Numerical and Physical Simulation of Flow Patterns in a Swirling Flow Tundish

Swirling flow tundish is a new kind of tundish which has shown good effects on flotation of inclusion and reduction of inclusion content. In this paper, studies have been carried out on the flow fields in a one‐strand slab tundish. A full scale model of the flow patterns in the water model tundish was developed using a self‐developed code. RTD curves under different experimental conditions were obtained from both physical and numerical simulations. The effects of the swirling flow chamber geometry and the flowrate on flow patters in the tundish were discussed and compared with results from the numerical simulation. Validation of the self‐developed codes was achieved by comparing the physical and numerical results of the RTD curves and the mean rotational velocities in swirling flow tundish. As a result, significant rotational flow in the swirling flow chamber and asymmetrical flow pattern in the whole tundish were confirmed and the effects of these parameters on dead zone and mean residence time were also obtained. Further and more comprehensive studies are needed to optimize the design and application of such tundishes.     

六流连铸中间包内钢液流动的数值模拟

计算机模拟仿真作为一种参数优化的有效工具,在过程冶金中的应用已越来越广泛。对六流连铸中间包内钢水流动进行了计算机模拟研究后发现,原中间包设计存在不足,提出了优化的设想。     

Numerical and Physical Simulation of Tundish Fluid Flow Phenomena

The fluid flow in a continuous casting tundish is numerically and physically simulated by means of water models. Results of residence time distribution (RTD) measurements and laser‐optical measurements (Laser Doppler Anemometry – LDA, Digital Particle Image Velocimetry‐DPIV) are used to validate the numerical results for water before the numerical simulation is transferred to the steel melt. The investigations are focused on both steady‐state and transient casting conditions. To reduce vortexing and turbulence in the tundish different types of turbo‐stoppers are installed in the water models and their influence on the spacious flow structure is discussed. The turbo‐stopper produces higher turbulence in the inlet region of the tundish, but this region is spatially more limited in relation to the flow without turbo‐stopper. Thereby a more homogeneous flow is created at the outlet of the tundish with better conditions for particle separation. Basic design criteria for the geometry of a turbo‐stopper are developed. Moreover, the processes of first tundish filling and ladle change are simulated at a downscaled water model and these results are compared with numerical simulations using a Volume of Fluid (VoF) model. This multiphase model is able to reproduce the motion of gas bubbles and waves at the free surface.     

Numerical Simulation on Optimization of CSP Tundish Flow Field

Original scheme and optimizing scheme of WISCO CSP tundish have been simulated by software FLUENT. Flow field and temperature field of different schemes have been analyzed. The results which have been proved by hydraulic model experiments are the same with that of numerical simulation. It shows that the dead volume Vd of optimizing scheme decreases to 11.37%, reduced by 67.8% compared with the original scheme. The average residence time Ta of optimizing scheme increases to 639.2s, increased by 172.5s compared with the original scheme. The optimized scheme favors homogenous temperature distribution, more reasonable flow field and inclusions removing in the tundish. It is more adaptive to CSP plant of WISCO compared with the original scheme.     

小方坯连铸中间包流场温度场的数值模拟研究

采用湍流理论,建立中间包温度场的数学模型,计算获得了昆钢7^#小方坯连铸中间包耦合的流场及温度场,并研究了中间包在设置挡墙前后钢液流动及传热行为的变化。流场计算表明,使用合适的挡墙,钢液在中间包的停留时间变长,各水口处钢液的流动模式趋于一致;温度计算表明,设置挡墙后,各流钢液温度差异明显缩小。     

底吹氩中间包钢液流动特性的数值模拟研究

根据某厂实际中间包的操作工艺参数,采用欧拉两流体模型以及多孔介质模型,用数值模拟法研究了同时采用湍流控制器和气幕挡墙技术,中间包内气幕挡墙的位置及吹气量对中间包内钢液流动特性的影响。结果表明,采用气幕挡墙技术,吹气量及吹气位置对钢液流场及RTD曲线影响较大,吹气位置靠近人口或出口都不利于中间包钢液流动特性的改善,吹气量太大易引起表面卷渣现象,吹气量太小,不能形成有效的气幕挡墙。气幕挡墙距离人口1200～2000mm,且吹气量为0．90m^3／h时,可以有效延长钢液的停留时间,减小死区体积,有利于夹杂物的上浮去除。     

酒钢不锈钢板坯铸机中间包流场数值模拟

采用数值模拟方法,对不锈钢炼钢板坯铸机中间包结构进行分析,确定其设计的合理性,并对其设计参数进行优化,有效改善产品内在质量,提高经济性。     

连铸中间包控流装置优化数值模拟研究

针对板坯连铸机的中间包采用商业软件建立三维数学模型,计算不同中间包控流装置条件下中间包内的流场,分析不同方案对钢液流动状态和平均停留时间的影响,分析采用优化方案时钢中夹杂物的情况。结果表明,中间包控流装置的优化方案与原方案相比中间包的死区体积减少10.61%,中间包内开始出现示踪剂时间延长4.31%,均有利于中间包内钢液的混合和夹杂物上浮去除,同时采用优化方案钢中夹杂物水平能够满足生产工艺的要求。     

连铸中间包钢液流场的数模研究

以国内某钢厂连铸中间包为原型,通过数模研究表明:中间包内钢水人口区与本体之间设置合适的控流装置,可以抑制人口区强烈的湍流、减弱中包本体液面扰动.多孔高挡墙可以改善钢水流态、提高中包冶金效果.     

基于数值模拟的七流中间包控流装置设计

中间包内钢液流动行为是影响后续铸坯凝固质量的重要因素,因此,设计合理的中间包控流装置显得十分必要。以某钢厂新设计的七流"T"形中间包为研究对象,根据"T"形中间包结构特点和七流中间包的几何尺寸设计了四种不同的控流装置,并通过数值模拟的方法对各控流条件下中间包内的速度场、温度场和夹杂物去除效果进行系统分析,发现采用控流方案C时,各流间流动均衡性较好;中间包内最大温差和各流出口极限温差分别为9℃和0.4℃,温度非常均匀;同时,夹杂物去除率达89.12%,是适用于现场的一种理想控流方案。     

中间包自由表面的数值模拟与物理模拟

应用计算机数值模拟研究了坝高、堰深、坝堰间距以及液面高度对中间包自由表面的影响,并通过水力学模拟验证数值计算结果的正确性。实验证明,计算机模拟的结果与水模实验结果基本相符,说明计算机模拟结果可以满足工程的需要。为优化设计中间包、减少卷渣的发生提供了有利的依据。     

Numerical Simulation on Fluid Flow in Hot Metal Pretreatment

Basing on the commercial CFD metho d ,several models are adopted to simulate water model. The numerical simulation results are in good agreement with the experimental data of water model under the same experimental conditions. Then the numerical simulation method is presented to investigate the flow field, the vortex on gas-liquid surface and the uniform mixing time in hot metal ladles. This research shows: the vortex depth increases with increasing of immersion depth and rotation speed; Overflow appears in N=120rpm and h=3.2m; the turbulent kinetic energy increases with increasing immersion depth and rotation speed; uniform mixing time decreases with the decreasing of immersion depth and the rotation speed of stirring ; the optimal uniform mixing time is 23.5s on the conditions of N=100rpm and h=3.2m within the allowable range.     

方圆坯六流中间包控流装置的数值模拟与现场试验

基于数值模拟方法,对方圆坯弧形六流中间包在采用不同控流装置下进行模拟研究。数值模拟结果表明安装有导流孔V型挡墙+湍流器+挡坝控流装置的中间包更能有效地减少作用于弧形壁面的切应力、优化中间包流场、均匀温度分布、促使夹杂物去除。现场应用结果表明,采用所推荐控流装置的中间包,其相邻流温度均匀,温差均小于5 K,且最大平均温差仅为2.7 K;37Mn2平均总氧量T[O]为17×10-6;铸坯中氧化物夹杂物控制在50μm以下。     

五流非对称结构中间包流动及传热特征数值模拟

为优化某钢厂非对称结构中间包内流体流动、均匀各流钢液温度、延长近水口平均停留时间,以达到提高铸坯质量的目的,对工厂原方案及两个优化方案进行流场、温度场及停留时间的数值模拟计算.结果表明无控流装置的原中间包流动及温度场分布不合理,优化方案有了明显的改善,并确定了最佳方案.     

湍流控制器结构对中包流场影响的数模研究

根据某厂连铸中间包结构和操作工艺参数,选择LAM和Bremhorst修正的低雷诺数κ-ε湍流模型,建立了描述钢液流动的数学模型,用PHOENICS软件进行了模拟计算,讨论了湍流控制器结构对中间包流场的影响,指出湍流控制器的结构对中间包内流场的影响较大,其中环形带顶缘的湍流控制器最有利于中间包内钢液流动特性的改善,环形部分的曲率半径影响钢液的流动情况。     

六流中间包钢液流动及传热过程的耦合数值模拟

针对某厂六流特殊非对称型中间包温降严重的特点,采用耦合数值求解方法,计算并优化了中间包内的流场与温度场.结果表明:这种特殊中间包在未设控流装置时,入口与近端出口短路流严重,近端出口与远端出口的温差最大为8℃;优化后的中间包结构消除了短路流,均匀了各流钢液温度,最大温差降低到3.3℃,优化后的中间包能更好地满足生产的需求.     

中间包内流体流动及夹杂物去除的研究

采用湍流流动的数学模型方法,对板坯中间包内的钢液流动及夹杂物去除率进行了模拟研究。系统分析了在中间包内设置控流设备对钢液流动状态、平均停留时间以及夹杂物颗粒排除率的影响。结果表明,设置挡墙和坝后,中间包内有效防止了短路流,延长了平均停留时间,夹杂物整体排除率明显提高,大大改善了中间包的冶金效果。     

辊环离心铸造钢液流动和传热的数值模拟

建立了轧辊辊环卧式离心铸造钢液流动和传热的二维耦合模型,采用大型CFD软件FLUENT求解得到重力和离心力场下的流场、温度场分布和钢液偏心情况,并讨论了钢水流动对凝固过程的影响,分析结果对离心铸造的工艺设计有参考价值.     

中间包包型优化的数值模拟及生产应用

中间包包型对钢液流动有重要影响,进而影响中间包的冶金效果。利用数学模拟方法,以钢液停留时间分布曲线(RTD曲线)为评判标准,对某钢厂的中间包包型进行了优化改造,优化后出口浓度最大时间延长了200 s,钢液活塞区比例由39.3%增加至69.6%,死区比例由10.11%降至4.77%,且铸余减少3.5 t;包型优化后的大样电解夹杂物含量减少了72.35%。该包型于2008年12月开始在某钢厂稳定使用,提高了铸坯质量,节省了生产成本,为该钢厂创造了显著的效益。     

冷却壁液固两相流三维流动与污垢清洗数值模拟

建立了高炉水冷却壁三维物理模型。采用大型CFD软件FLUNT6.8中的欧拉多相流模型,对高炉水冷壁冷却埋管内的液固两相流三维流动和污垢清洗特性进行了数值模拟研究。分析了流体的流速、固体颗粒的粒径、体积分数对流体的流动、清洗强度及清洗均匀的影响。研究结果表明:流体的湍流强度、壁面污垢清洗强度和压力降均随流速、液固颗粒粒径和体积分数的增加而增加;液固两相流防垢除垢效果取决于流速、液固颗粒粒径和体积分数的合理组合;综合考虑节水节能及污垢清洗的均匀性,高炉冷却壁的最佳流速为1.5 m/s,固相颗粒粒径为3~4 mm,体积分数为5%~12%。研究结果为炼钢高炉冷却壁液固两相流污垢在线清洗的工业应用提供了理论基础。