薄板坯连铸浸入式水口结构数值模拟

使用有限元计算方法开展薄板坯连铸浸入式水口流场的研究 ,分别对水口不同浸入深度的流场分布、水口出口不同角度的流场分布进行计算。结果发现 :水口的浸入深度在 30 0mm时较为合理 ;水口的出口角度以R1 5、60°、45°为宜     

采用水模拟进行浸入式水口到结晶器的钢水流分析

采用水模拟和计算机模拟的流动分析,研究了浸入式水口流出孔及面内底部形状对钢水流的影响,并对两种方法的分析结果进行了比较。     

阶梯式浸入式水口的水模拟试验

通过将水口内壁改成台阶形状,既消除了逆流现象又使出钢流速均匀,同时还防止了氧化铝附着。     

宽板坯连铸结晶器流场的水模拟研究

采用水模拟试验,研究了宽板坯用浸入式水口的出口面积比(分别为1.2、1.5、1.8、2.1)和出口倾角(分别为0°、15°、30°)对结晶器内流场和表面波动的影响.结果表明:(1)水口出口面积比对射流在结晶器窄壁的冲击强弱影响显著,随出口面积比变大,对窄壁的冲击逐渐减弱;液面波动随水口出口面积比变大而减弱.(2)水口出口倾角对上回流强弱影响显著,随水口出口倾角变大,上回流主涡旋强度逐渐减弱,当出口倾角为向下30°时,上回流大涡旋消失;液面波动随水口倾角变大而显著减弱.(3)综合分析后认为,水口出口面积比为1.8,出口倾角为0°时,液面较活跃,且下涡心位置较高,有利于钢液中夹杂物上浮及凝固壳的生长.     

薄板坯连铸用浸入式水口的性能与使用

针对薄板坯连铸用浸入式水口的使用条件,选择了水口不同部位的材质。以板状刚玉、氧化铝粉、锆莫来石、电熔稳定氧化锆、电熔镁砂、天然鳞片状石墨等为原料制备了浸入式水口,重点研究水口本体铝碳材料的抗氧化性能和渣线锆碳材料的抗侵蚀性能,并模拟现场使用条件进行了烘烤试验。结果表明:所研制的水口材料性能完全满足使用要求,烘烤时无氧化和剥落;在薄板坯实际连铸生产条件下,所研制的浸入式水口稳定地实现了24炉连浇,为相关的浸入式水口研究提供了良好的基础。     

MOGUL型浸入式水口

为防止钢水在浸入式水口中的再次氧化，研制开发了一种新型的被称之为MOGUL的内衬结构，并用水模型进行了模拟试验。通过流速分布、流型特性等分析，指出新型浸入式水口(SEN)能有效抑制水口和结晶器内发生的钢水偏流现象，改善了钢水质量。     

连铸用浸入式水口的传热模拟

1 前言 连铸用浸入式水口在浇注钢水时,由于快速流过其内孔的钢水温度达1550℃左右,因此水口内外面之间的温差很大,随之会产生热应力,有时会因热剥落而发生裂纹。 以往,作为其措施,一般多是在水口外表面贴绝热材料,以此来努力提高材质的耐热震性,降低因预热水口而产生的ΔT,即降低发     

防止浸入式水口的热损失

连铸中，结晶器内弯液面的温度对稳定操作和提高铸坯质量至关重要，为此开发了低导热性铝碳料，无碳内管料和无纤维绝热包覆料，将这些方法组合起来使用，可以将结晶器的热损失控制在最小限度内。     

90°弯管内湍流流动的数值模拟

进行了90°弯管内湍流流动的数值模拟实验。结果表明,切向速度在开始旋转阶段内侧的速度增大、压力减小,外侧速度降低、压力增大;当转过60°截面后,外侧的速度增大、压力减小,内侧速度降低、压力增大。弯管内流体旋转产生的离心力导致压力分布的变化,使得弯管内流体产生垂直于主流切向速度的轴向速度和径向速度,形成了二次流。90°弯管流场是主流切向速度与二次流的叠加,呈现出复杂的三维流动特性。     

Numerical simulation of the flow field in the mixing section of a screw extruder by the lattice Boltzmann model

The single-screw extruder is commonly used in polymer processing where the performance of the mixing section is significant in determining the quality of the final product. It is therefore of great interest to simulate the flow field in a single-screw extruder. In this paper the simulation is performed using the lattice Botlzmann model giving a fast and efficient numerical technique. The solution is compared to a finite difference and lattice gas simulation and found to give more accurate results.     

单流中间包气幕挡墙物理模拟研究

通过在实验室的物理模拟,研究透气砖底吹氩技术对中间包内钢液流动和夹杂物去除行为的影响。结合中间包内的停留时间曲线(RTD曲线)、平均停留时间及死区、活塞流体积分数,研究不同位置的透气砖对钢液流动特性的影响,并与不安装透气砖进行对比。结果表明,中间包底吹入气体后,能够有效改善钢液的流动状态,延长钢液的平均停留时间,并能延长响应时间、降低死区体积。当多孔导流隔墙距离中间包上沿600mm、气幕挡墙距多孔导流隔墙500mm时位置最优,平均停留时间最长,死区体积最小。     

Tuning the water permeability of ultra-high molecular weight polyethylene microporous membrane by molecular self-assembly and flow field

We have systematically studied phase separation behavior in ultra-high molecular weight polyethylene/liquid paraffin/dibenzylidene sorbitol (UHMWPE/LP/DBS) ternary blends. The aim of this paper is to investigate the combined effect of DBS and flow field on the structure and water permeability of UHMWPE microporous membrane. The experimental results show that DBS molecules self-assemble into fibrils firstly during cooling and the blends exhibit a gel-like state before liquid–liquid phase transition. The relaxation time of DBS fibrils is quite long, which shows a great sensitivity to flow field as compared to UHMWPE chain. UHMWPE microporous membrane was prepared via thermally induced phase separation method. DBS fibrils, as in situ formed nucleating agent, decrease the pore size and water permeability and enhance mechanical properties of membrane remarkably. Shear flow can result in alignment of DBS fibrils, which facilitates the nucleation of UHMWPE and induces the lamellae aligned perpendicular to flow direction. This feature was used to design thermal and mechanical histories and obtained oriented UHMWPE microporous membrane. In comparison to the isotropic UHMWPE microporous membrane, the oriented UHMWPE microporous membrane provides low tortuous paths across the membrane and produces high water permeability.     

组织工程多孔支架微管内流场数值模拟

骨支架内部微管结构对营养液和细胞在其内部的流动有着非常重要的影响。利用流体计算软件Fluent对不同尺寸的人工骨微管结构内部营养液和细胞的流动状况进行了数值模拟,得到了不同几何结构骨支架内部流场的速度和压力分布图。结果表明,从进口到出口,主管道内流体流速随管道的深入不断减小。上端浮克曼管中流体流速比下端浮克曼管中流体流速高,但是比同一高度主管道内流体流速低。哈佛氏管与第一行浮克曼管交叉处下端的哈佛氏管内存在流动缓慢区,第三行浮克曼管与哈佛氏管交叉处开始,流体速度不断增大。随浮克曼管长度的增加,上端哈佛氏管中流体流动的缓慢区减小;随浮克曼管直径的增加,浮克曼管中的流速有所增加,并且各微管中流体的流速更为均匀;随浮克曼管与主管道夹角的增加,骨支架各微管内流体流速更加均匀,利于细胞和营养液在各管道的输运。本数值模拟范围内,最佳骨支架结构参数为浮克曼管长度3mm,直径0.6mm,浮克曼管与主管道夹角90°。     

FST高效塔板传质元件内气相流场的数值模拟

FST高效塔板是一种喷射型塔板,同鼓泡型塔板相比,具有高通量、低压降等特点。塔板传质元件的结构会很大的影响塔板的传质效率和压降,为了优化塔板结构设计,提升塔板性能,有必要研究不同结构传质元件的效果。本文使用FLUENT软件对FST高效塔板传质元件开展数值模拟研究,得到传质元件内部气相流场,对比了3种结构传质元件内部气相流场的分布情况,考察了除雾叶片、旋流叶片径向角对气相流场的影响。结果显示除雾叶片会增强传质元件的除雾效果,降低塔板的雾沫夹带,但也会带来额外的塔压降。旋流叶片径向角会增强气相旋流强度,强化传质效果,但是也会带来压降过大、回流过大的问题。为优化设计塔板传质元件,应综合考虑各结构因素的影响,合理平衡塔板压降与传质效果、除雾效果。     

变截面导流筒换热器入口流场均化性能数值仿真

采用变截面导流筒真实三维实体模型,通过数值模拟的方法,以流体流动均匀性和压降作为综合衡量依据,研究了变截面导流筒装置中关键结构参数的变化对其内部流体流动均匀性和流体流动阻力的影响规律,得出了导流筒的结构参数L,H,θ与壳程进口处流体流动状况的对应关系,证实了在适当范围内调整上述结构参数,不仅可以提高壳程进口处流体流动均匀性,而且可以有效降低壳程流体的压力损失。从导流筒换热器的流体流动均匀性和壳程压降角度出发,推荐L,θ,H的取值范围分别是:L=50~70 mm,θ=7°~12.5°,H=50~100 mm。研究结果为变截面导流筒换热器优化设计提供了参考依据。     

地下水曝气过程中空气流场的数学模拟

地下水曝气（AS）过程中空气流场的数学模拟是现场过程研究的必要手段。利用饱和度与相对渗透率、毛细压力间的关系建立了AS二维非稳态流场的数学模型,用有限元法模拟了复杂流场非稳态二维气相饱和度场、速度场和稳态压力场分布,结果显示气相饱和度随着曝气时间和距曝气井位置的不同而变化。在曝气5 h左右,流场区域稳定。由饱和度的分布确定了空气在地下水中流型为下部U形,上部水平。在本模拟条件下,单井AS的影响区半径为9 m,若修复大面积污染的地下水,宜采用多井曝气的方式,增大其影响区半径。     

轴向流固定床内流场的数值模拟与实验验证

The computational fluid dynamics model with porosity and drag coefficient was used to describe fluid flow in an axial flow fixed bed according to the characteristics of fluid flow in the fixed-bed of the reactor. The commercial computational fluid dynamics (CFD) code CFX was used to simulate the flow field in the axial flow fixed bed. The simulation predictions are in good agreement with experimental results of a large cold model. The influence of gas distributor on the flow field in the axial flow fixed bed was studied. A suitable gas distributor was used to attain less than 0.06 kPa radial pressure difference and less than 5.2% radial velocity difference in fixed bed.     

Influence of flow field on sedimentation efficiency in a circular settling tank with peripheral inflow and central effluent

The paper presents an experimental study of suspension flow patterns and velocity field inside a circular settling tank with continuous operation. Research was focused on the impact of a specific flow pattern on the sedimentation efficiency of the prototype settling tank. The latter differed from a common circular settling tank in that it was peripherally fed and had the central draw-off. Experiment was carried out on a settling tank section made of plexiglass and represented a radial slice of a prototype settling tank. The flow field and local suspension concentration was determined by computer-aided visualization. Sedimentation efficiency was assessed relatively by comparison of the amount of settled particles (sludge height measurements) between different types of flow in a certain time period of the settling tank operation. Results showed that there were two types of flow in the settling tank that were initiated by a horizontal or vertical inflow from the distribution ring. The type of inflow (horizontal or vertical) was a function of the suspension height in the settling tank. Significant differences in sedimentation efficiency were observed between both types of flow, particularly at lower inlet suspension concentrations. Horizontal inflow proved to be less efficient in terms of settling.