在线布流调节影响铸嘴型腔熔体流场和温度场的研究

建立了在线布流调节时铸嘴型腔熔体非定常流动和传热数学模型，应用数值方法仿真分析了入口速度斜坡变化时铸嘴型腔流场、温度场、压力场的动态演化过程。结果表明，对型腔进行在线布流调节来改善铸嘴型腔流场、温度场是可行的。     

基于Fluent的合金化炉保温段温度场的数值模拟

建立合金化炉保温段内空气流动与热交换的物理与数学模型,利用Fluent软件,采用标准κ-ε湍流模型,对合金化炉保温段内气体流场和温度场的分布进行数值模拟研究.经分析知模拟结果与实际情况较吻合,此方法对了解和控制合金化炉内的温度分布具有指导意义.     

油气润滑条件下电主轴轴承腔内多相流特性分析

基于油气润滑气液两相流理论,采用COMSOL Multiphysics仿真软件建立B7003CY/P4角接触球轴承腔内的油气两相流模型,分析轴承腔内气相流速、压力以及润滑油的分布。通过计算轴承的摩擦生热量以及腔内关键点的换热系数,分析轴承腔内温度场的分布。试验与仿真结果表明:润滑油沿着进油管道进入轴承腔内,大量的润滑油聚集在轴承腔内的前端,少许润滑油会随着空气进入轴承腔内,而进气速度影响润滑油的分布;轴承腔内的温度受电主轴的转速和进气压力影响,随着电主轴转速提高,摩擦产生的热量增多,轴承腔内的温度升高;进气压力越大,空气流速越大,轴承腔内的温度越低,且轴承腔内换热系数细化后得出的温度场更接近真实值。     

相场法定量模拟强迫层流对微观偏析的影响(英文)

采用耦合流场的相场模型,模拟Ni-Cu合金过冷熔体流动对液固界面前沿浓度分布的影响;定量分析强迫层流对迎流方向、垂直流动方向与逆流方向枝晶尖端前沿浓度边界层厚度,浓度最大值和枝晶微观偏析的影响。结果表明:溶质场和流场二者相互影响;枝晶上游侧浓度边界层的厚度较薄,溶质浓度的最大值较小;而枝晶下游侧恰好与此相反。贫Cu区域在迎流方向枝晶臂沿枝晶轴线方向的宽度较大,但Cu原子的浓度较低,微观偏析最严重,枝晶下游侧缩松倾向加剧。     

高参数金属波纹管集装式机械密封腔内流场动力学特性研究

以计算流体动力学(CFD)数值计算理论及方法为基础,对处于高速、高温、高压复杂工况的波纹管集装式机械密封装置腔内流场进行了数值模拟分析,得到了密封腔内介质的温度场、压力场、湍动能及流场区域涡量分布,分析了腔内流体的流动及传热动力学特性,为动、静环温度场的热流固耦合数值算法提供依据.     

超声及电磁场对铝合金熔体影响的数值模拟及试验研究

针对铝合金熔体的超声及电磁搅拌处理过程,创建了超声场、电磁场、流场和温度场的数学模型,并采用COMSOL Multiphysics软件求解模型,得到了超声场、电磁场和超声/电磁复合场对铝合金熔体内流场和温度场的分布规律,并通过试验对模拟结果进行了验证。结果表明,增加超声功率使得声压幅值和流场的流动速率均随之增加,同时会使熔体的温度梯度逐渐减小;施加电磁场后产生的电磁搅拌改变了熔体的流动方向且使熔体的流动速率显著增大,这对熔体的温度分布产生了较大影响;在超声和电磁复合场下,电磁场比超声场对熔体流场和温度场的影响更大,且占主导地位。数值模拟结果和试验结果符合较好。     

Optimization of the Number of Burner Nozzles in a Hot Blast Stove by the Way of Simulation

The structure of the burner nozzles in a blast furnace hot stove including their number, location, and angle has a vital effect on the flow field, temperature distribution, combustion efficiency, etc. In this article, simulation models were established for the hot stove located at Shougang Qianan. The \( k{-}\varepsilon \) model, eddy dissipation model, and P-1 model were used for the modeling of turbulence, combustion, and radiative heat transfer, respectively. The effect of different number of burner nozzles on the flow field and temperature distribution in the combustion chamber was investigated. The results indicated that 19 or 21 burner nozzles were preferred to obtain the optimum flow field and temperature distribution.     

中空钢锭芯部压缩空气冷却能力的数值模拟

中空钢锭芯部压缩气体的冷却能力对于钢锭凝固过程有显著影响,也是凝固模拟的关键边界条件。用计算流体力学方法计算了芯部压缩气体湍流流动的速度、压力和换热系数的分布。分析了气体滞止压力、内套筒壁面温度和环隙宽度对换热系数的影响,并将数值模拟结果与解析模型的结果做了对比。计算结果可以用来指导芯子结构设计。     

高速列车框架焊接的双椭圆柱高斯分布热源模型

根据高速列车车体结构焊接工艺特点,分析并改进常用高斯热源,提出适用于铝合金惰性气体保护焊接（MIG）的双椭圆柱-高斯分布热源模型.该热源模型基于焊接速度移动,形成的熔池表面为双椭圆形状,热流密度沿厚度方向均匀分布,在径向呈高斯-双椭圆分布.基于热源模型的数学表达,以有限元方法实现了热机耦合的焊接过程仿真,与薄板试验结果比较,温度场分布与降低趋势较好地吻合;拉应力峰值出现在熔合线和热影响区,仿真值、试验值分别为88.8,85 MPa.结果表明,该热源模型有效地模拟焊接温度场时域上的变化过程,准确地预测结构变形、残余应力分布规律,应用于高速列车头车框架结构焊接工艺优化及残余应力评估,为高速列车焊接质量控制及焊接工艺参数选择提供理论指导.     

Numerical calculation of thermal field and heat transfer coefficient for 160 kA aluminum reduction cell

1　INTRODUCTIONThetechnologiesofthe 16 0kA prebakedanodealuminumreductioncellofGuizhouAluminumSmelter,China ,wereintroducedfromJapaninthe1970 s .Ithasbeenfoundintherealoperationthatthetargetindexesarenotasgoodasexpected .Forexample ,thecurrentefficiencyislowerthan 88%andtheDCpowerconsumptionforproducingAlishigherthan 14 0 0 0kWh/t .Meanwhile ,becauseofthebiggersidechannel,sideledgecannotbefullyformed .Itisanalyzedthatpoorbusbararrangementsandinnerliningstructureaswellasoperationallha…     

Development and application of coupling model of aluminum thin-gauge high-speed casting

Based on the analyses of aluminum melt flow, solidification, heat transfer during the process of twin-roll casting, a coupling mathematical model of aluminum thin-gauge high-speed casting was developed, which included the casting roller shell. At the same time, Galerkin method was adopted to solve the coupling model. The fluid field and temperature field of aluminum melt in casting zone, the temperature field and thermal stress field of roller shells were simulated by the coupling model. When the casting velocity is 7 m/min, and the thickness of strip is 2 mm, the circumfluent area comes into being in the casting zone, and the mushy zone dominates the casting zone, while the temperature of melt decreases rapidly as it approaches the rollers. The temperature of the roller shell varies periodically with the rotation of roller, and reaches the highest temperature in the casting zone, while the temperature of roller shell decreases gradually as it leaves the casting zone. The difference of thermal stress between the inner surface and outer surface of the roller shell is very large, and the outer surface suffers tensile-compressive stress.     

基于改进热源模型的铝合金MIG焊数值分析

采用CMOS高速摄像机检测和分析铝合金熔化极气体保护焊(MIG焊)熔滴过渡行为,确定MIG焊熔滴的过渡频率和速度.在理论分析MIG焊热源特性、热作用模式以及焊缝形貌前提下,从宏观焊接热过程出发,提出并开发了适用于MIG焊的组合体积热源分布模式,MIG焊电弧被处理描述为经典的双椭球体热源模型,熔滴能量作用模式被表示成均匀球体热源模型.同时,在均匀球体热源模型中加入了熔滴热能和动能,实现了熔滴对MIG焊熔池冲击作用的影响.基于上述热源模型,建立了铝合金MIG焊温度场有限元模型,对厚板铝合金MIG焊温度场进行了模拟.结果表明,模拟获取的焊缝熔合线走势及形貌和实际焊接结果相吻合,证明开发的热源模型能够准确描述MIG焊指状熔深特性和热传导过程.     

Numerical calculation and industrial measurements of metal pad velocities in Hall-Heroult cells

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Optimization of flow control devices in a tenstrand billet caster tundish

The physical model of a ten-strand billet caster tundish was established to study the effects of various flow control devices on the melt flow. Before and after the optimization of the melt flow, the inclusion removal in the tundish was evaluated by plant trials. The physical modeling results show that when combined with a baffle, the turbulence inhibitor, instead of the impact pad, can significantly improve the melt flow. A turbulence inhibitor with a longer length of inner cavity and without an extending lip at the top of the sidewall seems to be efficient in the improvement of the melt flow. Various types and designs of baffles all influence the flow characteristics significantly. The "V" type baffles are better than the straight baffles for flow control. The "V" type baffle with four inclined holes at the sidewall away from the stopper rods is better in melt flow control than the one with one inclined hole at each sidewall. The combination of a well-designed turbulence inhibitor and an appropriate baffle shows high efficiency on improving the melt flow and an optimal proposal was presented. Plant trials indicate that, compared with the original tundish configuration in prototype, the inclusions reduce by 42% and the inclusion distribution of individual strands is more similar with the optimal one. The optimal tundish configuration effectively improves the melt flow in the ten-strand billet caster tundish.     

高速电主轴用球轴承油气润滑温度场仿真与实验研究

基于局部热源计算轴承内部生热,考虑不同转速计算油气润滑下轴承滚道表面对流换热系数,采用Mixture多相流模型结合RNG k-ε湍流模型和Fluent软件动网格技术,建立球轴承两相流场模型,求解得到电主轴球轴承油气润滑温度场,分析轴承内部温度分布,给出最佳供油量的确定方法。对某高速电主轴用球轴承进行了油气润滑两相计算,结果表明:随着转速增大,轴承总摩擦生热率急剧增大,且转速越大,增长幅度越大;给定工况存在最佳供油量,且最佳供油量随转速增大而增大。最后通过电主轴轴承实验证明了该模型对油气润滑模拟的可靠性。     

外加磁场对镁合金焊接熔池形态的影响

以镁合金焊接熔池为研究对象,建立了移动热源作用下焊接熔池的三维数学模型. 利用大型通用有限元软件ANSYS将电磁场分析结果导入到热流场分析中,实现电磁场和热流场之间的耦合分析. 模拟了无外加磁场作用下以及外加磁场作用下镁合金焊接熔池的温度场分布和流体流动的速度矢量分布. 结果表明,外加磁场产生的电磁力驱动熔池中熔融的液态金属发生旋转运动,改变了液态金属原有的运动方式和传热方式,流体流动速度和流动范围增加,焊缝熔宽增大,熔深减小. 试验结果验证了模拟结果的可靠性.     

Numerical model and experimental observation for distribution of SiCp in electromagnetic-centrifugally cast composites

A two-phase numerical model coupled with heat transfer was presented to describe the radial distribution of SiC particles on centrifugally-cast metal matrix composite,and a transverse static magnetic field was concurrently imposed to induce electromagnetic stirring of the melt as it revolved with the mold.Meanwhile,experimental observations were also carried out to examine the radial distribution of SiC particles in pure aluminum.The effects of the imposed magnetic field,particle size and the matrix metals were discussed.The computational results show that the particles tend to be congregated by the centrifugal force,and both increasing the imposed magnetic field and decreasing the particle size tend to result in even distribution of the particles.With the magnetic field varying from 0 to 1 T and the particle size from 550 to 180 μm,a uniform distribution of the particles in the aluminum matrix can be obtained among the computational results.The matrix metal can also influence the particle distributions due to the difference in physical properties of metals.Experimental observation shows similar tendency of particle distributions in aluminum matrix influenced by magnetic field and particle size.However,the chilling effect from the mold wall results in an outer particle-free zone,which is not involved in the numerical model.     

Effect of electromagnetic parameters on melt flow and heat transfer of AZ80 Mg alloy during differential phase electromagnetic DC casting based on numerical simulation

Based on multi-physical field coupling numerical simulation method, magnetic field distribution, melt flow, and heat transfer behavior of a Φ300 mm AZ80 alloy billet during differential phase electromagnetic DC casting (DP-EMC) with different electromagnetic parameters were studied. The results demonstrate that the increase in current intensity only changes the magnitude but does not change the Lorentz force’s distribution characteristics. The maximum value of the Lorentz force increases linearly followed by an increase in current intensity. As the frequency increases, the Lorentz force’s r component remains constant, and the z component decreases slightly. The change in current intensity correlates with the melt oscillation and convection intensity positively, as well as the liquid sump temperature uniformity. It does not mean that the higher the electric current, the better the metallurgical quality of the billet. A lower frequency is beneficial to generate a more significant melt flow and velocity fluctuation, which is helpful to create a more uniform temperature field. Appropriate DP-EMC parameters for a Φ300 mm AZ80 Mg alloy are 10–20 Hz frequency and 80–100 A current intensity.

     

脉冲磁致振荡下纯铝凝固磁场与流场分布的数值模拟

脉冲磁致振荡可以细化金属晶粒,为了研究其作用机理,采用ANSYS有限元模拟软件对脉冲磁致振荡下纯铝凝固磁场与流场分布进行了数值模拟.模拟结果显示,由于电磁趋肤效应,线圈中脉冲电流只在熔体表面感应产生电磁力,且随时间出现指向内部的压力与指向外部的拉力交替变化,沿径向有指向熔体顶部与底部交替变化.交变电磁力可以振荡熔体表面率先析出的晶核而使之游离,增大熔体形核率.同时感应电磁力迫使熔体产生流动,会利于晶核的均匀分布与温度场、浓度场的均匀化.     

铝合金变极性等离子弧焊应力场数值分析

以传热学及热弹塑性有限元分析法为理论基础,利用ANSYS有限元分析软件,对铝合金变极性等离子弧焊接温度场、应力场进行数值模拟. 建立 "高斯+双椭球"热源模型,通过正反极性不同尺度热源模型的循环加载,实现对焊接温度场及其应力场较准确的计算;焊后在焊缝的纵、横方向选取不同的点进行残余应力实际测量. 结果表明,不同路径上焊接残余应力值其分布规律与理论基本相同;实际测量结果同计算结果进行比较,二者数值相差较小,说明数值分析的计算结果具有一定的理论指导意义.