垂直上升管内对流沸腾瞬态数值模拟及其两相流不稳定性预测

核电站蒸汽发生器二次侧为两相对流沸腾换热过程,在设计过程中须保证其不发生两相流不稳定性。本工作采用时域法对垂直上升管内两相流不稳定性进行研究,建立了垂直上升直管内流动沸腾过程的一维模型,并编制计算程序。采用该程序模拟了流动沸腾过程气液两相流密度波的不稳定性,给出两相流波动过程瞬态参数分布,由此分析了密度波不稳定发生的机理,并分析了质量流速、系统压力、入口过冷度对不稳定的影响。结果表明,与已有实验及理论结果相比,瞬态参数计算结果与实验结果符合较好,可较好找到不同工况下直管内气液两相流发生不稳定的边界,结果优于Khabenski线算图方法。     

Numerical Simulation of Stall Flow Control Using a DBD Plasma Actuator in Pulse Mode

A numerical simulation method is employed to investigate the effects of the unsteady plasma body force over the stalled NACA 0015 airfoil at low Reynolds number flow conditions.The plasma body force created by a dielectric barrier discharge actuator is modeled with a phenomenological method for plasma simulation coupled with the compressible Navier-Stokes equations.The governing equations are solved using an efficient implicit finitevolume method.The responses of the separated flow field to the effects of an unsteady body force in various interpulses and duty cycles as well as different locations and magnitudes are studied.It is shown that the duty cycle and inter-pulse are key parameters for flow separation control.Additionally,it is concluded that the body force is able to attach the flow and can affect boundary layer grow that Mach number 0.1 and Reynolds number of 45000.     

池式反应堆堆内流场数值模拟

以板型燃料组件池式反应堆为研究对象,采用计算流体动力学程序CFX5对堆内流场进行了数值模拟,结果表明:流过堆芯燃料组件的流速较大,在燃料组件出口位置流速达到最大值;无论是否带有围桶,堆内压降均主要集中在堆芯燃料组件上,入口流量增大,堆芯燃料组件上的压降随之增加;堆芯上部腔室和下部腔室的压力变化很小;在相同的入口流量下,带与不带围桶的堆芯进出口差压非常接近。     

数值堆结构力学高精细模拟的并行实现和优化技术

反应堆结构力学模拟是对堆芯组件的静动态形变位移和受力进行分析,以保证堆芯安全、稳定运行。不同于传统的结构力学模拟,本文结合异构超级计算机上的AMD GPU体系架构进行高精细大规模模拟。在数学物理模型方面使用有限元分析方法,通过充分利用反应堆组件的同构性,对单根组件或局部组件的网格数据进行坐标空间变换,自动生成全堆芯结构大规模网格文件,实现全堆芯百亿网格的剖分。采用共轭梯度法对具有正定特征的大规模稀疏刚度矩阵线性方程组进行高效数值求解,实现精细化分析获知全堆芯组件的应力应变空间分布状态。另外,采用数据预取和数据对齐的并行优化方法,使求解器计算性能提高了30%以上。模拟结果展示了该方法的可行性和正确性,并在计算核心数从9 504扩展至615 168时,对具有102亿网格规模的中国实验快堆（CEFR）全堆芯静力学问题进行计算,并行弱可扩展性达到53%。     

Simulation of Flow Around Cylinder Actuated by DBD Plasma

The electric-static body force model is obtained by solving Maxwell's electromagnetic equations. Based on the electro-static model, numerical modeling of flow around a cylinder with a dielectric barrier discharge(DBD) plasma effect is also presented. The flow streamlines between the numerical simulation and the particle image velocimetry(PIV) experiment are consistent. According to the numerical simulation, DBD plasma can reduce the drag coefficient and change the vortex shedding frequencies of flow around the cylinder.     

Calculation for Three-Dimensional Structures of Two-Phase Flow in Enlarged Flow Area

Superconducting tunnel junctions in use for X-ray detection ale expected to produce an excellent energy resolution. An inclusive model is employed to give an overview of the detector characteristics. This method is devised to implicitly take properties of superconductor materials into account. With introducing an empirical relationship between junction parameters, the detector characteristics such as signal magnitude and energy resolution are reproduced to an acceptable degree. This method gives a helpful suggestion for understanding the detector performance such as a Fano-like factor, and may also serve as a guide line for designing tunnel junctions.     

竖直圆管内气泡运动的大涡模拟研究

基于两流体模型框架,使用雷诺平均N-S方程(RANS)和大涡模拟(LES)两种湍流模型对竖直圆管内的绝热离散气 液两相流动进行数值模拟研究。计算结果表明,采用恰当的相间相互作用模型,两种模型的时均模拟结果同实验均符合较好。气泡的壁面聚集现象被准确预测,速度场预测也较为准确。与基于RANS的SST湍流模型相比,采用WALE亚网格应力的大涡模拟得到的结果同实验符合得更好,且大涡模拟可给出流动的瞬态细节。     

非线性振动下水平通道内气液两相流动研究

在地震等行为产生的非线性振动下,两相流体会影响回路传热并对装置结构进行冲击,因此对气液界面行为的把握对核安全具有十分重要的意义。本文通过将振动装置与两相流实验回路相结合的方法,对非线性振动下水平通道内气液两相流问题进行了实验研究。基于FLUENT平台,结合动网格模型及UDF编程手段建立了数学模型,并对数学模型进行验证。研究结果表明：模拟结果与实验结果具有很好的一致性;振动工况下气液两相流动形式不同于稳态工况,会出现更复杂的气液界面,主要流型有泡状流、弹状流、搅拌流、波状流及环状流;瞬时摩擦压降的波动幅度随振动幅度和频率的增大而增大,且与振动幅度相比,振动频率对其影响更大。     

Numerical Simulation of Tripolar Vortex in Dusty Plasma with Sheared Flow and Sheared Magnetic Field

This article presents a study we have made of one class of coherent structures of the tripolar vortex. Considering the sheared flow and sheared magnetic field which are common in the thermonuclear plasma and space plasma, we have simulated the dynamics of the tripolar vortex. The results show that the tripolar vortex is largely stable in most cases, but a strongly sheared magnetic field will make the structure less stable, and lead it to decays into single vortices with the large space scale. These results are consistent with findings from former research about the dipolar vortex.     

放射性废物热等离子体处理熔融炉温度分布数值模拟及熔渣玻璃化配方初步研究

目前核电厂放射性废物处理工艺具有高增容性的特点,为最终废物处置带来很大的压力。针对高增容的处理现状,介绍了放射性废物减容处理技术的研究重点——热等离子体技术;通过数值模拟分析热等离子体熔融炉内的温度分布,给出固定床熔融炉关键部位的最高可能温度约为1 445℃,结合可选耐火材料探讨了炉体建造的可实现性。选取核电站3种典型的放射性技术废物进行模拟玻璃化配方实验,在限定的熔融温度条件下,得到符合我国核行业标准要求的玻璃固化体。     

壁面性质对蛇形微通道流动特性的影响

采用CLSVOF方法,以空气和水为介质,对不同壁面性质的矩形截面蛇形微通道内气液两相流动进行模拟研究。验证模型的合理性后,改变粗糙度及雷诺数Re,讨论其对泊肃叶数Po和努塞尔数Nu的影响并分析其影响机制;改变壁面接触角及粗糙度,探讨其对微通道内流体流动的综合影响;由于蛇形微通道特有的回转弯道,针对几种具有不同壁面性质的通道组合情况对流体流动特性进行研究。计算结果表明,壁面粗糙度的增加对Po的影响高于Nu,且可强化传热;壁面粗糙度对亲水壁面与疏水壁面的影响效果相反;当直微通道为亲水性光滑壁面、回转弯道为疏水性粗糙壁面时,其传热效果更好。     

Two-Dimensional Fluid Simulation of Collisional Plasma sheath over rf Powered Electrode with Cylindrical Hole

The characteristics of collisional radio-frequency (rf) sheath dynamics over an electrode with a cylindrical hole is simulated by means of a self-consistent model which consists of two-dimensional time-dependent fluid equations coupled with Poisson equation. In addition, an equivalent-circuit model is coupled to the fluid equations in order to self-consistently determine relationship between the instantaneous potential at the rf-biased electrode and the sheath thickness.Two-dimensional profiles of the potential, the ion fluid velocity, and the distributions of the ion and electron densities within the sheath are computed under various discharge conditions, such as the discharge powers and the gas pressures. The results show that the existence of the cylindrical hole on the electrode significantly affects the sheath structure and generates a potential trap in the horizontal direction, which is particularly strong when the sheath thickness is comparable to the depth of the hole. Moreover, it is found that the collisional effects have a significant influenc eon the sheath characteristics.     

流量波动条件下圆管内流动换热特性数值研究

对流量波动条件下核动力装置系统圆管内流体的流动换热特性进行了数值研究,重点研究了波动周期、波动振幅两个因素对流动换热特性的影响。结果表明:流量波动时,通道内的摩阻系数和壁面换热系数均随时间周期性波动,且波动周期与流量波动周期相同;波动周期增加,摩阻系数波动幅值减小,壁面换热系数波动振幅变化不明显;相对振幅增加,摩阻系数波动幅值增大,壁面换热系数波动振幅增大。     

Numerical Simulation of Fluid Flow and Heat Transfer of Supercritical Fluids in Fuel Bundles

A supercritical water-cooled reactor (SCWR) was proposed as a kind of generation IV reactor in order to improve the efficiency of nuclear reactors. Although investigations on the thermal-hydraulic behavior in SCWR have attracted much attention, there is still a lack of CFD study on the heat transfer of supercritical water in fuel channels. In order to understand the thermal-hydraulic behavior of supercritical fluids in nuclear reactors, the local fluid flow and heat transfer of supercritical water in a 37-element fuel bundle has been studied numerically in this work. Results show that secondary flow appears and the cladding surface temperature (CST) is very nonuniform in the fuel bundle. The maximum cladding surface temperature (MaxCST), which is an important design parameter for SCWR, can be predicted and analyzed using the CFD method. Due to a very large circumferential temperature gradient in cladding surfaces of the fuel bundle, the precise cladding temperature distributions using the CFD method is highly recommended.     

基于OpenFOAM的过冷流动沸腾数值模拟

过冷流动沸腾现象被广泛应用于工业生产和动力系统中,对该现象的准确预测是两相流CFD模拟的重要研究方向。本文详细阐述了该模拟过程中的欧拉两流体模型及相关辅助模型,基于开源CFD平台OpenFOAM,模拟了4.5 MPa下竖直圆管内的过冷流动沸腾,得到了截面空泡份额、液相平均温度及壁面温度沿轴向的分布。计算结果与实验值符合良好,说明了模型的有效性和程序的正确性。本文可为在OpenFOAM中添加新的模型及开发新的求解器以模拟过冷流动沸腾问题提供参考。     

Coal Liquefaction by Using Dielectric Barrier Discharge Plasma

An innovative method for coal liquefaction by using dielectric barrier discharge (DBD) plasma in a short reaction time was developed. Using tetralin as the reaction medium, DBD plasma as the energy source, and a reaction time of 10 min at 140 o C, up to 10% of coal was converted to liquid material. The results showed the feasibility of coal’s liquefaction by DBD plasma under relatively moderate conditions. Simultaneously, it was clarified that the effect of DBD plasma treatment was opposed to the thermal effect of heating. An acid plasma sheath could be formed on the coal powder surface in DBD conditions, liquefied reactions could be carried out in the absence of inorganic acid, and the products were nearly neutral and with low causticity.     

蒸汽发生器实验回路倒流特性仿真分析

针对立式倒U型管蒸汽发生器传热管内出现的倒流现象,基于RELAP5/MOD3.3程序,采用新的控制体划分方案对蒸汽发生器实验段进行建模,模拟实验回路中发生的倒流现象。通过与实验数据进行对比分析,验证建模方案的正确性。在此基础上,分析倒流现象对蒸汽发生器实验段流动传热的影响。结果表明:倒流现象发生在较短管内,对于单个U型管,倒流管的流量高于正流管。倒流发生后,系统进入相对稳定状态,但蒸汽发生器实验段的换热功率和进出口腔室负压降绝对值显著降低。     

Degradation of Acid Orange 7 Dye in Two Hybrid Plasma Discharge Reactors

To get an optimized pulsed electrical plasma discharge reactor and to increase the energy utilization efficiency in the removal of pollutants, two hybrid plasma discharge reactors were designed and optimized. The reactors were compared via the discharge characteristics, energy transfer efficiency, the yields of the active species and the energy utilization in dye wastewater degradation. The results showed that under the same AC input power, the characteristics of the discharge waveform of the point-to-plate reactor were better. Under the same AC input power, the two reactors both had almost the same peak voltage of 22 kV. The peak current of the point-to-plate reactor was 146 A, while that of the wire-to-cylinder reactor was only 48.8 A. The peak powers of the point-to-plate reactor and the wire-to-cylinder reactor were 1.38 MW and 1.01 MW, respectively. The energy per pulse of the point-to-plate reactor was 0.2221 J, which was about 29.4% higher than that of the wire-to-cylinder reactor （0.1716 J）. To remove 50% Acid Orange 7 （AO7）, the energy utilizations of the point-to-plate reactor and the wire- to-cylinder reactor were 1.02×10^-9 mol/L and 0.61×10^-9 mol/L, respectively. In the point-to- plate reactor, the concentration of hydrogen peroxide in pure water was 3.6 mmol/L after 40 min of discharge, which was higher than that of the wire-to-cylinder reactor （2.5 mmol/L）. The concentration of liquid phase ozone in the point-to-plate reactor （5.7×10^-2 mmol/L） was about 26.7% higher than that in the wire-to-cylinder reactor （4.5×10^-2 mmol/L）. The analysis results of the variance showed that the type of reactor and reaction time had significant impacts on the yields of the hydrogen peroxide and ozone. The main degradation intermediates of AO7 identified by gas chromatography and mass spectrometry （GCMS） were acetic acid, maleic anhydride, p- benzoquinone, phenol, benzoic acid, phthalic anhydride, coumarin and 2-naphthol. Proposed degradation pathways were elucidated in light of the ana     

InfluenCe of Downstream Flow on Conduction Phase of Coaxial Plasma Opening Switch

Plasma behaviour and the scaling relations in a coaxial plasma opening switch （POS） using hydrogen plasma are studied self-consistently based on the two-dimensional magnetohydrodynamic （MHD） equations in conjunction with the generalized Ohm＇s law. The vacuum region on the right of POS is included in the model and the influence of downstream flow on the conduction characteristics is discussed. It is found that with the penetration of magnetic field, the pure hydrogen plasma is pushed downstream significantly; and POS still conducts current after the magnetic field arrives at the load edge of POS, which is different from the previous experimental results in a multispecies POS. It is because that the noticeable downstream plasma in the pure hydrogen POS may continue to conduct the current, while in the multispecies POS, the downstream plasma is unimportant so that the conduction phase ends soon after the magnetic field reaches the load edge. The scaling relation obtained from the simulations including the downstream region is consistent with the experimental results.     

基于多孔介质模型的行波堆TP-1堆芯稳态温度场与流场数值模拟

根据TerraPower公司最新设计的钠冷行波堆TP-1的具体结构和运行特点,采用多孔介质模型,使用商用软件CFX对行波堆堆芯的热工水力特性进行数值模拟,得到了TP-1稳态运行条件下堆芯温度场、速度场和压力场分布。结果表明：应用多孔介质模型对行波堆堆芯进行三维热工水力数值模拟的方法直观、快速、有效,将它应用于行波堆堆芯稳态条件下三维流场和温度场分析具有一定的意义。