark results by de Vahl Davis. In this calculation, temperature distribution in the enclosure agreed well with each other. The basic heat transfer tests for the cover gas region of LMFRs were also calculated by this method and the calculated vertical average temperature profile of the turbulent cover gas natural convection and the aerosol average mass concentration were compared to the experimental ones. The calculated temperature agreed well with the experimental ones. It was also estimated that the aerosol were well mixed in the natural convection field and the number densities distributed the similar profiles in almost all region except for the region near the top surface.     

导管中冷中子传输过程的数值模拟

中子导管是利用中子全反射原理将中子束以很小的传输损失传递到远离中子源处的物理装置。利用蒙特卡罗方法模拟中子在导管中输运过程,在中子导管的设计和实验应用中可发挥重要作用。某座反应堆上正建设包括有3束导管的冷中子导管系统,以蒙特卡罗方法为基础,开发出该导管系统的数值模拟程序,并利用该程序计算得到该导管各个输出口的中子注量率及能谱分布,为布置在导管周围的中子散射谱仪和其它应用装置的设计提供了必要的输入条件。     

Numerical Simulation of Aerosol Behavior in Turbulent Natural Convection

In order to evaluate the aerosol behavior in detail in the cover gas region of LMFRs, a numerical method was developed by considering the aerosol radius as one of the space coordinates. In this method, the governing equations for the compressible gas were approximated by removing the sound wave in order to efficiently calculate the temperature field with a large gradient. The convection terms of these equations were discretized by the 3rd order upwind scheme which was derived for an irregular spaced staggered mesh system. Although it was shown in a previous study that this method was reasonable by calculating basic heat transfer tests of the cover gas region, it is desirable to improve the method in order to achieve more accurate results. In this study, advanced models were developed which simulate the interaction between the mixed gas and aerosols in the flow field. A comparison of the calculated results vs. the experimental results indicated good agreement of temperature distribution. In addition, the aerosol mass concentration in the cover gas region could be evaluated much better with this advanced model.     

窄间隙矩形多通道流动交混特性数值模拟

采用CFD程序CFX对窄间隙矩形多通道内流体的交混特性进行了数值模拟.数值计算结果表明:流体经过全部的交混段后,两边侧边通道内的流量低,中间4个主通道内的流最高.入口流量大小不同的条件下,流体经过全部的交混段后,主通道内的流量都趋于一致.前4段的流动交混较为明显,随着轴向交混段的增加,交混量越来越小;流体交混时,主通道入口流量大的通道内的流体向入口流量小的通道内运动,初始阶段在侧边通道和交混段产生了较强的二次流,但随着轴向交混段的增加,二次流变得越来越小.     

涡流式分离器气液两相分离数值模拟研究

对于气液两相分离,传统分离器或体积过大,或旋流强度低,因此考虑提出一种新式的涡流式分离器。利用涡流二极管逆向流动形成强度较高旋流的特点,在旋流腔上方加入一根支管,从切向入口进入的两相流由于密度差和旋流的作用,气相会聚集在中心由于浮力作用从上支管流出分离器,液相会分布在四周由于重力作用从下支管流出分离器,从而实现两相分离。采用数值模拟的方式分别对不同旋流腔尺寸以及出口形状的分离器进行计算,模拟结果表明,在进口流量为0.5 t/h、入口含气率1%～5%工况下,控制底流口压力和入口相同,溢流口与入口压差在80～90 kPa范围内,分离器对粒径在50～100μm的气泡分离效率可以达到90%以上。     

严重事故中碎片床形成过程的数值模拟

采用改进的离散要素法(DEM)对严重事故中碎片床的形成过程进行二维数值模拟。针对传统的DEM模型中计算系数选取困难的问题,围绕时间步长对计算参数重新进行推导和组合,改进后的DEM能大大提高应用的效率。通过与一系列的实验在颗粒扩散角度、颗粒下落时间、形成碎片床的形状方面的系统对比,验证了模拟程序的有效性。     

多孔介质通道中单相流阻力特性数值模拟

以流体分析软件Fluent6.3为平台,建立了颗粒填充多孔介质通道内单相流体的流动阻力预测模型。结果表明:该预测模型具有较高的计算精度,对于无量纲直径D=0.16、0.1和0.04的多孔介质通道,预测值与实验值间的相对偏差分别小于5%、7%和7%;流动阻力随D的增大而减小;对于多孔介质中单相流体的压降,现有模型中的惯性阻力修正系数CF对计算结果的影响显著,不能对阻力压降进行很好地预测。     

换热器传热管与支承板碰撞力的数值模拟

在流动诱发振动的作用下,传热管的微振磨损,是导致换热器损坏的重要原因之一.预测管子微振磨损率的一个关键参数是管子-支承碰撞力.本文利用有限元模型计算了单跨悬臂管作平面运动时的管子-支承振动碰撞力.数值模拟的结果与实验数据作了比较,实验数据与分析的结果是相符的.