长脉冲等离子体放电下HT-7装置限制器温度变化及能流分析

 在HT-7托卡马克等离子体长脉冲放电过程中，作为直接面对等离子体的第一壁限制器表面的温度变化及其承受的能流密度的计算，对于判断限制器的作用和对等离子体的影响都有非常重要的意义。主要从测量到的距离限制器表面3mm处温度变化曲线,采用无限大平面模型计算限制器模头表面能量沉积的能流密度,并讨论了不同等离子体放电下局部点能流密度的差别。多数长脉冲放电下，少数局部点的温升超过1 000℃，最大能流密度超过10MW/m ²；但通过对等离子体位移的控制，局部点温升被抑制，高密度能流持续时间短，有利于长脉冲放电。同时对限制器结构和材料对模头温度的影响也做了比较详细的分析。     

Numerical solution of compressible flow in a channel and blade cascade

This paper deals with a numerical solution of compressible flows. In the case of Euler equations, a numerical solver is presented on a structured quadrilateral grid. The Advection Upstream Splitting Method (AUSM) scheme is used and the spatial accuracy is improved by linear reconstruction with slope limiters. The influence of those limiters are then tested in cases of transonic flow through a channel and a blade cascade.     

HL-2M 装置限制器系统设计及工艺研究

HL-2M 装置设计有 8 套固定极向限制器和 1 套活动极向限制器,其主要功能是进一步加强保护真空 室及其内部件,同时活动限制器还将提供不同孔栏位形用于等离子体物理实验。根据 HL-2M 装置总体运行需求, 活动限制器结构设计可移动有效距离为 120mm,活动限制器移动精度可控制在±0.1mm 以内。基于激光跟踪仪测 量方法对 HL-2M 装置限制器系统完成了高精度的安装,限制器的面向等离子体关键位置安装精度优于±0.5mm, 通过初始等离子体放电实验表明其运行状态均正常。      

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对流动的液态锂限制器回路平台的热力学及流动性进行了分析.通过ANSYS分析发现,限制器工作在350℃的温度下,通过真空室壁内侧添加的热屏蔽层及氦冷的应用,可以有效地控制真空室壁的温度在180℃以下.对注锂管法兰的温度分析发现,通过流速2.5m.s-1的水冷设计,能够控制法兰刀口位置的温度在60℃左右.根据液态锂2m3.h-1的流量设计要求,分别估算了液态锂回路中沿程阻力损失及局部阻力损失,综合回路中的锂流动盘与电磁泵之间的高度压差,计算出液态锂驱动所需的电磁泵压头为14.2m.根据流动液态锂实验回路的热力学及流动性分析,设计完成了液态锂回路并开展了流动液态锂实验.实验结果表明,系统温度控制合适,没有出现真空室或注锂法兰过热引起的泄漏.同时电磁泵能够克服阀门及管道的阻力等顺利的驱动液态锂流动形成闭合的循环回路.     

基于PLC 驱动的步进电机的HL-2A 装置孔栏位移控制系统的设计与实现

为了实现HL-2A 装置孔栏位移自动控制,根据步进电机的应用原理,设计了孔栏位移自动控制系统。选用两相混合式步进电机,采用S7- 300PLC 作为主控制器,FM453 作为步进电机的定位模块,实现了对孔栏步进电机的驱动、控制与检测。同时完成了与上位机的通信,实现了对HL-2A 装置孔栏位移设置和数据显示等功能。     

NEW APPROACH TO THE LIMITER FUNCTIONS

1.IntroductionSince1980's,differenceschemeswithTVDorTVBpropertieshavebeenusedformoreandmoreCFDproblems,especiallythefollowingsystemofconservationlaws:ThereasonisthattheTVBpropertywillguaranteetheconvergenceofanysubsequenceofthedifferencesolutionsequencetoaweeksolutionofthedifferentialequation.Obviouslyiftheweeksolutionisunique,thenthewholesequencewillconvergetothatsolution.OneofthefrequentlyusedTVDschemeisthesecondorderfive--pointconservativeone:HereHi 1/2~H(Ull,,Uln,Uz71,U17,),iscons…     

Accuracy preserving limiter for the high-order accurate solution of the Euler equations

Higher-order finite-volume methods have been shown to be more efficient than second-order methods. However, no consensus has been reached on how to eliminate the oscillations caused by solution discontinuities. Essentially non-oscillatory (ENO) schemes provide a solution but are computationally expensive to implement and may not converge well for steady-state problems. This work studies the extension of limiters used for second-order methods to the higher-order case. Requirements for accuracy and efficient convergence are discussed. A new limiting procedure is proposed. Ringleb’s flow problem is used to demonstrate that nearly nominal orders of accuracy for schemes up to fourth-order can be achieved in smooth regions using the new limiter. Results for the fourth-order accurate solution of transonic flow demonstrates good convergence properties and significant qualitative improvement of the solution relative the second-order method. The new limiter can also be successfully applied to reduce the dissipation of second-order schemes with minimal sacrifices in convergence properties relative to existing approaches.     

HL－1真空室的运行状态分析

ＨＬ－１托卡马克从１９８４年建成至１９９２年底共运行了８年，获得了丰硕的物理实验和工程技术的科研成果，真空室运行状态总的来说是良好的。本文描述真空室在高功率放电实验运行了８年后的主密封结构状态、孔栏烧蚀、真空室壁状态及其污染概况等。     

A Parameter-Free Generalized Moment Limiter for High-Order Methods on Unstructured Grids

A parameter-free limiting technique is developed for high-order unstruc- tured-grid methods to capture discontinuities when solving hyperbolic conservation laws. The technique is based on a "troubled-cell" approach, in which cells requiring limiting are first marked, and then a limiter is applied to these marked cells. A parameter-free accuracy-preserving TVD marker based on the cell-averaged solutions and solution derivatives in a local stencil is compared to several other markers in the literature in identifying "troubled cells". This marker is shown to be reliable and efficient to consistently mark the discontinuities. Then a compact high-order hierarchical moment limiter is developed for arbitrary unstructured grids. The limiter preserves a degree $p$ polynomial on an arbitrary mesh. As a result, the solution accuracy near smooth local extrema is preserved. Numerical results for the high-order spectral difference methods are provided to illustrate the accuracy, effectiveness, and robustness of the present limiting technique.     

A Comparison of the Performance of Limiters for Runge-Kutta Discontinuous Galerkin Methods

Discontinuities usually appear in solutions of nonlinear conservation laws even though the initial condition is smooth, which leads to great difficulty in computing these solutions numerically. The Runge-Kutta discontinuous Galerkin (RKDG) methods are efficient methods for solving nonlinear conservation laws, which are high-order accurate and highly parallelizable, and can be easily used to handle complicated geometries and boundary conditions. An important component of RKDG methods for solving nonlinear conservation laws with strong discontinuities in the solution is a nonlinear limiter, which is applied to detect discontinuities and control spurious oscillations near such discontinuities. Many such limiters have been used in the literature on RKDG methods. A limiter contains two parts, first to identify the "troubled cells", namely, those cells which might need the limiting procedure, then to replace the solution polynomials in those troubled cells by reconstructed polynomials which maintain the original cell averages (conservation). [SIAM J. Sci. Comput., 26 (2005), pp. 995-1013] focused on discussing the first part of limiters. In this paper, focused on the second part, we will systematically investigate and compare a few different reconstruction strategies with an objective of obtaining the most efficient and reliable reconstruction strategy. This work can help with the choosing of right limiters so one can resolve sharper discontinuities, get better numerical solutions and save the computational cost.