共查询到20条相似文献,搜索用时 15 毫秒
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Liangcai Zhong Liying Li Bao Wang Maofang Jiang Lixing Zhu Li Zhang Rongrong Chen 《国际钢铁研究》2006,77(2):103-106
Fluid flow characteristics in a two‐strand slab tundish with Ar bubbling curtain were studied in water modelling experiments. It was found that the Ar bubbling curtain can greatly improve the flow characteristics in the tundish with a weir, a dam and a turbulence inhibitor. It dramatically increased the peak concentration time and plug volume and greatly decreased the dead volume, but hardly influenced the minimum residence time. Therefore, the fluid flow characteristics in a tundish with Ar bubbling curtain were favourable to the flotation and separation of inclusions from molten steel. The flow characteristics with low gas flow rate and short distance of the Ar bubbling curtain from the tundish outlet were better than those with high gas flow rate and large distance of the curtain from the outlet. 相似文献
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《钢铁冶炼》2013,40(6):436-440
AbstractFluid flow characteristics in a two strand slab continuous casting tundish with different configurations of argon gas bubbling curtain (GBC) were investigated in physical modelling experiments. It was found from this research that the GBC with a small flow rate acted as a gas dam and could greatly improve the flow characteristics in the tundish. It increased dramatically the peak concentration time and plug flow volume, decreased greatly the dead volume, created surface directed flow and eliminated short circuiting. Therefore, the fluid flow characteristics in a tundish with GBC were favourable to the floatation and separation of inclusions from molten steel. The flow characteristics with low gas flow rate and short distance of the bubbling curtain from the tundish outlet were better than those with high gas flow rate and large distance of the curtain to the outlet. The optimal configuration for the improvement in fluid flow characteristics was turbulence inhibitor (TI)–weir–dam–GBC (TI–W–D–GBC), followed by TI–channel weir (CW)–GBC, TI–W–GBC and TI–GBC. 相似文献
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Lino García‐Demedices Rodolfo D. Morales Simon Lpez‐Ramírez Jos de J. Barreto‐Sandoval Jorge Palafox‐Ramos Manuela Díaz‐Cruz 《国际钢铁研究》2001,72(9):346-353
Simple changes on tundish geometry may lead to significant improvements of transport phenomena of liquid steel in tundishes. In the present case steel flow in a six‐strand billet trough type tundish is mathematically simulated. Numerical results indicate the existence of a high fluid turbulence in the pouring zone and recirculating flows. Steel temperatures in the strands are also different, which from practice it would mean different qualities of billet among the strands. A simple change of design by widening the pouring box improves all the steel flow characteristics. First the turbulence in the pouring box is decreased, the recirculating flows are eliminated and steel temperatures in the six strands become closer to each other. Using a computational technique known as volume of fluid, surface topography of bath including the covering slag was simulated for both types of tundishes. These simulations predicted an open eye of the slag layer for the first tundish while in the second this phenomena was avoided. Thus, it was demonstrated the original hypothesis that small changes in tundish design may lead to a more controlled steel flow. 相似文献
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Various forms of plumes have been identified following the injection of air at different rates through a porous plug into
water contained in a ladle-shaped vessel. Discrete bubbles form at the plug and rise uniformly through the column of liquid
at gas flow rates up to 14 cm3/s cm2 of plug surface; at higher flow rates, groups of bubbles increasingly coalesce into larger gas pockets, and beyond about
40 cm3/s cm2, the gas globes are large enough to cover the entire plug surface before detachment and gradual disintegration as they rise
through the body of liquid. The gas fraction, as well as bubble frequency, bubble velocity, and bubble size, have been measured
in the various dispersion regimes by means of an electroresistivity probe. The radial distributions of gas fraction and bubble
frequency are approximately bell-shaped about the axis of flow, and the reduced values are close to Gaussian functions of
the reduced radial distance from the axis. The gas fraction along the axis has been correlated to the reduced height of the
plume; it increases with decreasing distance above the plug and with increasing gas flow rate. The axial bubble frequency
shows a decrease in the vicinity of the plug with the onset of bubble coalescence, but the values of the frequencies at all
gas injection rates converge to about 12 s−1 toward the surface of the bath. The mean bubble velocity increases with increasing flow rate but drops once coalescence is
fully established. Conversely, there is a sudden increase in the mean bubble diameter with the onset of coalescence. The axial
and radial components of the velocity of the liquid surrounding the plume have been measured by means of a Laser-Doppler Velocimeter
(LDV), and the results show that the circulation patterns are identical, irrespective of the dispersion regime. The axial
flow which is upward in the vicinity of the plume decreases in magnitude with increasing radial distance, ultimately reversing
to an in-creasing downward flow beyond a certain distance from the plug axis. Similarly, the radial flow which is outward
from the plume near the liquid surface decreases steadily with depth and eventually reverses to an inward flow at a depth
independent of the gas injection rate. The profiles of the axial velocities are almost sigmoidal, except in the coalescence
regime, where the effect of turbulence is profound at the upper liquid layers. The radial liquid velocities are generally
small relative to the axial components, only about one-fifth as large, considering the maximum average values. 相似文献
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A. Aguilar-Corona Professor Rodolfo D. Morales Professor Manuela Díaz-Cruz Jorge Palafox-Ramos Dr.-Ing. Researcher H. Rodríguez-Hernández 《国际钢铁研究》2002,73(10):438-444
The effects of off-centered ladle streams on fluid flow of liquid steel in a two-strand slab tundish were studied using water modelling techniques and particle image velocimetry (PIV) measurements. Fluid flow in an off-centered ladle stream was compared with a centered ladle stream. In a centered position the proposed arrangement (turbulence inhibitor plus dams) yields higher fractions of plug flow than the current arrangement (baffles). This effect is stronger at the high casting rate. An off-centered position increases dead volumes at a low casting rate of 1.7 t/min. At the high casting rate of 3.8 t/min, effects of the off-centered position are decreased although the TI-D arrangement always renders better flow characteristics. Velocity fields determined with PIV measurements, demonstrated that the TI-D arrangements provide the fluid with a plug flow characteristic. 相似文献
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在相似理论的基础上,通过水力学模拟对两流板坯连铸中间包3种不同气幕挡墙形式下的包内流场进行研究。实验结果表明:在同一吹气量(28L/h)时,气幕挡墙置于中间包端部(方案一),在气幕的两侧形成两个方向相反的回流区域,延长了钢液的平均停留时间,采用该方案时中间包内死区比例为18.5%;气幕挡墙置于中间包墙坝之间(方案二),也形成了两个较大的回流区,增加了钢液间的混合和夹杂物的去除,中间包内死区最小为17.4%,为三种方案之最优;气幕挡墙置于中间包挡墙之前(方案三),气幕挡墙并未形成有效的气幕,中间包内部流体未得到充分混匀,出现27.5%的较大的死区。 相似文献
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S. Chatterjee 《钢铁冶炼》2017,44(6):403-412
A numerical model based on computational fluid dynamics was used to simulate the effect of non-isothermal conditions on melt flows in a multi-strand billet caster tundish. To start with, water was used as the operating fluid in a one-third scale tundish to calculate the fluid flow and temperature fields under isothermal and non-isothermal conditions. The model was then extended to the full-scale tundish with molten steel as the operating liquid in order to simulate the conditions in a real plant. It was observed that using step inputs of 10° and 23° for water and steel cases, respectively, changed the fluid flow patterns significantly, more so at locations far from the inlet, due to stronger buoyancy-driven natural convective flows. The temperature distribution and inclusion trajectories within the tundish were also affected due to the presence of non-isothermal conditions. 相似文献
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Mathematical simulation of fluid dynamics during steel draining operations from a ladle 总被引:2,自引:0,他引:2
O. Davila L. Garcia-Demedices R. D. Morales 《Metallurgical and Materials Transactions B》2006,37(1):71-87
Fluid flow dynamics during ladle drainage operations of steel under isothermal and nonisothermal conditions has been studied
using the turbulence shear stress transport k-ε model (SST k-ω) and the multiphase volume of fluid (VOF) model. At high bath levels, the angular velocity of the melt, close to the ladle
nozzle, is small rotating anticlockwise and intense vertical-recirculating flows are developed in most of the liquid volume
due to descending steel streams along the ladle vertical wall. These streams ascend further downstream driven by buoyancy
forces. At low bath levels, the melt, which is close to the nozzle, rotates clockwise with higher velocities whose magnitudes
are higher for shorter ladle standstill times. These velocities are responsible for the formation and development of a vortex
on the bath free surface, which entrains slag into the nozzle by shear-stress mechanisms at the metal-slag interface. The
critical bath level or bath height for this phenomenon is 0.35 m (in this particular ladle design) for a ladle standstill
time of 15 minutes and decreases with longer ladle standstill times. At these steps, the vertical-recirculating flows are
substituted by complex horizontal-rotating flows in most of the liquid volume. Under isothermal conditions, the critical bath
level for vortex formation on the melt free surface is 0.20 m, which agrees very well with that determined with a 1/3 scale
water model of 0.073 m. It is concluded that buoyancy forces, originated by thermal gradients, as the ladle cools, are responsible
for increasing the critical bath level for vortex formation. Understanding vortex mechanisms will be useful to design simple
and efficient devices to break down the vortex flow during steel draining even at very low metal residues in the ladle. 相似文献
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通过水模拟实验,研究了气幕挡墙位置、气体流量及采用双透气砖对中间包流场的影响;认为采用气幕挡墙可有效延长钢水在中包的平均停留时间,降低死区,混匀钢水;并提出工业性试验的可行性建议。 相似文献
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The present study focuses on the fluid dynamics of vortex formation in tundish operations using a physical water analogue model and Particle Image Velocimetry (PIV) measurements. The aim is to get fundamental knowledge of the nature of vortex formation that clearly represents this flow phenomenon. The results indicate that vortex formation is directly related to the highly turbulent flows present in the tundish. Great changes of velocity fields during short times and large distances between the upper edge of the dam and the free surface of the bath enhance the formation of vortex flows. Therefore, increasing tundish capacity does not guarantee steel cleanliness through long residence times if the dam height is not adjusted to the new level of liquid in the tundish. 相似文献
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Physical and mathematical determination of the influence of input temperature changes on the molten steel flow characteristics in slab tundishes 总被引:1,自引:0,他引:1
S. López-Ramírez J. De Barreto P. Vite-Martínez J. A. Romero Serrano C. Duran-Valencia 《Metallurgical and Materials Transactions B》2004,35(5):957-966
Transient fluid flow behavior in a tundish with two different arrangements, a bare tundish and a tundish using flow control
devices, was studied using physical modeling and a mathematical model. The study places special emphasis on buoyancy effects,
particularly transient buoyancy effects due to step change in inlet temperature. For the bare tundish case, the inertial forces
are strongly dominant, while in the arrangement using flow control devices, tundish with turbulence inhibitor and low dams,
the buoyancy forces are dominant. The results were compared to those representing the real behavior, considering temperature
variations, for each tundish arrangement. This comparison made possible the determination of the probable implicit error that
could be present in the estimation of the fluid flow characteristic behavior used for the design of the tundish geometry and
flow control devices when the temperature variations are not considered. 相似文献
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通过几何相似比0.29:1的水模型试验了湍流抑制器+挡墙+挡坝和湍流抑制器+挡墙+过滤器两种控流装置的钢液流动,研究了通道式过滤器对58t中间包钢液流场的影响。结果表明,原中间包(湍流抑制器+挡墙+挡坝)活塞区体积小,死区体积高达29.53%,优化中间包加入过滤器后(湍流抑制器+挡墙+过滤器)短路流基本消失,钢液的实际平均停留时间延长,死区体积由29.53%减小至13.52%。50t中间包,230mm×1100mm连铸板坯,拉速1.25~1.30m/min工业生产结果表明,使用过滤器后,中间包浇注区的夹杂物尺寸明显小于冲击区,中间包浇注区T[O]由原86×10-6降至30×10-6,连铸坯大多数夹杂物尺寸≤10μm,没有发现≥30μm夹杂物。 相似文献
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Saikat Chatterjee Amjad Asad Christoph Kratzsch Rüdiger Schwarze Kinnor Chattopadhyay 《Metallurgical and Materials Transactions B》2017,48(1):17-21
Tracer dispersion experiments were carried out in a multi-strand tundish by injecting 1 (N) NaCl solution into water. The variation of dimensionless concentration–time curves known as C-curves and mixing times with different gas flow rates were studied. The proportions of dead, mixed, and dispersed plug volumes were calculated using the ‘modified mixed model.’ The observations were explained by analyzing the behavior of the bubble plume, incoming jet velocity, and turbulent kinetic energy within the tundish. 相似文献
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