加压釜搅拌槽气液两相流动的数值模拟

利用计算流体力学(CFD)软件Fluent,对某冶炼厂现有搅拌器和优化后搅拌器搅拌槽内的气液两相流动和混合进行了数值模拟,对比了两种搅拌器搅拌槽内的速度分布、局部气含率和搅拌功率。计算结果表明,优化后的搅拌器搅拌混合效果和气体分散优于现有搅拌器,且搅拌功率基本不变。     

气液两相管流流型信号的小波去噪处理

流型信号能够反映气液两相管流的流动特征,它们往往会伴随着各种随机噪声,为此建立了一座气液两相流的综合试验装置,提取气液两相管流的流型信号．采用小波变换对信号样本的进行多尺度分解,利用信号和噪声在不同尺度上的特性把它们区分开来,消除噪声后再对信号进行重构,得到了较好的去噪效果．     

基于LF钢包炉气液两相区的三维Euler模型计算及分析

针对某钢厂85t圆筒型LF钢包炉，建立起了气液两相流三维Euler模型，通过对两相区基本参数气含率和速度分布的分析，得到钢包内气液两相区呈倒锥型结构的结论，很好地验证了全浮力模型理论。     

不同排列双圆柱气液两相绕流数值模拟

在一定的来流速度下,采用有限容积法计算了不同含气率、不同来流速度与双圆柱圆心连线角度情况下,整个流场的变化.夹角选取为α=90°(并列)、60°、45°、30°、0°(串列).结果表明:当α=90°(并列)时,两圆柱后产生稳定的同步反相旋涡脱落.随着夹角的减小,两柱之间产生了强大的排斥力,上游圆柱振动受到抑制,尾涡的长度变短.当夹角α=0°时,上游圆柱涡脱落得到了有效的抑制,没有稳定涡街生成,升力系数的脉动值趋于零;上游圆柱脉动升力系数最大值出现在α=90°,最小值出现在α=0°.研究还发现,上游圆柱的脉动升力系数并不是随着夹角减小而顺次减小;上游圆柱脉动升力系数绝对值随含气率的增大而减小.     

基于湿法冶金过程中气-液两相流体力学特性的CFD模拟

采用E-E与PBM模型耦合,探究不同搅拌速率、通气速率、液体黏度下搅拌釜内气-液两相流体力学特性。重点模拟和讨论不同搅拌速率、通气速率、液体黏度下瞬态气含率、液体速度、气泡直径分布等气-液两相流体力学参数,使密闭搅拌釜内气-液两相流体运动状态可视化,为湿法冶金气-液搅拌过程优化操作条件提供指导。     

RH壁面润湿性对气液两相流行为的影响研究

以某钢厂300 t RH真空精炼炉为原型,建立了相似比为1:1的三维数值模型,研究RH气液两相流在不同壁面润湿条件下行为变化.通过采用多相流(Eulerian)模型进行气液两相流模拟,对不同的壁面润湿条件下的流体行为和流动特性进行分析.结果表明各种提升气体量下,壁面润湿角在60°时循环流量、气相体积分数和浸渍管内液相速...     

320m~3充气机械搅拌式浮选机内气液两相流的数值模拟

随着经济发展对矿产资源需求的不断增长,大型浮选机以其高效率和低能耗优势已成为国际潮流;作为辅助设计和效能评估的重要工具,CFD技术已成为进行大型浮选机研究、设计的关键技术手段之一。本文利用CFD技术针对320 m3充气机械搅拌式浮选机槽内气液两相流进行仿真计算,在确定合适模型的情况下,将得到的气、液流场、液面气液流速、叶轮功耗等在浮选机工业清水试验中较为重要的参数与工业试验所得的数据进行对比。结果表明,所选用的数学模型可以较准确地描述浮选机槽内气液流场,可以为浮选机的设计、改进提供依据。     

Measurements of the internal structure of gas-liquid plumes

Gas injection into liquid metals has been studied extensively with gas injection into water models. While the general features of such flows are appreciated, the structure of the two-phase region has not been well characterized. To improve our understanding of the fundamental transport phenomena in the two-phase region, a combined laser Doppler anemometry (LDA) and electrical probe (EP) technique has been developed to measure the time-averaged and fluctuating liquid velocities, bubble velocities, and void fraction. The primary findings are: (1) The slip velocity of the bubbles is close to the terminal rising velocity of bubbles in stagnant fluids. (2) The intensity of turbulence in the two-phase region is generally higher than 0.5, which is higher than in the single-phase region. (3) The turbulence is not isotropic; it is greater in the vertical direction. The implications for mathematical modeling and process analysis are discussed.     

锌铈液流电池研究进展

能源是经济发展和人们生活的重要物质基础.化石燃料的过度消耗加速了能源危机和环境污染的出现.新能源的利用是解决能源问题和环境问题的必然选择.太阳能、风能和潮汐能等新能源发电具有间歇性的特点,给电网的安全稳定运行带来很大的挑战.储能技术是新能源开发的关键技术.在各种储能技术中,电化学储能日益受到重视.液流电池是一种高效大规模储能系统.锌铈液流电池是已知的单电池电压最高的水溶液电解质电池.文中阐述了锌铈液流电池的工作原理,从正半电池反应、负半电池反应和隔膜3个方面综述了当前的研究进展.指出了锌铈液流电池研究中需重点关注的基础问题.     

Overestimation of a stenosis in the internal carotid artery by duplex sonography caused by an increase in volume flow

In magnetocardiographic (MCG) localization of arrhythmia substrates, a model of the thorax as volume conductor is a crucial component of the calculations. In this study, we investigated different models of the thorax, to determine the most suitable to use in the computations. Our methods and results are as follows. We studied 11 patients with overt Wolff-Parkinson-White syndrome, scheduled for catheter ablation. The MCG registrations were made with a 37-channel "superconducting quantum interference device" system. The underlying equivalent current dipole was computed for the delta-wave. Three models of the thorax were used: the infinite halfspace, a sphere and a box. For anatomical correlation and to define the suitable sphere and box, magnetic resonance images were obtained. As reference we used the position of the tip of the catheter, at successful radio-frequency-ablation, documented by cine-fluoroscopy. Nine patients could be evaluated. The mean errors (range) when using the infinite halfspace, the sphere and the box were 96 (49-125), 21 (5-39), and 36 mm (20-58 mm), respectively (p < 0.0001). In conclusion, the sphere was significantly better suited than the other models tested in this study, but even with this model the accuracy of MCG localization must further improve to be clinically useful. More realistic models of the thorax are probably required to achieve this goal.     

Objective tinnitus caused by an aberrant internal carotid artery

(+)-Norfenfluramine is the main metabolite of the serotoninergic anorectic agent (+)-fenfluramine. Both compounds inhibit 5-HT reuptake and stimulate its release, although they induce release from different pools, with (+)-norfenfluramine acting primarily on the cytoplasmic pool. Moreover, (+)-norfenfluramine was more potent than the parent drug in inducing dopamine release. In order to investigate whether (+)-norfenfluramine induces a Ca2+-dependent vesicular release, like some amphetamine derivatives, in the present study we preloaded synaptosomes with the [3H]neurotransmitter ([3H]5-HT or [3H]dopamine), superfused (washed) them for 47 min in the absence of pargyline and then exposed them to the releasing stimulus. With this protocol, the cytoplasmic pool should be absent and the [3H]neurotransmitter should mainly be stored in synaptic vesicles, where (+)-norfenfluramine should act to induce release. This was confirmed by a significant decrease of (+)-norfenfluramine-induced [3H]5-HT and [3H]dopamine release after reserpine pretreatment. The dose-response curves of (+)-norfenfluramine-induced [3H]5-HT release were superimposable in hippocampus and hypothalamus, and also superimposable on the curve for (+)-fenfluramine-induced [3H]5-HT release; the dopamine releasing potency of (+)-norfenfluramine in the striatum was more than ten times lower. The [3H]5-HT release induced by (+)-norfenfluramine was partly (about 50%) but significantly Ca2+-dependent, and it was also markedly (68%) inhibited by Cd2+, a non-specific blocker of voltage-dependent Ca2+ channels, suggesting that the Ca2+-dependent release is mediated by entry of Ca2+ into the synaptosomes through these channels. The [3H]dopamine release induced by 5 microM (+)-norfenfluramine was completely Ca2+-independent whereas at higher concentrations (10 and 20 microM) it was only slightly (20%) Ca2+-dependent. We have no clear explanation why (+)-norfenfluramine has these different effects on serotoninergic and dopaminergic synaptosomes.     

Injuries of the ureter caused by external force. New viewpoints

Metabotropic receptor subtypes have been proposed based on pharmacological, signal transduction and cDNA sequence data. We assessed potential metabotropic binding site subtypes with in vitro quantitative [3H]glutamate autoradiography in adult rat brains in the presence of saturating concentrations of N-methyl-D-aspartate (NMDA) and (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionate (AMPA). Quisqualate (QUIS) competition curves resolved two differentially distributed binding sites (KIhigh = 17 nM; KIlow = 62 microM). Trans-1-amino-cyclopentane- 1,3-dicarboxylic acid (t-ACPD) and 1S,3R-ACPD displaced [3H]glutamate binding both in the absence and presence of a quisqualate concentration (2.5 microM) that saturates the high affinity sites, suggesting that both sites are linked to metabotropic receptors. We conclude that two metabotropic binding sites with different distributions and pharmacological profiles can be detected with selective [3H]glutamate binding assays.     

棒式文丘里除尘器气液两相流阻力特性

为了掌握棒式文丘里除尘器内气液两相流的阻力特性,基于多相流理论,建立其三维CFD模型,研究分析棒间距、除尘风量和液气比对棒式文丘里除尘器阻力特性的影响,并建立了阻力预测公式以及三者之间的关系式.结果表明：文丘里棒层与下筒体的压力损失随着棒间距的减小和风量的增大呈幂指数关系增大,随着液气比的增大呈近线性增大;上筒体的压力损失与风量呈近平方关系;通过与实验数据对比,关系式最大误差为16.88%,验证了其有效性.     

钢铁制造流程物质流与能量流协同优化研究进展

钢铁企业具有流程长、能耗高、排放量大等特点,钢铁制造流程物质流与能量流的协同优化是实现高层次系统节能的关键.为此,对钢铁制造流程物质流和能量流优化的研究进展与应用进行了综述,在此基础上阐述了钢铁制造流程物质流与能量流协同优化的主要研究方向,即物质流与能量流的相互影响和协同规律研究、考虑能源约束的生产计划编制和物流与能流...     

Theoretical modelling of gas-liquid two-phase flow in a vertical and straight pipe

This paper treats the theoretical analysis to obtain the flow characteristics of gas-liquid two-phase mixtures in a vertical and straight pipe. The system of equations governing the gas-liquid two-phase flow field is based upon the multifluid model. The transitions of the gas flow pattern from bubbly to slug flows as well as from slug to churn flows are introduced into the system of the above governing equations. In order to confirm the validity of the present theoretical model, the flow characteristics calculated on the basis of this model have been compared with experimental data measured by changing the pipe diameter and the submergence ratio. As a result, it has been found that the present theoretical model built up in this investigation gives good fit to the measured data. We believe that the simplicity of this pump can make it possible to transport molten iron/steel between different refining processes. But, we also note that the experiments have been performed on a cold model using an air-water system     

Angina caused by subclavian-coronary steal in patients revascularized with internal mammary artery]

After coronary bypass surgery in the left internal mammary artery, occlusive atherosclerosis in the proximal subclavian artery can produce reverse flow in the mammary artery and myocardial ischemia (coronary-subclavian steal syndrome). This is a rare cause of recurrent myocardial ischemia. We present two patients with postoperative complete obstruction in the proximal subclavian artery and inverse flow in the mammary artery producing severe ischemia in the left anterior descending artery territory. Both patients were treated with subclavian-subclavian bypass, which in one patient was ineffective in producing an adequate anterograde flow in the left internal mammary artery. We review clinical management, diagnostic methods and therapeutic options used in the coronary-subclavian steal syndrome.