可逆流体换向装置内部流场的数值模拟

以N-S方程和RNGk-ε紊流模型为基础,针对压冲时的可逆流体换向装置,模拟考察了入流速度、面积比、出流结构形式、引流间隙长度对内部流场的影响,并以引流率为标准将模拟结果与试验结果进行了对比。研究结果表明:根据计算流体力学(CFD)方法所得的模拟结果与试验结果之间的误差较小;面积比为1.5、出流结构采用扩散管形式、引流间隙为7 mm和10 mm时,引流效果较好。     

可逆流体换向装置一些基本问题的试验研究

可逆流体换向装置是决定气动式脉冲液体射流泵的流体输送效率的关键组成部件。通过试验研究了不同入流结构、不同出流结构、面积比、引流间隙等因素对可逆流体换向装置输送性能的影响。结果表明:较大的入流射流出口速度可以产生更好的引流效果;带较长接收管的出流结构总体上的流体输送效果不如无接收管的出流结构;由于涡流分离导致的沿壁返流,过大的面积比将导致引流效果变坏,最优面积比值选取1.5为宜;当引流间隙长度和出流结构入口直径的比值为0.9~1.0时,不同出流结构的引流效果均较好。     

15 keV~1.5 MeV单能光子及窄谱系列H*(10)/Kα转换系数的蒙特卡罗模拟

为克服由于不同标准实验室内X、γ射线照射装置所用X射线管型号及整体结构不相同,导致转换系数产生一定偏差的问题,本研究采用MCNP5程序建立照射装置模型,计算15 keV~1.5 MeV单能光子及N-40~N-200窄谱系列对应的H*(10)/Kα转换系数;利用自主研制的H*(10)次级标准电离室测量辐射场参考点处周围剂量当量率并作为参考值,与转换系数法进行对比以验证转换系数法计算结果的正确性。结果表明,蒙特卡罗模拟转换系数与ISO 4037-3推荐值的相对偏差在±4%以内,转换系数法与次级标准电离室法测量结果的相对偏差在3%以内,证明利用蒙特卡罗方法计算H*(10)/Kα转换系数可行,对于“非匹配参考辐射场”,可使用此方法进行周围剂量当量定值。     

核动力装置强迫循环与自然循环过渡过程特性研究

针对某型压水堆核动力装置,建立反应堆及一回路系统强迫循环与自然循环的计算分析模型,并与试验值进行比较,验证了建立的模型计算精度高,满足工程分析的要求.利用建立的数学模型,对自然循环与强迫循环过渡过程进行分析计算,结果表明:强迫循环向自然循环转换过程中冷却剂流量、蒸汽发生器压力、反应堆出口温度是几个约束参数;自然循环向强迫循环的转换过程中反应堆功率变化与周期变化幅度较大.     

裂片核素在岩石中的迁移研究

研究了＾１２５Ｉ在花岗岩中的吸附动力学，结果表明在实验条件下＾１２５Ｉ吸附极少，由测得的渗透曲线和流量曲线经物料衡算，求得岩石输出浓度与时间的关系曲线。利用分布函数，求得纵向弥散系数Ｄ、孔隙流速ｖ和有效孔隙率εｅ。提出了＾１２５Ｉ在花岗岩中迁移的数学模型方程，并求解得到核素浓度随时空变化的分析解和数值解。     

铅铋介质闭式换向器运行特性与水锤现象研究

为研究闭式换向器在液态铅铋合金（LBE）介质换向过程中的流量稳定性及其适用性,采用FLUENT软件结合重叠网格方法对三通切换阀形式的闭式换向器换向时上游的压力与速度波动进行计算分析。结果显示,换向过程中,阀芯启动及停止运动时产生水锤,水锤波以介质声速在管道中传播,从而影响管道内压力和速度的分布,水锤波的峰值大小与介质密度、阀芯运动速度成正比,水锤波频率不受阀芯运动速度影响。由于水锤波的波峰值较大,使此类型闭式换向器在LBE下换向动作时上游管道难以维持稳定流量并威胁装置安全,故在LBE流量标定装置中不适用。     

基于动态模拟与比例控制的液滴曳力系数计算方法研究

液滴的曳力系数是影响液滴行为的关键因素,尚未有成熟的通用计算公式。提出一种计算液滴曳力系数的方法:动态模拟液滴在均匀气流中的运动,通过加入动量方程的体积力源项,对液滴质心位置进行控制,使液滴做近似简谐运动,根据运动过程中的位置变化估算曳力系数。采用流体体积函数(VOF)方法模拟液滴-气体两相流,实现了此方法。通过几个算例,验证了此方法,计算结果表明,与高效的比例积分微分(PID)控制方法相比,此方法具有参数选取简便,计算效率更高的优点。     

秦山核电厂排风烟道流量测量皮托-文丘里复合管的研制

介绍一种用于核电厂排风烟道流量测量仪表——皮托-文丘里复合管。该表能在低的气体流速下得到较大的差压信号,差压值随流速变化率大、灵敏度高、阻力损失小。该表置于烟道中心区。从流体力学观点导出该表的放大倍数和流量系数的解析关系式。根据相似理论及流体流动具有稳定性和自模性的特性,通过1/12烟道模型试验找出实际烟道中心的流速与平均流速的关系。再根据排风烟道的流量范围,把皮-文复合管在回流风洞上标定,最后给出了可供烟道流量测量用的流量系数。这是常规仪表难于实现的。     

矩形通道内脉动层流相位差实验研究

对流量脉动条件下矩形通道内的相位差进行了实验研究，通过建立的脉动层流相位差数学模型，对脉动周期、脉动振幅、通道结构尺寸和流体性质等因素进行了分析，并将实验数据与理论模型结果进行对比。结果表明：矩形通道内，脉动层流的流量变化滞后于压降变化，存在相位差，该相位差仅与脉动周期、流道结构尺寸和流体性质有关，与压降相对振幅无关。     

裂片核素在岩石中的迁移研究Ⅲ．纵向弥散系数的测定和核素~（129）Ⅰ的迁移模型

研究了￣（１２５）Ⅰ（模拟裂片核素￣（１２９）Ⅰ）在花岗岩中的吸附动力学，结果表明在实验条件下￣（１２５）Ⅰ吸附极少。由测得的渗透曲线和流量曲线经物料衡算，求得岩石输出浓度与时间的关系曲线。利用分布函数性质，求得纵向弥散系数Ｄ、孔隙流速ｖ和有效孔隙率ε＿ｅ。提出了￣（１２９）Ⅰ在花岗岩中迁移的数学模型方程，并求解得到核素浓度随时空变化的分析解和数值解。     

高温气冷堆备用停堆装置新型供料器分析与试验

吸收球停堆装置参与球床型高温气冷堆的堆芯反应性调节控制,实现反应堆冷停堆,供料器是数百万个6 mm吸收球从堆芯反射层被气力输送回到贮球罐的起点,吸收球在供料器中被气流悬浮、加速,需研究不同结构型式的供料器的输送性能及可靠性.利用Fluent软件对新型流化管式供料器进行了数值模拟分析,获得速度、压力分布场,同时进行了空气介质常温流动供料器试验研究.模拟计算得到供料器局部阻力系数约为5.1,试验测得供料器局部阻力系数为5.7,结果在工程应用可接受的范围内.     

Control of flow separation over a wing model with plasma synthetic jets

An array of 30 plasma synthetic jet actuators (PSJAs) is deployed using a modified multichannel discharge circuit to suppress the flow separation over a straight-wing model. The lift and drag of the wing model are measured by a force balance, and the velocity fields over the suction surface are captured by a particle imaging velocimetry system. Results show that the flow separation of the straight wing originates from the middle of the model and expands towards the wingtips as the angle of attack increases. The flow separation can be suppressed effectively by the PSJAs array. The best flow control effect is achieved at a dimensionless discharge frequency of F⁺ = 1, with the peak lift coefficient increased by 10.5% and the stall angle postponed by 2°. To further optimize the power consumption of the PSJAs, the influence of the density of PSJAs on the flow control effect is investigated. A threshold of the density exits (with the spanwise spacing of PSJAs being 0.2 times of the chord length in the current research), below which the flow control effect starts to deteriorate remarkably. In addition, for comparison purposes, a dielectric barrier discharge (DBD) plasma actuator is installed at the same location of the PSJAs. At the same power consumption, 4.9% increase of the peak lift coefficient is achieved by DBD, while that achieved by PSJAs reaches 5.6%.     

关于一维两流体模型中界面阻力计算的研究

一维两流体模型中,界面阻力是决定相间耦合程度的关键参数,其计算方法目前有漂移流模型法和阻力系数法。本研究利用子通道程序,基于圆管空气-水两相实验数据,对这2种计算方法进行了评估,结果表明一维两流体模型中漂移流模型法的预测能力要优于阻力系数法。同时评估了两相流动中分布效应对界面阻力计算的影响,结果表明在低空泡份额区分布效应影响较小,而高空泡份额区其影响明显。      

5×5棒束通道内流动转捩特性研究

棒束通道的特殊结构导致其内部流动转捩情况较为复杂,探究其内部流动转捩规律具有重要意义。本文针对棒束通道内的流动转捩特性开展实验与CFD模拟研究,通过实验获得了棒束通道内沿程阻力系数的变化规律;采用不同湍流模型进行了数值模拟。结果表明,SST k-ω模型能较好地反映实验结果。进一步对比了不同雷诺数工况下通道内不同位置的沿程阻力系数与湍流强度,发现对于不同子通道,中心子通道湍流强度与沿程阻力系数高于边角子通道;对于同一子通道,子通道中心处湍流强度与壁面切应力高于子通道边缘处。这一结果说明,受壁面影响,棒束内湍流强度、壁面切应力、阻力特性具有不均匀性,这些空间上的不均匀性相互作用会引起总体上棒束转捩点不明显。     

常温下氙在椰壳活性炭上的吸附性能

利用脉冲进样气相色谱法研究椰壳活性炭常温吸附Xe的性能,获得了氙在椰壳活性炭上的吸附系数与温度、气体流速、Xe浓度的关系。研究结果表明：在20～50℃温度范围内,温度每升高1℃,Xe的吸附系数下降3%;气体流速在5～10cm/s范围内,Xe的吸附系数不受气体流速影响;气流中Xe浓度小于10^-3mL/mL时,其吸附系数亦不受影响。     

Flow Transition Characteristics in 5×5 Rod Bundle Channel

The special geometric structure of the rod bundle channel can induce complicated flow transition of the coolant, and investigation on the flow transition rules is sufficiently important. In the current study, experimental and numerical study on the flow transition characteristics in the 5×5 rod bundle channel was carried out. Experiments were performed to obtain the variation characteristics of the resistance coefficient and CFD simulation was performed using different turbulence models in ANSYS Fluent. The results show that the simulation with SST k-ω turbulence model agrees well with the experimental data. The simulated turbulence intensity and resistance coefficient at different measurement locations and in different flow conditions were compared. For different subchannels, the turbulence intensity and the resistance coefficient are higher in the center subchannel than those in the edge subchannel. For the same subchannel, the turbulence intensity and the shear stress in the subchannel center are higher than those in the subchannel edge. This result indicates that the turbulence intensity, shear stress and resistance coefficient in the rod bundle are not uniform due to the influence of the wall surface. This non-uniform spatial interaction makes the transition point obscure.     

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.     

模块式高温气冷堆核能系统二回路流体网络控制特性分析

针对模块式高温气冷堆（MHTGR）核能系统二回路流体网络进行非线性建模,研究管路动力学特性及网络拓扑结构特性,建立了微分-代数模型,设计了模块质量流量和汽机主蒸汽压力的调控方案。在MATLAB/Simulink环境下对模型进行标准化封装,以高温气冷堆核电站示范工程（HTR-PM）为例进行二回路流体网络的仿真。结果表明,模型有效地反映了系统二回路流体网络的非线性特性,设计的控制器使得模块流体质量流量和汽机主蒸汽压力有效地收敛于参考值,各项控制指标均高于控制要求。设计的仿真平台可为实际工程调控中积分时间系数的选择、拥有更多模块数量的高温气冷堆核能系统二回路流体网络的调控等提供试验仿真测试。     

Theoretical research on the transport and ionization rate coefficients in glow discharge dusty plasma

The electron kinetic model for investigating the transport and ionization rate coefficients of argon glow discharge dusty plasma is developed from the Boltzmann equation.Both of the electron-neutral and electron-dust collisions are considered as collision terms in the kinetic equation.The kinetic equation is simplified by employing the local approximation and nonlocal approach under the same discharge conditions,and the corresponding simplified kinetic equations are known as local and nonlocal kinetic equations respectively.Then the electron energy distribution function(EEDF)is obtained by numerically solving the local and nonlocal kinetic equations and the dust charging equations simultaneously.Based on the obtained EEDFs,the effective electron temperature,electron mobility,electron diffusion coefficient and ionization rate coefficient are calculated for different discharge conditions.It is shown that the EEDFs calculated from the local kinetic model clearly differ from the nonlocal EEDFs and both the local and nonlocal EEDFs are also clearly different with Maxwellian distributions.The appearance of dust particles results in an obvious decrease of high energy electrons and increase of low energy electrons when axial electric field is low.With the increase of axial electric field,the influence of dust particles on the EEDFs becomes smaller.The electron mobility and diffusion coefficients calculated on the basis of local and nonlocal EEDFs do not differ greatly to the dust-free ones.While,when dust density nd=10^6 cm^?3,the electron mobility increases obviously compared with the dust-free results at low axial electric field and decreases with the increasing axial electric field until they are close to the dust-free ones.Meanwhile,electron diffusion coefficients for dusty case become smaller and decrease with the increasing axial electric field.The ionization rate coefficients decrease when dust particles are introduced and they approach the dust-free results gradually with the increasing axial electric field.     

矩阵分裂算法在两相流方程求解中的应用初步研究

矩阵分裂算法是一种有限差分方法,根据系统特征值的正负,确定对流项差分格式,能描述流场信息传播的真正方向。本文基于隐式矩阵分裂算法对两相流均相流模型进行离散,利用矩阵形式追赶法求解离散后的块三对角矩阵,运用FORTRAN90程序实现数值求解过程。运用喷管内流动和两相可压缩性实验两个基准题对算法进行校验,计算结果和解析结果吻合良好,证明求解方法的可靠性。本文成功运用矩阵分裂算法求解两相流模型,为热工水力计算程序的开发和改进提供了新的视角。