核电厂蒸汽发生器传热管束流弹失稳评价关键参数分析及实验研究

针对某压水型核电厂新研发蒸汽发生器的传热管，采用ASMEBPVC-Ⅲ推荐的半经验公式及相应参数取值，计算得到了悬臂传热管在空泡份额为0%（单相水）、10%、20%、50%、80%、90%下的流弹失稳临界流速。同时，设计开展了悬臂传热管阵在各空泡份额下的流致振动实验，测得了传热管流弹失稳临界流速、动水中的振动阻尼比及固有频率等关键参数。实验中测得的振动阻尼比主要包含了两相阻尼与粘滞阻尼，随空泡份额的变化而变化，范围为1.51%～3.98%，考虑测量不确定度后，该值可用于本文所述蒸汽发生器设计，且具有一定的保守性。分析结果表明，规范推荐的公式及参数计算所得传热管流弹失稳临界流速和实验结果趋势相同、规律一致，前者较后者有较大的保守性，安全系数在1.5以上；采用实验测得的阻尼比及固有频率重新计算得到的临界流速安全系数有所下降，但仍高于1.1。通过实验和分析，讨论了文中所述新研发核电厂蒸汽发生器传热管束流弹失稳评价关键参数取值及分析方法的合理性与保守性，可用于工程产品的设计及分析。     

压水堆燃料组件附加质量仿真研究

为了准确探究反应堆冷却剂与燃料组件间存在流固耦合行为对燃料组件振动特性的影响,本文采用计算流体动力学（CFD）软件Fluent平台,运用其中的动态网格技术,以压水堆燃料组件为研究对象,通过建立燃料组件模拟棒束、堆芯围板以及冷却剂模型,实现燃料组件与堆芯围板分别单独运动工况的燃料组件附加质量计算。结果显示：燃料组件运动工况下,燃料组件附加质量系数均值为2.4712;围板运动工况下,燃料组件附加质量系数均值为–3.4713,均与文献值偏差小于5%。叠加附加质量后,燃料组件振动频率计算值与水中振动试验测试结果偏差小于5%,验证了分析方法的合理性。本研究建立的仿真计算方法能够用于压水堆燃料组件附加质量计算。     

不可压缩粘性流中板状梁的振动附加质量及阻尼

采用小参数展开法研究水口水槽中板状多跨梁与水槽底形成小间隙对梁的固有动特性，导出了梁振动时流体的附加质量系数和附加阻尼系数的解析表达式，并通过对频率的计算值与实验值的比较，间接验证了本文结果的正确性，得到了静水中多跨梁的固有频率随间隙值的变化规律。     

复杂流域中异型结构附加质量精细化计算方法研究

反应堆堆内构件工程设计通常采用附加质量方法模拟流体对结构的动力作用。以浸没在复杂流域中某异型压力管为例，提出了一种结构附加质量迭代计算方法，即以声固耦合分析得出的湿模态为基准，综合考虑流体密度和体积模量精细化确定结构附加质量，并讨论了该方法的适用范围。通过压力管1∶1振动试验实测与仿真结果对比，证明了附加质量精细化计算的准确性。结果表明，本文方法能较为精确地获得结构的主频和振型，具有较快的收敛速度，可供类似工程仿真分析参考借鉴。     

空间弯管管束固有频率及附加质量系数计算

在工程设计过程中,合理确定中间热交换器内空间弯管的固有频率和附加质量系数,对于该设备的安全稳定运行至关重要。本文旨在通过有限元方法计算中间换热器同心圆排布的管束在空气和液钠环境中的固有频率及附加质量系数。将管束分为3个典型区域,选取6个位置建立换热管和流体域的三维模型,计算换热管的固有频率和附加质量系数。结果表明,换热管在空气中的固有频率受空间弯管的弯曲半径影响较小,附加质量系数受空间弯管的弯曲半径和所处区域位置影响较大,近似三角形排布区域的管束固有频率最低,该区域内层换热管的附加质量系数最大。      

水在短同心套管内的湍流放热

本文介绍了试验迴路装置和同心套管试验段,在p为50—60公斤/厘米~2,t_f为55—106℃以及Re_f为(3.1—12.2)×10~4,Pr_f为1.65—3.10,q为4.50×10~5和7.35×10~5大卡/米~2·小时的条件下,测定了水在短同心套管内的湍流放热系数.并用通用准则关系式进行了数据处理,得出了轴向平均放热系数与轴向局部放热采数的计算公式.推荐公式的分散度不超过±8.5%.     

考虑流体作用的结构抗震分析

建立某型试验堆包括栅板组件和堆芯组件的堆内构件的完整有限元模型,采用完全二次组合法(CQC)模态组合方法对堆内构件进行谱分析,考虑堆芯在静水中附加质量对横向振动特性的影响,忽略水的附加质量对轴向的影响,由此建立2个有限元模型:(1)堆内构件在水中的近似模型,用于结构在横向地震载荷作用下的谱分析;(2)堆内构件在空气中的模型,用于结构在轴向地震载荷作用下的谱分析以及重力作用下的静力分析。分析表明,堆内构件满足ASME标准的要求。     

阻振质量对有限平板振动传递影响分析

建立点激励作用下附加阻振质量的有限平板理论分析模型,采用波动法和模态法的组合方法推导模型的振动响应。以均方速度为指标分析板系统附加阻振质量后,阻振质量对激励板的振动能量向接受板传递的阻抑规律,讨论阻振质量的质量比等参数对板系统振动阻抑效果的影响。结果表明,当附加条形阻振质量时,阻振质量在低频段对板系统的振动能量传递具有较好的阻抑效果。当附加离散阻振质量块时,阻振质量在低频段对板系统的振动不但没有阻抑效果,反而还会放大板系统的振动;在高频段,随着阻振质量质量比的增加,条形和离散阻振质量块对板系统振动的阻抑效果更好。     

快堆燃料组件抗震分析流体附加质量计算方法研究

浸没在液态钠中的快堆堆芯组件在地震作用下发生振动,可能导致组件结构损坏或堆芯结构变形,从而影响反应堆结构完整性和安全.流体使该振动表现为强烈的非线性,因此,研究地震引起的流固耦合效应对快堆抗震分析十分重要.本文主要研究流固耦合问题中附加质量的计算方法,该方法由Westergaard首先提出,是一种考虑水体对结构作用的简化动力学计算方法,它将动水压力等效成质量附加在结构上,质量等效原则自提出在各行业得到广泛应用,但缺乏详细理论推导.本文首先推导出附加质量公式,并对该公式进行有效性分析;接着对单根和两根组件用CASTEM在空气和水中进行建模;最后将频率、碰撞力分别与试验值比较.结果表明,计算值和试验值吻合.     

有界域轴向流动棒束流致振动附加质量力模型

基于Ｃｈｅｎ有界域静止流体中棒束流致振动数学模型，给出了有界域轴向流动中棒束流致振动的过程中附加质量力的具体表达式，并分析了棒束几何参数对流体力系数的影响。     

Numerical prediction of added mass and damping for a cylinder oscillating in confined incompressible gas–liquid two-phase mixture

This paper is concerned with the numerical analysis of the added mass and damping of a circular cylinder, which oscillates in an air–water bubbly mixture enclosed by a concentric shell. The mixture is assumed to be incompressible. This is because the oscillation frequency of the cylinder is low in this study, and accordingly the pressure change around the cylinder is not so large. An incompressible two-fluid model is solved by the finite element method, proposed by the author in a prior paper, to calculate the bubbly flow around the oscillating cylinder. The analysis reveals the effects of the diameter ratio of the cylinder to the shell, the air volumetric fraction and the bubble diameter. It also clarifies that the increase of damping ratio in the bubbly mixture is attributable to the phase lag of the drag force acting on the cylinder behind the cylinder displacement.     

双跨换热器传热管在静水中阻尼特性的研究

本文对双跨换热器传热管在静水中的结构阻尼与粘滞阻尼作了简介,并对在总阻尼中占主导地位的挤压膜阻尼作了较深入的讨论。Mulcahy 于80年代初提出的挤压膜阻尼数学模型是较为完善的,其缺陷是未计入管子振幅的影响,本文对它进行了修正。为了验证理论分析的结果,笔者对双跨传热管在静水中的挤压膜阻尼作了实验研究,得出挤压膜阻尼与中间支承板厚度、管子-中间支承板间隙以及管子振幅之间的关系。     

Damping Solitary Wave in a Three-Dimensional Rectangular Geometry Plasma

The solitary waves of a viscous plasma confined in a cuboid under the three types of boundary condition are theoretically investigated in the present paper.By introducing a threedimensional rectangular geometry and employing the reductive perturbation theory,a quasi-Kd V equation is derived in the viscous plasma and a damping solitary wave is obtained.It is found that the damping rate increases as the viscosity coefficient increases,or increases as the length and width of the rectangle decrease,for all kinds of boundary condition.Nevertheless,the magnitude of the damping rate is dominated by the types of boundary condition.We thus observe the existence of a damping solitary wave from the fact that its amplitude disappears rapidly for a → 0and b → 0,or ν→ +∞.     

Identification of damping mechanism of TRR-II reactor control rod during free fall insertion

In light water reactors, control rods are in general inserted into reactors by gravity. In order to achieve a rapid shutdown, it is required to insert control rods as fast as possible. On the other hand, a control rod with a fast falling velocity would impose a substantial impact to reactor structure as well as to the rod itself. Therefore, a damping force must come into effect, especially during the final stage of the free fall of the control rod. The purpose of this study is to develop a mathematical model and a numerical simulation to describe and identify the damping mechanism; and apply this model to the design of the control rod used in TRR-II reactor of the Institute of Nuclear Energy Research (INER) of Taiwan.The damping effect of a falling control rod comes from two factors: the viscous shear stress occurred in a narrow gap between the rod and an outer tube which confines the lateral movement of the rod, and the pressure force exerted on the rod by the compressed water under the rod. The viscous shear stress can be analyzed by assuming a couette flow between the rod and the outer tube similar to the viscous force occurred in rheology. In doing this, the flow rate in each flow path is closely related to the pressure gradient in the flow path and can be evaluated using an electrical circuit analogy. The results of the code prediction were compared to the experimental results as carried out by the INER. Finally, a parametric study was applied to estimate the effects of the various factors including gap thickness, size of the flow holes, and other geometric considerations on the rod falling velocity. The results of this study can serve some technical support during the stage of rod design and manufacture.     

均匀加热竖直管内强迫对流临界热流密度的实验研究

利用氟里昂－１２作为工作流体，对于均匀加热竖直管内强迫对流的临界热流密度（ＣＨＦ）进行了实验研究。在比较广泛的参数范围内对质量流速Ｇ，压力Ｐ和热平衡干度Ｘ对ＣＨＦ的影响进行了探讨。结果表明，干度和质量流速对ＣＨＦ的影响规律与其他作者获得的结果相类似。但压力对ＣＨＦ的影响规律比较复杂。压力的影响与质量流速、干度密切相关。即在不同的质量流速和不同的干度下，压力影响规律不同。当质量流速较高时，在低干度区ＣＨＦ随压力的升高而降低，干度较高时，ＣＨＦ随压力升高而增大。     

Three-dimensional dynamic response modeling of floating nuclear plants using finite element methods

A modelling technique which can be used to obtain the dynamic response of a floating nuclear plant (FNP) moored in an artificial basin is presented. Hydrodynamic effects of the seawater in the basin have a significant impact on the response of the FNP and must be included. A three-dimensional model of the platform and mooring system (using beam elements) is used, with the hydrodynamic effects represented by added mass and damping. For an essentially square plant in close proximity to the site structures, the three-dimensional nature of the basin must be considered in evaluating the added mass and damping. However, direct solutions for hydrodynamic effects with complex basin geometry are not, as yet, available. A method for estimating these effects from planar finite element analysis is developed.First, added mass and damping values are obtained from plane-strain finite element models of vertical cross sections through the platform. Fluid finite elements are used to model the seawater. For added mass calculations, the planar models include the platform cross section, the basin profile and the seawater in the basin. For hydrodynamic damping calculations, the planar model includes the platform cross section, the seabed and seawater, infinite in horizontal extent. Added mass and damping values are obtained for each significant mode of platform response. Estimates of three-dimensional added mass and damping are then obtained through combinations of the planar values. The release of the planar contraints of seawater motion and the reflection of gravity waves back to the platform are considered. Effective damping values applicable, on an average, for the entire response time are calculated for each plant mode of response. Since added mass and damping are frequency dependent, the selection of values to be used for a specific loading condition is usually an iterative process.The accuracy of the planar finite element model in obtaining two-dimensional added mass and damping is shown through comparison with existing and documented results. In addition, a comparison is shown for open ocean added mass and damping with a three-dimensional solution using velocity potential functions. It is concluded that the overall technique results in a reasonable and conservative calculation of the dynamic response of the floating nuclear plant.     

复合材料圆管阻尼特性研究

本文采用复模量方法的Timoshenko梁理论和模态应变能法的Love一阶壳理论建立了复合材料圆柱壳动力学方程,进行了相应的模态测试,并与有限元及试验结果进行对比。本文计算结果与有限元及试验结果符合良好。根据所建立的动力学方程,分析了梁理论的局限性,研究了铺层角度、长径比、厚径比、边界条件及环向波数对复合材料圆管阻尼特性的影响。结果表明：壳理论模型能对复合材料圆管的弯振阻尼特性进行准确分析,梁理论模型仅在轴向振动损耗占优的情况下比较准确;一弯模态损耗因子随长径比的增大而减小,在大于10时趋于定值;厚径比对一弯模态损耗因子影响较小;一弯模态损耗因子随铺层角度的增大先减小再增大后轻微减小,在铺层角度<30°和>75°时,双边固支边界的一弯模态损耗因子最大,在30°~75°之间时,悬臂边界的最大。     

Dynamic qualification of complex structural components of nuclear power plants

The safety requirements and the lack of accessibility for any future repair, impose the design requirement that the integrity of reactor components of nuclear power plants be assured for the lifetime of the plant. To meet this design requirement it is essential to qualify the component, i.e. prove its capability to perform the design function for the design life. In performing its design function, the component is subjected to both static and dynamic loads. The qualification for static loads is rather simple and reliable, but qualification for dynamic loads is complex and often uncertain. This is because analytical tools are often inadequate for a realistic dynamic qualification and exact structurally simulated experimental models are almost always difficult to build. In such a situation, methods using tests on simple experimental set-ups supplemented by conservative analytical back-ups must be evolved. This paper highlights the intricacies involved in the conservative dynamic qualification of the complex components by considering the example of the moderator sparger tube. This component is a perforated tube submerged in water and excited by flow. For such a case, a completely analytical or a totally experimental qualification is not possible. This paper describes a procedure by which the required dynamic characteristics such as added mass, damping and fluid forces are generated from simple experiments and the component is qualified by analysis using these data.     

Fluid-coupling coefficients in an array of hexagonal prisms

The study is related to the seismic analysis of fast breeder reactor cores.The first part of the paper describes an efficient method to compute the added mass coefficients in an array of slender bodies immersed in a fluid. It is assumed that the fluid is incompressible and non-viscous and that the flow is bidimensional. The Finite Element model uses one-dimensional elements with parabolic pressure field (three nodes per element) in the areas with small gaps, and two-dimensional elements elsewhere. The method is applied to an array of hexagonal prisms.The second part of the paper deals with the experimental determination of fluid-coupling coefficients in an array of hexagonal prisms. Both inertial and viscous couplings are investigated. It is found that the fluid damping depends critically on the gap size and that the cross-damping terms are small. The added mass coefficients are consistent with the numerical results of the 2D model. They are, however, 20 to 25% smaller, which is likely to result from axial leaks in the tests.Finally, the equation of motion of a seismically fluid-coupled system is briefly discussed. Some difficulties arising from the fluid are pointed out.