AOD炉空气顶吹新技术

为了提高AOD炉的脱碳氧效率,减少还原用硅铁的消耗量,降低生产成本,日本新日铁公司对AOD炉进行了改造,增设了顶喷枪装置,向熔池喷吹空气,使AOD炉的脱碳氧效率在高碳范围中明显提高,硅铁单耗减少。     

侧吹气流的旋转对侧顶复吹AOD转炉熔池内流体混合特性的影响

基于在保证足够高的运动相似性下对非旋转气体射流120 t侧顶复吹AOD转炉内流体混合特性的研究,利用水模拟研究了套管式螺旋板型喷枪的旋转气体射流下AOD熔池内流体的混合特性。考察了侧吹气体射流的旋转和吹气量(侧吹和顶吹)及相邻两侧枪间夹角的影响。结果表明,在相同的吹气量下,旋转气体射流可提供更强烈的搅拌,提高混合效率。枪间夹角对流体流动和混合有更大的影响。与非旋转侧吹气流下的情况相类似,相邻两侧枪间的夹角由18°增至22.5°有利于熔池内液体的混合。顶吹气体射流会明显降低熔池内液体的混合效果。     

熔池特性对转炉熔渣流场的影响

采用流场数值模拟软件模拟了转炉熔渣溅渣护炉气化脱磷过程,探究了熔池深度和熔渣粘度对熔池流动的影响。结果表明,熔池深度越深,越有利于湍动能转换率的提高和熔池内的混匀,优化流场。死区占比随熔渣粘度的增高而增大,所以相应在高粘度深熔池中,需要增加喷吹时间才能使熔池达到稳定、均匀的效果。     

转炉型熔池内钢液流动数学模拟研究的进展

综述了现有转炉型熔池内钢液流动的一些数学模型,分析了有关模型的成功与不足,指出研究和开发切合实际的数学模型,对于掌握侧顶复吹AOD转炉熔池内钢液的流动特性具有重要的理论和实践意义.     

鱼雷罐倒T形喷吹脱硫水模试验研究

通过水力模型试验,分析了鱼雷罐倒T形喷吹脱硫过程中熔池内的流动状态,研究了工艺参数对鱼雷罐倒T形喷吹脱硫混匀时间的影响规律.结果表明,鱼雷罐倒T形喷吹脱硫过程中2支上升流股相互影响,会消耗部分能量,不利于搅拌动能的充分发挥;试验条件下,随着喷吹气体流量的增加,熔池内液体的混匀时间显著降低,当喷吹气体流量增加至3 m3/h后,混匀时间随喷吹气体流量略有增加;随着喷枪插入深度的增大,熔池内液体的混匀时间逐渐降低.     

多孔喷吹钢包内流动和混合过程的数学物理模拟

通过对多孔喷吹钢包内流动和混合过程的数学模拟和物理模拟，考察了六种不同喷吹方式下钢包内的流动及混合特征，提出了能获得以软吹且混合快为目的的喷嘴布置及考虑喷嘴个数影响的混合时间关系式。数学模拟与物理模拟的结果相一致．     

富氧底吹熔炼炉内氧枪结构参数的优化分析

以提高底吹熔炼炉反应区的熔炼效率及优化底吹炉反应区的氧枪结构参数为目标,运用数值模拟的方法,建立底吹熔池熔炼炉内气液两相流动的三维数学模型。应用正交表设计数值模拟的试验方案,以气含率、熔池内熔体平均速度以及平均湍动能为优化指标,采用田口方法对底吹熔池熔炼炉进行了氧枪结构多目标优化研究。结果表明,通过统计分析方法得到氧枪结构最优组合如下:氧枪直径为0.06 m,氧枪间距为0.98 m,氧枪倾角为17°。对优化结果进行统计验证,表明采用田口方法优化底吹炉氧枪结构可行,优化结果可靠。     

铸钢车间钢包脱气、脱硫新工艺

用钢包喷吹冶金法生产纯净钢水,在炼钢厂已成为标准化工艺.在铸钢工业中许多铸造车间用AOD法冶炼高质量高冲击性能的铸件.然而,铸造车间钢包冶金进展缓慢的两个原因是:在处理过程中小容量钢包的热损失严重和缺乏尺寸合适的浇包使用的喷吹设备.另外,高冲击值铸钢件在市场上也因其价格高而受到限制.由于低合金钢和普通碳素钢铸件需求量增加,而AOD法又耗资太多,因此采用最近开发的钢包喷吹设备,用碱性耐火材料冷砌钢包避免温度损失,和使用喷吹剂的新工艺在最近一年中进行了二百多炉冶炼.本文对产品改进性研制的方向和该工艺对硫、氮、总氧量降低的影响以及其后的对夏比冲击值的影响进行了讨论.     

偏心底吹熔池内三维流动的数值计算

本文给出一种分析液态金属熔池内熔液三维流动的方法,按照保角变换理论,建立了适合计算偏心喷吹时熔池流场的非规范型正交曲线坐标系,用速度分量及压力作为流场的求解变量,发展了在非规范正交曲线系下求解三维、不可压缩、定常时均湍流Navier-Stokes方程,连续性方程,k—ε双方程湍流模型方程的数值计算方法,预示出了熔池及其模型内的流动状态,计算的熔池模型流场的的速度值同实验结果很接近。     

吹氩精炼钢包内三维流动和混合现象的研究

利用开发的三维适体数值计算软件对吹气精炼钢包内的流动和混合过程进行了数学模拟，考察了操作参数对钢包内流动方式和混合的影响，提出了描述钢包内混合时间的代数表达式和合理的喷吹位置．数值模拟结果与实测值在定量上吻合较好．     

Numerical study of an ArH2 gas mixture flowing inside and outside a dc plasma torch

The flow of gas mixtures in a dc plasma torch is studied using the CFD PHOENICS (CFD PHOENICS, Berkeley, CA) code. In the model, the cold gas mixture (300 K), initially constituted of 85 vol% Ar and 15 vol% H, is introduced into a power input zone where it takes energy and is ejected in the surrounding atmosphere at constant pressure (10⁵ Pa). The flow is assumed to be in chemical equilibrium. Equations of mass, momentum, and energy are discretized using a control-volume method. The turbulent flow is modeled by a k-ɛ two-equations model for the turbulent kinetic energy and its dissipation rate. Finally, the algebraic coupling equations set is solved by means of the SIMPLEST algorithm, implemented into the CFD code, using a hybrid interpolation scheme. Results concern the effect of the torch power on the ArH₂ flow. The phenomenon is analyzed through the evolution of velocity and temperature inside and outside the torch. From these calculations, the effect of ambient gas entrainment by the jet is emphasized and a comparison of the level of entrained gas is made with experimental data.     

多喷嘴射流泵流场的数值模拟与PIV测量

为研究多喷嘴射流泵性能和内部流场特征,设计了不同结构的多喷嘴射流泵试验模型.采用k-ε湍流模型和壁面函数法对不同参数下的多喷嘴射流泵进行了数值模拟,模拟结果表明,喷嘴数和喷嘴角度及喉嘴距对射流泵工作性能影响较大;在吸入室及喉管入口处湍动能较大.利用PIV系统对不同结构射流泵内部流场进行了三维测量,获得了射流泵对称面流场的速度矢量和湍动能等值线图.试验结果表明,其速度梯度衰减得愈快,工作流体和被吸流体混合距离越短.验证了多喷嘴射流泵可缩短喉管长度.测量结果证明数值模拟的正确性,为多喷嘴射流泵理论研究和合理设计提供了理论依据.     

Computational fluid dynamic modeling of gas flow characteristics in a high-velocity oxy-fuel thermal spray system

A computational fluid dynamics (CFD) model is developed to predict gas dynamic behavior in a high-velocity oxy-fuel (HVOF) thermal spray gun in which premixed oxygen and propylene are burnt in a 12 mm combustion chamber linked to a parallel-sided nozzle. The CFD analysis is applied to investigate axisymmetric, steady-state, turbulent, compressible, and chemically combusting flow both within the gun and in a free jet region between the gun and the substrate to be coated. The combustion of oxygen and propylene is modeled using a single-step, finite-rate chemistry model that also allows for dissociation of the reaction products. Results are presented to show the effect of (1) fuel-to-oxygen gas ratio and (2) total gas flow rate on the gas dynamic behavior. Along the centerline, the maximum temperature reached is insensitive to the gas ratio but depends on the total flow. However, the value attained (∼2500 K) is significantly lower than the maximum temperature (∼3200 K) of the annular flame in the combustion chamber. By contrast, the centerline gas velocity depends on both total flow and gas ratio, the highest axial gas velocity being attained with the higher flow and most fuel-rich mixture. The gas Mach number increases through the gun and reaches a maximum value of approximately 1.6 around 5 mm downstream from the nozzle exit. The numerical calculations also show that the residual oxygen level is principally dependent on the fuel-to-oxygen ratio and decreases by approximately fivefold as the ratio is varied from 90 to 69% of the stoichiometric requirement. The CFD model is also used to investigate the effect of changes in combustion chamber size and geometry on gas dynamics, and the results are compared with the nominal 12 mm chamber baseline calculations.     

Analysis of a high-velocity oxygen-fuel (HVOF) thermal spray torch part 1: Numerical formulation

The fluid and particle dynamics of a high-velocity oxygen-fuel torch are analyzed using computational fluid dynamic techniques. The thermal spray device analyzed is similar to a Metco Diamond Jet torch with powder feed. The injection nozzle is axisymmetric with powder and a carrier gas injected on the centerline, premixed fuel and oxygen fed from an annulus, and air cooling injected from an annulus along the interior surface of the aircap. The aircap is a conically converging nozzle that achieves choked flow conditions at the exit; a supersonic, underexpanded jet develops externally. A two-dimensional, axisymmetric geometry is assumed; the equations for mass, momentum, and energy conservation are solved for both the gas and the particle phases. The combustion process is modeled using approximate equilibrium chemistry with dissociation of the gas with a total of nine species. Turbulent flow is modeled by a two-equation model for turbulent kinetic energy and dissipation rate that includes compressibility effects on turbulent dissipation. Particles are modeled as a lumped-heat-capacity system and are considered to melt upon attaining the required latent heat of fusion. An iterative, implicit, finite-volume numerical method is used to solve the coupled gas and particle equations inside and outside the torch. A companion paper presents the results of the numerical simulation and discusses in detail the gas and particle dynamics.     

Non-transferred Arc Torch Simulation by a Non-equilibrium Plasma Laminar-to-Turbulent Flow Model

Non-transferred arc torches are at the core of diverse industrial applications, particularly plasma spray. The flow in these torches transitions from laminar inside the torch to turbulent in the emerging jet. The interaction of the plasma with the processing gas leads to significant deviations from local thermodynamic equilibrium (LTE) far from the arc core. The flow from a non-transferred arc plasma spray torch is simulated using a non-LTE (NLTE) plasma flow model solved by variational multiscale (VMS) and nonlinear VMS (VMS_n) methods, which are suitable for unified laminar and turbulent flow simulations. Non-plasma turbulent jet simulations indicate that the VMS_n method produces results comparable to those by the dynamic Smagorinsky method, often considered the workhorse for turbulent incompressible flow simulations. VMS and VMS_n approaches are applied to the simulation of incompressible, compressible, and NLTE plasma flows in non-transferred arc torch operating at representative conditions found in plasma spray processes. The NLTE plasma flow simulations reproduce the dynamics of the arc inside the torch together with the evolution of turbulence in the produced plasma jet in a cohesive manner. However, the similarity of results by both methods indicates the need for numerical resolution significantly higher than what is commonly afforded in arc torch simulations.     

MATHEMATICAL MODELLING OF FLOW PHENOMENA IN METAL BATH COVERED WITH MOLTEN SLAG

By use of the two-component LDA and high speed camera,the water model of the flow fieldin metal bath under molten slag layer has been tested.On the basis of experimental results,theflow boundary conditions of liquid metal at the slag-metal interface of a gas injecting bathwere deduced.The flow field and the turbulent parameters of the metal bath covered with slagwere solved by the vorticity-stream function method.The results reveal that the flow velocity,turbulent energy and circulating rate of the melt under slag are lower than that of withoutslagcover.Another one “dead zone” of the lowest turbulent energy is formed in the top layerunder cover of slag near the ladle linning.     

射流倾斜角度对热轧无缝钢管冷却均匀性的影响

为了获得射流倾斜角度对热轧无缝钢管冷却效率及均匀性的影响规律,运用Fluent软件对单股倾斜射流冲击冷却热轧无缝钢管的流动特点及传热特性进行了有限元模拟。研究了不同射流倾斜角度下无缝钢管表面剪切力、湍流动能及压力分布特点,并获得冲击点处热流量及钢管1/2厚度处温度的变化曲线。结果表明,射流倾斜角度对钢管表面剪切力、湍流动能及温度分布具有显著的影响;随着射流倾斜角度的增加,钢管表面剪切力及湍流动能非对称性逐渐增加,且在顺流方向3°附近出现最大值;从钢管1/2厚度处温度分布发现,随着射流倾斜角度的增加,换热效率及温度均匀性得到了改善,先升高后降低;通过标准差计算,当入射角θ=10°时,冲击点两侧温度均匀性最佳。     

Contribution to the modeling of the interaction between a plasma flow and a liquid jet

A numerical simulation of the interaction between a plasma flow and a liquid jet was investigated, leading to the proposal of a compressible model, based on augmented Lagrangian, Large Eddy Simulation (LES) turbulence modeling and Volume of Fluid (VOF) approaches, capable of managing incompressible two-phase flows as well as turbulent compressible motions. The VOF method utilized volume markers to advect the local concentration of gas and liquid in a Eulerian manner. The numerical model was validated on single-phase plasma configurations as well as two-phase cross flow liquid jet interactions. Finally, an example of the first simulations of the interactions between a liquid jet and a plasma is presented. However improvements should be realized as to increase the speed of the VOF-SM algorithm or add specific subgrid models related to jet fragmentation and phase change.     

全幅二段电磁制动连铸复合钢坯的模拟研究

根据电磁连铸生产复合钢板的工艺原理，建立了一个数学模型来分析该工艺过程结晶器内两种异质钢液流动及分布特征。采用低Reynolds数湍流模型计算湍流参数，并以虚拟凝固壳来代替实际的凝固计算。根据对模拟结果的分析，提出了采用全幅二段恒稳磁场控制流动的方法。与文献中的实验结果对比证明了模型的可靠性。     

Numerical Modelling of Ar-N<Subscript>2</Subscript> Plasma Jet Impinging on a Flat Substrate

Substrate heating in the plasma spray process is one of the important parameters, which affects the microstructure of coatings and bonding between coating and substrate. In this study, a three-dimensional numerical model is developed to study the thermal exchange between the plasma jet and the substrate. The plasma jet temperature and velocity distributions and thermal flux to the substrate surface are predicted. The effects of arc current, gas flow rate, and stand-off distance on the temperature and velocity fields of the impinging plasma jet and thermal flux to the substrate are clarified. Results indicate that the three-dimensional effect has a very weak influence on the substrate heating. The air entrainment is compared for different cases. The present model is validated by comparing the present results with previous predictions and measurements. The temperature distributions in the substrate for different stand-off distances are predicted.