Heat-loss calculation in ladle treatment of steel

A mathematical model permits calculation of the heat losses and temperature variation of liquid steel. The rates of variation in the heat losses and the integral mean temperature of the liquid steel are physically interpreted. A semiempirical formula that performs well in practice is used for the emissivity of slagmetal melt during discharge from a converter. Good agreement is found between the calculated and actual temperature values of the steel in a casting ladle for a continuous-casting machine.     

On Effective viscosity models for gas-stirred ladle systems

Metallurgical and Materials Transactions B -     

钢包浇注过程的数学物理模拟

采用CFD商用软件FLUENT,选取VOF气-液两相流模型和标准k-ε湍流模型对60t钢包浇注过程进行了数值模拟和物理模拟,利用水口流量和液面高度随时间的变化曲线分析了浇注过程中旋涡的产生及变化规律,得到了产生旋涡时自由液面的速度场,并与水模拟实验结果进行了比较.研究结果表明,水口直径及其水口位置对旋涡影响的数值计算结...     

炼钢厂钢包的传热数模研究

研究钢包热循环过程中各个阶段的传热数学模型,分析钢包装钢、静置传运、吹氩和预热烘烤阶段的钢水传热现象,完成了钢包热循环的数值模拟,为合理制定钢包温度制度提供了一定的依据。     

The modeling of pool profiles,temperature profiles and velocity fields in ESR systems

Through the simultaneous statement of Maxwell’s equations, the turbulent Navier-Stokes equations and the differential thermal energy balance equations a mathematical model has been developed to represent the pool profiles, the velocity fields and the temperature profiles in an ESR system. The major advance over earlier modeling efforts is the fact that the model is capable of predicting the pool profiles from first principles. The theoretically predicted pool profiles and temperature fields were found to be in reasonable agreement with experimental measurements reported by Mellberg for a laboratory scale system. The model is used to investigate the interdependence of key process parameters, with the power input, fill ratio, amount of slag used and the position of the electrode as the independent variables and the casting rate, pool depth, velocity and temperature fields as the dependent variables.     

Numerical computation of flow phenomena in gas-stirred ladle systems

Quasi-single-phase mathematical models as applied to the ladle hydrodynamics have been analysed rigorously. It is shown that choice of convergence criteria, nodal configuration and differencing schemes all influence the computed results significantly and consequently, results independent of these numerical parameters must first be established to draw any useful conclusion. Several quasi-single-phase computational procedures reported in the literature to study the gas-injection-induced flow phenomena have been critically examined. To this end, experimentally measured bulk flow-fields, plume-rise velocity and gas voidages have been compared with those predicted numerically. Such comparisons indicate that the bottom injection phenomena (viz., bulk flow, plume-rise velocity, and gas volume fraction within the plume etc.) can be adequately represented by assuming bubble slippage and considering a constant rise velocity in the two-phase region in the numerical solution scheme.     

Approximate calculation of homogenization of liquid steel in a ladle with induction stirring

Derivation of formulae for the calculation of the homogenization in a stirred melt after addition of alloying elements, based partly on the diffusion equation and partly on the tank model. Comparison between calculated and experimental results. Derivation also of a formula for the calculation of the temperature differences in a stirred melt during local heating.     

Flow pattern velocity and turbulence energy measurements and predictions in a water model of an argon-stirred ladle

Experiments were carried out using a simplified water model of an argon-stirred ladle system. The flow patterns were determined by a flow visualization technique and the velocity and turbulence energy fields were quantitatively measured using hot-film anemometry. The latter quantities were predicted by solving the turbulent Navier-Stokes equations using Spalding’sk-W model for the turbulence viscosity. There is semiquantitative agreement between predictions and measurements. Mixing lengths also were computed. This agreement between measurements and predictions provides further evidence that modeling is a promising approach for the study of recirculating turbulent flows in steel processing operations. J. SZEKELY, formerly of the State University of New York at Buffalo.     

Experimental studies on the flow velocity of molten metals in a ladle model at centric gas blowing

Experimental measurements of the flow velocity were carried out with liquid Wood's metal in a ladle-shaped vessel with an inner diameter of 40 cm at centric gas blowing. By means of permanent magnet probes the liquid flow field was measured under various blowing conditions. The results show that a circulating flow field is established in the vessel. In the bubble plume zone an upwardly directed liquid flow is formed. The radial distribution of the flow velocity in this zone follows a Gaussian function. The axial flow velocity increases with growing gas flow rate and is nearly constant in vertical direction. The width of the upward flow becomes larger with increasing distance from the nozzle and its dependence from the gas flow rate is not considerable. At centric gas blowing the liquid in the upper part of the bath streams quickly, whereas in the lower part so-called “dead zones” with very low flow velocity are present. Besides the time-averaged value of the flow velocity, the turbulent behaviours of the liquid flow such as fluctuation velocity, the turbulent kinetic energy and its dissipation rate were investigated on the basis of measured data. It was found that the liquid flow is turbulent particularly in the region of bubble plume and of bath surface. The radial profiles of these parameters can also be described by a Gaussian function. Only a small part of the gas stirring energy is changed into the kinetic energy of the directed liquid flow. Most of the stirring energy is already dissipated in the bubble plume zone.     

新型钢包整体温度场和应力场三维数值模拟

针对新型300t钢包,采用三维有限元数值模拟的方法研究了包壳的整体温度场分布。重点研究了包壳外表面高度方向、桶体与包底连接环焊缝处的温度分布以及钢包一些辅助结构对包壳温度场的影响,从而掌握钢包包壳温度场的分布规律,为新型钢包的日常维护以及如何延长钢包的使用寿命等方面的工作提供一定的依据。     

Spatio-temporal subthreshold receptive fields in the vibrissa representation of rat primary somatosensory cortex

Spatio-temporal subthreshold receptive fields in the vibrissa representation of rat primary somatosensory cortex. J. Neurophysiol. 80: 2882-2892, 1998. Whole cell recordings of synaptic responses evoked by deflection of individual vibrissa were obtained from neurons within adult rat primary somatosensory cortex. To define the spatial and temporal properties of subthreshold receptive fields, the spread, amplitude, latency to onset, rise time to half peak amplitude, and the balance of excitation and inhibition of subthreshold input were quantified. The convergence of information onto single neurons was found to be extensive: inputs were consistently evoked by vibrissa one- and two-away from the vibrissa that evoked the largest response (the "primary vibrissa"). Latency to onset, rise time, and the incidence and strength of inhibitory postsynaptic potentials (IPSPs) varied as a function of position within the receptive field and the strength of evoked excitatory input. Nonprimary vibrissae evoked smaller amplitude subthreshold responses [primary vibrissa, 9.1 +/- 0.84 (SE) mV, n = 14; 1-away, 5. 1 +/- 0.5 mV, n = 38; 2-away, 3.7 +/- 0.59 mV, n = 22; 3-away, 1.3 +/- 0.70 mV, n = 8] with longer latencies (primary vibrissa, 10.8 +/- 0.80 ms; 1-away, 15.0 +/- 1.2 ms; 2-away, 15.7 +/- 2.0 ms). Rise times were significantly faster for inputs that could evoke action potential responses (suprathreshold, 4.1 +/- 1.3 ms, n = 8; subthreshold, 12.4 +/- 1.5 ms, n = 61). In a subset of cells, sensory evoked IPSPs were examined by deflecting vibrissa during injection of hyperpolarizing and depolarizing current. The strongest IPSPs were evoked by the primary vibrissa (n = 5/5), but smaller IPSPs also were evoked by nonprimary vibrissae (n = 8/13). Inhibition peaked by 10-20 ms after the onset of the fastest excitatory input to the cortex. This pattern of inhibitory activity led to a functional reversal of the center of the receptive field and to suppression of later-arriving and slower-rising nonprimary inputs. Together, these data demonstrate that subthreshold receptive fields are on average large, and the spatio-temporal dynamics of these receptive fields vary as a function of position within the receptive field and strength of excitatory input. These findings constrain models of suprathreshold receptive field generation, multivibrissa interactions, and cortical plasticity.     

The computation of the velocity fields in mechanically agitated melts for turbulent and non-newtonian regimes

A mathematical model is developed to describe the behavior of melts, agitated by a flat blade impeller, mounted on a rotating shaft. The model was verified by testing against experimental results, obtained using water, where the flow was turbulent. However, the main objective of the work was to describe the velocity fields produced in melt-solid slurries, which are non Newtonian. By using a power-law expression for the viscosity, it was found that these systems can be adequately agitated using mechanical stirring. This is in contrast to previously published results, which indicate that by using conventional electromagnetic stirring arrangements, it would be difficult to agitate melt-solid slurries, particularly at high solid loading levels.     

ANSYS数值计算在紫金山金铜矿矿柱稳定性分析中的应用

主要阐述了ANSYS数值模拟方法在紫金山金铜矿采空区稳定性分析的过程,通过对ANSYS分析结果进行分析,客观地评价了紫金山金铜矿露天地下联合开采过程的采空区围岩稳定性。