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Numerical simulation of tetrahedral particle mixing and motion in rotating drums

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Particuology 2018年第4期16卷 1-11页

作者： Nan Gui xingtuan yang Jiyuan Tu Shengyao Jiang Institute of Nuclear and New Energy Technology Collaborative Innovation Center of Aclvanced Nuclear Energy Technology Key Laboratory of Advancecl Reactor Engineering and Safety of Ministry of Education Tsinghua University Beijing 100084 China School of Engineering RMIT University Melbourne VIC 3083 Australia

A regular tetrahedron is the simplest three-dimensional structure and has the largest non-sphericity. Mixing of tetrahedral particles in a thin drum mixer was studied by the soft-sphere-imbedded pseudo- hard particle model and compared with that of spherical particles. The two particle types were simulated with different rotation speeds and drum filling levels. The Lacey mixing index and Shannon information entropy were used to explore the effects of sphericity on the mixing and motion of particles. Moreover, the probability density functions and mean values and variances of motion velocities, including translational and rotational, were computed to quantify the differences between the motion features of tetrahedra and spheres. We found that the flow regime depended on the particle shape in addition to the rotation speed and filling level of the drum. The mixing of tetrahedral particles was better than that of spherical particles in the rolling and cascading regimes at a high filling level, whereas it may be poorer when the filling level was low. The Shannon information entropy is better than the Lacey mixing index to evaluate mixing because it can reflect the real change of flow regime from the cataracting to the centrifugal regime, whereas the mixing index cannot.

关键词： Tetrahedron Non-spherical particle Mixing Drum Flow regime Discrete element method

Calculation of natural circulation under heaving motion

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Science China(Technological Sciences) 2014年第8期57卷 1658-1669页

作者： FENG BeiBei yang xingtuan JIANG ShengYao Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education Institute of Nuclear and New Energy TechnologyTsinghua University

Wide validation of self-developed program of natural circulation under oceanic conditions has been conducted compared with experimental data of inclination,zero-power condition and hot-state *** were performed on a full-scale,whole parameterization natural circulation loop designed with reference to 5 MW experimental low temperature nuclear heating reactor(NHR)of Tsinghua *** of natural circulation and parameter effect under heaving motion was carried out using the program and comparison of heaving,inclination and rolling on natural circulation respectively to reveal the influence *** indicate that:(1)significant influence of heaving motion on natural circulation was observed,and heaving motion with high level of strength and long cycle would lead to severe flow fluctuation;(2)slight effect was caused by short cycle heaving motion which was completely different from long cycle heaving motion;(3)comprehensive action of alternating force and flow density distribution would result in natural circulation under heaving motion;(4)most severe accidents maybe result from the long cycle heaving motion rather than inclination and rolling *** of influence of heaving motion on natural circulation could have important reference significance in the optimization design of nuclear reactors.

关键词： natural circulation oceanic condition NHR nuclear engineering

Effects of volumetric fraction and included angle of composite particles on the discharge of binary mixtures in hoppers

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Particuology 2020年第4期18卷 80-90页

作者： Liange Ge Nan Gui xingtuan yang Jiyuan Tu Shengyao Jiang Institute of Nuclear and New Energy Technology Collaborative Innovation Center of Advanced Nuclear Energy TechnologyKey Laboratory of Advanced Reactor Engineering and SafetyMinistry of EducationTsinghua UniversityBeijing 100084China School of Engineering RMIT UniversityMelbourneVIC 3083Australia

The discharge behavior of particles is important in many industrial applications,such as in the core of a pebble bed reactor,which uses a hopper bed filled with many large *** this work,a mixture composed of two particle types,freely discharged from a pebble bed,is simulated using the discreteelement *** is a spherical pebble of diameter equal to that of the fuel pebble of the *** other is a composite particle comprising three spherical pebbles bonded *** included angleαof the three pebbles characterized the particle conformation,which may affect the discharge behavior of the *** effects of volume fraction of the multi-sphere x(equivalent to the number fraction)on the discharge are also *** patterns,number flow rate,discharge velocity,and mean force of the mixture are computed to help in revealing discharge *** results show that increasing eitherαor x reduces the discharge flow *** and correlations give a quantitative evaluation of the independent effects ofαand *** analysis of velocity and force explains the mechanism relevant to the main influencing factorsαand *** results are helpful in gaining a better understanding of the discharge feature of binary mixtures and in providing a quantitative evaluation of the discharge behavior of the reactor core,especially adverse failure conditions.

关键词： Pebble flow Particle flow Discharge flow Hopper bed Binary mixture Discrete element method

NHR200-Ⅱ卧式蒸汽发生器的比例缩放试验设计

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核动力工程 2024年第5期45卷 136-141页

作者：李宗洋郝文涛张文文李卫华杨星团清华大学核能与新能源技术研究院北京100084

为拓宽200 MW低温核供热堆(NHR200-Ⅱ)的应用范围和提高其经济性,重新对其中间回路进行设计,并提出包含卧式蒸汽发生器(HSG)在内的新型过热蒸汽供应系统。因原型尺度的验证试验成本高、周期长,故采用多级双层比例分析(H2TS)方法对HSG内... 详细信息

为拓宽200 MW低温核供热堆(NHR200-Ⅱ)的应用范围和提高其经济性,重新对其中间回路进行设计,并提出包含卧式蒸汽发生器(HSG)在内的新型过热蒸汽供应系统。因原型尺度的验证试验成本高、周期长,故采用多级双层比例分析(H2TS)方法对HSG内的两相自然循环开展比例模化分析研究,并通过理论推导给出了在等物性条件下的比例分析准则和不同比例条件下的比例数值。原型和模型均选用水作为试验工质,再结合RELAP5程序对原型和模型进行仿真建模。仿真计算结果表明模型和原型的关键参数比例关系符合理论推导结果。综合考虑试验经济性、准确性、安全性等因素,最终确定模型和原型的长度比例为1∶4作为后续验证试验的长度比值,对应的功率比为1∶96。

关键词： 200 MW低温核供热堆(NHR200-Ⅱ) 卧式蒸汽发生器(HSG) 比例分析仿真

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Thermo-hydraulic experimental validation of an integrated modular small reactor operating in full power natural circulation

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Science China(Technological Sciences) 2014年第1期57卷 1-8页

作者： yang xingtuan REN Cheng LIU ZhiYong TU JiYuan JIANG ShengYao Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education Institute of Nuclear and New Energy Technology Tsinghua University

Small reactors have become a new hotspot of international nuclear energy *** nuclear heating reactor(NHR)technology developed by Tsinghua University is an important multipurpose small reactor solution with features such as high integration,modular design and full power natural circulation.A new small reactor based on the existing NHR-200 reactor was developed by the Institute of Nuclear and New Energy Technology of Tsinghua University.A full-scale natural circulation test loop with the same operating parameters as the actual reactor was built in order to experimentally validate the natural circulation ability of the reactor primary loop and heat-transfer ability of fuel assemblies and heat *** results are given in detail,including parameter validation of the reactor primary loop,flow rules of the natural circulation and heat-transfer coefficients of heaters and heat exchangers,which can be directly used in the actual reactor as a reference for optimization ***,a characteristic parameter k is proposed to represent the natural circulation ability of a *** using the new data arrangement method in the form of parameter k,comprehensive experimental results of the natural circulation can be represented by a simple integrated *** work in this paper is of importance in broadening application fields and pushing forward commercialization of the NHR type reactors.

关键词： small reactor natural circulation validation experiment

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不均匀加热与节流对平行通道不稳定性的影响

哈尔滨工业大学学报 2020年第1期52卷 28-35页

作者：白宇飞杨星团张震清华大学核能与新能源技术研究院北京100084 清华大学先进核能技术协同创新中心北京100084 先进反应堆工程与安全教育部重点实验室(清华大学) 北京100084

为研究反应堆内轴向热流不均匀分布、径向不均匀加热和入口节流对密度波不稳定的影响,利用RELAP5/MOD4.0程序对强迫循环平行通道系统进行数值模拟.由程序中的非平衡非均相模型和半隐式数值格式所得计算结果与实验数据符合较好.对比轴向... 详细信息

为研究反应堆内轴向热流不均匀分布、径向不均匀加热和入口节流对密度波不稳定的影响,利用RELAP5/MOD4.0程序对强迫循环平行通道系统进行数值模拟.由程序中的非平衡非均相模型和半隐式数值格式所得计算结果与实验数据符合较好.对比轴向热流线性分布及余弦分布工况下的流动不稳定边界,并做出积分热流沿通道长度的变化曲线以分析其机理,还获取了径向不均匀加热与入口节流工况下系统和通道的临界相变数.结果表明:轴向热流不均匀分布时系统的稳定性取决于沸腾边界的位置以及积分热流沿通道的分布.与轴向热流均匀分布相比,轴向热流线性增大或减小分别使系统稳定性增强或减弱;入口过冷度较低时,轴向热流余弦分布提高系统稳定性;入口过冷度较高时,系统稳定性可能增强也可能减弱.与轴向热流余弦分布相比,峰值偏向入口或出口分别会降低或提高系统稳定性.径向不均匀加热对系统稳定性影响较小.增大径向入口节流不均匀性时系统稳定性有减小的趋势,增大任一通道入口节流系数均可提高系统的稳定性.

关键词：平行通道流动不稳定性不均匀加热不均匀节流 RELAP5

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起伏强度和周期对自然循环流动特性的影响

哈尔滨工程大学学报 2015年第4期36卷 448-451页

作者：封贝贝杨星团姜胜耀清华大学核能与新能源技术研究院先进反应堆工程与安全教育部重点实验室北京100084

为了研究起伏运动对自然循环流动特性的影响,针对以5 MW低温核供热堆(NHR)为基础建立的自然循环试验回路,自行开发计算程序研究起伏强度和周期对自然循环流动波动、加热段出口过冷度以及换热器二次侧出口过冷度的影响。建立数学模型,坐... 详细信息

为了研究起伏运动对自然循环流动特性的影响,针对以5 MW低温核供热堆(NHR)为基础建立的自然循环试验回路,自行开发计算程序研究起伏强度和周期对自然循环流动波动、加热段出口过冷度以及换热器二次侧出口过冷度的影响。建立数学模型,坐标系固定于试验本体上,采用流体相对速度,将起伏条件下自然循环问题转化为非惯性参考系问题,考虑起伏运动引入附加力对自然循环的影响,在重力g的前面乘一个随时间变化的系数(1-k·sin(ωdt))。计算结果表明:起伏强度k越大,流量和温度波动越大;起伏周期T越大,流量波动越大且呈现出明显的非线性波动,大周期的起伏运动可能造成加热段出口出现饱和甚至沸腾的情况。对起伏运动影响自然循环机理的分析表明:起伏引入的附加作用力和重力一起构成一个交变力场,在有密度差的情况下形成自然循环驱动力,从而引起自然循环流动。

关键词：起伏运动起伏强度周期自然循环过冷度流量波动影响机理

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粒子法中压力振荡的机理研究

力学学报 2018年第3期50卷 688-698页

作者：朱跃姜胜耀杨星团段日强清华大学核能与新能源技术研究院先进核能技术协同创新中心教育部先进反应堆工程与安全重点实验室北京100084

移动粒子半隐式法(moving particle semi-implicit method,MPS)是一种适用于不可压缩流体的无网格方法,MPS方法常应用于自由表面大变形问题.MPS方法提出至今一直存在着严重的压力振荡问题.本研究针对MPS方法中存在的压力振荡现象,首先... 详细信息

移动粒子半隐式法(moving particle semi-implicit method,MPS)是一种适用于不可压缩流体的无网格方法,MPS方法常应用于自由表面大变形问题.MPS方法提出至今一直存在着严重的压力振荡问题.本研究针对MPS方法中存在的压力振荡现象,首先将实际的物理问题简化为一维模型,并从粒子之间相互位置关系的角度说明了MPS方法中压力波动产生的原因.在采用MPS方法进行模拟时,加入了粒子碰撞模型,通过对碰撞系数的选择从而控制粒子之间的相互位置关系.并且对经典的溃坝问题进行了模拟,结果表明随着碰撞系数的增加,粒子数密度偏差的波动幅度都会减小,从而压力振荡的幅度得到了有效的抑制.并且对比了两种不同核函数对压力振荡的影响,结果表明:采用高斯核函数时,压力振荡的幅度更小,这是因为采用高斯核函数时,相同的粒子位置波动幅度将会得到较小的粒子数密度偏差的波动.由于在模拟过程中粒子运动的随机性,这将导致粒子数密度偏差产生随机的波动,从而产生压力振荡,因此粒子法中的压力振荡很难彻底消除.

关键词：移动粒子半隐式法压力振荡机理碰撞模型核函数

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自然循环中冷凝液滴自由表面识别的改进

原子能科学技术 2018年第9期52卷 1590-1597页

作者：朱跃姜胜耀杨星团段日强清华大学核能与新能源技术研究院先进核能技术协同创新中心先进反应堆工程与安全教育部重点实验室北京100084

自然循环过冷沸腾过程是第3代核电站非能动安全性的基础,该过程中冷凝液滴的传热计算对核电站的安全性具有重要意义。本研究采用移动粒子半隐式(MPS)方法对该过程进行模拟。为了对该过程中冷凝液滴传热传质界面的识别进行改进和优化,提... 详细信息

自然循环过冷沸腾过程是第3代核电站非能动安全性的基础,该过程中冷凝液滴的传热计算对核电站的安全性具有重要意义。本研究采用移动粒子半隐式(MPS)方法对该过程进行模拟。为了对该过程中冷凝液滴传热传质界面的识别进行改进和优化,提出一种基于全局扫描的自由表面识别方案,将该方案以及其他3种典型的自由表面识别方案应用于冷凝液滴撞击液面问题。结果表明:采用粒子数密度法的自由表面识别方案、采用法向量扫描的自由表面识别方案和采用弧度法的自由表面识别方案皆因其方法本身的缺陷而无法精确地对液滴自由表面进行识别;而采用全局扫描的自由表面识别方案,能克服上述方法的缺陷,准确地对自由表面粒子进行识别,且其求解得到的压力场与物理实际最为接近。这种新型的基于全局扫描的自由表面识别方案为今后计算冷凝液滴交界面处传热传质问题打下了良好的基础。

关键词：冷凝液滴自然循环移动粒子半隐式法自由表面识别全局扫描