两层浆搅拌釜内混合过程的新二维单元串联模型

在直径为１８６ｍｍ的立式搅拌釜内,利用热电偶－－温差法测量了两层经组合浆搅拌釜内的液相混合时间,试验中采用的搅拌将有直叶圆盘涡轮和斜叶涡轮（上推式荼吉涡轮ＰＴＵ和下压式斜叶涡轮ＰＴＤ）;根据激光多普勒测速仪对流场的测量结果,提出了一种新的二维单元串联模型,用该模型对两层组合浆搅拌釜内的混合过程进行了模拟,发现模拟值和实验值吻合较好。     

气液搅拌釜中不同因素对混合时间的影响

在液体石蜡中通入氮气的气液搅拌釜中,通过光差法确定特定混合状态和达到该状态的混合时间,研究了多种因素对气液混合时间的影响。进气流量较小时,随进气流量增加,混合时间明显缩短;但当进气流量达一定值时,混合时间变化很小。比较了12个搅拌桨,转速和进气流量均相同时,6叶大圆盘涡轮桨混合时间最短;列出了4种桨型混合时间的长短顺序。转速和进气流量一定时,用4挡板替换3挡板,混合时间略有缩短。     

搅拌釜中自浮颗粒三相体系的混合时间

液相混合时间是搅拌过程中的重要内容。在釜径３８６ｍｍ的搅拌釜内,采用热电偶温差法考察了搅拌桨型、挡板、等操作因素对自浮颗粒三相搅拌混合的液相混合时间的影响。     

多层翼形桨搅拌槽内混合过程的CFD模拟

The mixing process in a stirred tank of 0.476m diameter with single, dual and triple 3-narrow blade hydrofoil CBY impellers was numerically simulated by using computational fluid dynamics （CFD） package FLU-ENT6.1. The multi-reference frame （MRF） and standard k-ε turbulent model were used in the simulation. The shaft power and the mixing time predicted by CFD were in good agreement with the experiment. The effects of tracer feeding and detecting positions on mixing time were investigated. The results are of importance to the optimum design of industrial stirred tank/reactors.     

多层CBY组合桨搅拌槽内混合特性的研究

在直径为０．５ｍ的搅拌釜内,采用酸碱中和法测定了多层桨搅拌过渡区的混合时间,应用电导率法测定了湍流区的混合时间,研究了桨叶安放角,桨径,层间距,搅拌雷诺数,桨型对混合特性的影响规律。     

搅拌釜内气液自浮颗粒三相体系混合的功耗研究

对搅拌釜内气液固（自浮颗粒）三相体系混合的功率消耗进行了测量,研究了搅拌浆组合、档板组合和气体分布器对功耗的影响,对较佳的搅拌浆组合、挡板组合和气体分布器回顾了功耗经验并联式,用于工业放大过程。     

轴流式翼型-透平组合桨在搅拌釜内的流动

<正>搅拌反应器是化工、医药、食品工业中广泛应用的基础设备之一,当搅拌釜内液深与搅拌釜直径相比较大时(通常比值大于1),往往采用双层或多层桨,以保证顶部到底部的循环流动。 透平桨产生的是径向流,形成以桨叶为中心线的上、下2个循环区,桨叶附近剪切速率高,气体分散能力强。翼型桨产生的流型是轴向流,形成全釜循环,混合均匀,剪切温和。为充分利用两者优势,加强全釜混合,剪切适度,特别是在粘稠物系中,可采用组合桨。目前尚未看到对翼型-透平组合桨流动状况的研究,而对于非牛顿流体中的组合桨流动状况则了解     

大功率多层搅拌釜搅拌轴的设计制造

介绍了一种大功率多层搅拌釜的搅拌轴的加工工艺,使得该搅拌器密封处径向摆动和轴下端摆动值较易控制在设计要求范围内。     

三桨叶搅拌釜相同混合时间条件下的CFD模拟及放大研究

搅拌釜的放大主要依靠实验或经验进行,目前已有的各种放大规律由于相似理论的出发点不同,缺乏统一的评价标准.采用CFD技术为统一的放大理论基础,针对4个几何相似的三桨叶搅拌釜,以完全混合所需要的时间T99相同为放大基准,对搅拌釜内的湍流场以及搅拌转速、单位容积消耗功率等随搅拌釜几何放大后的变化规律进行了研究.结果表明,采用CFD技术作为统一的放大理论基础,准确、可靠.     

组合桨聚合釜内非牛顿流体的混合特性

在φ476mm的椭圆底有机玻璃聚合釜中,以羧甲基纤维素-甘油水溶液(前者质量分数为1.3％)为实验物系。利用酸碱中和法测定了9种不同的搅拌桨直径与聚合釜直径比接近于1的组合搅拌桨沿聚合釜轴向及径向的混合特性。结果表明：内外螺带-锚式组合桨的轴向混合最强,但径向混合较差。框板式搅拌桨的轴向混合较内外螺带-锚式组合桨弱,但比改进偏框式桨强,其径向混合较后者弱。改进偏框桨的7种不同组合方式沿径向的混合良好,多数组合桨沿轴向的混合较前2种组合桨弱,更接近于平推流。     

双层翼型桨搅拌槽内流动特性的PIV研究

在直径0.476 m的搅拌槽内,采用粒子图像测速技术对双层三叶CBY翼型桨搅拌槽内的流场进行了研究,考察了层间距、浸没深度和离底高度等参数对流场分布的影响. 结果表明,层间距H2≤0.6T(T为搅拌槽直径)时,槽内可形成整体的轴向循环流动,H2≥0.7T时槽内将产生分区流动现象. 浸没深度对桨叶排出流区域的速度影响很小. 降低下层桨的离底高度能加强下层桨的径向流动,并增大上层桨叶轮区和循环区流体的轴向流动.     

New Turbine Impellers for Viscous Mixing

New open impellers developed for viscous mixing applications were characterized experimentally in terms of power consumption and mixing times, and their performance was compared to that of standard turbines. Their design is based on a nonsymmetry of revolution principle contrary to standard impellers. A color‐discoloration technique based on a fast acid‐base indicator reaction and image analysis were used to evaluate the mixing efficiency. Experimental results show that the segregated, torus‐shaped regions, always observed above and below standard turbine impellers, can be significantly reduced using the new turbine designs generating a well‐balanced axial‐radial flow field.     

Effects of Geometrical Factors on Liquid Mixing in a Gas-Induced Agitated Tank

An agitated tank having two 45° pitched blade downward turbines in series and four thin baffles which were narrower than the conventional ones was studied. At higher impeller speeds, a gas and liquid vortex induces the gas above the liquid surface vertically downward into the turbines, which in turn cuts the gas stream into bubbles which then circulate in the liquid. Consequently gas-induction increases the gas utilization ratio as well as simplifying the ancillary equipment otherwise required to recycle the escaped gas. The relationship between tank geometrical factors and the liquid mixing time was also investigated. The experimental variables investigated were the impeller speed, the baffle width, the turbine diameter, the space between two impellers, the liquid level, and the clearance between the lower turbine and the bottom of the tank. The results showed that all but the clearance between the lower turbine and the bottom of the tank had significant effects on the mixing time under normal gas-induction, revealing results in contrast to the conventional agitated tank. © 1997 SCI.     

Reconciling Electrical Resistance Tomography (ERT) Measurements with a Fluid Mixing Model for Semi‐Batch Operation of a Stirred Vessel

An electrical resistance tomography (ERT) system retrofitted to a 2.3 m³ vessel has been used to image the vessel volume for single feed semi‐batch operation. Images reconstructed from the raw ERT measurements may be represented as time incremented 3‐D iso‐surface representations of the fluid mixing. ERT derived mixing curves have been evaluated against a network of zones (NOZ) mixing model, which is able to compute the time evolving concentration fields. Like the ERT system, the NOZ model is also able to visualise the evolving feed plume and has the power to predict the corresponding time‐wise reaction behaviour in space for a simple A + B → products reaction.     

Unsteady Mixing Characteristics in a Vessel with Forward‐Reverse Rotating Impeller

Usually, mixing is carried out in a vessel with four baffles and a single impeller. In some applications, however, the use of a baffled vessel is not recommended. One of the stirring methods used instead is unsteady agitation with forward‐reverse rotating impellers. The aim of this work was to characterize the agitation characteristics in a baffled and an unbaffled vessel with a turbine impeller. Mixing time and mixing power were evaluated in relation to the presence of baffles and the frequency of forward‐reverse rotation. It was found that the frequency of oscillation does not affect either the mixing time and mixing power values or the drag and added mass coefficients. Power requirements and mixing time were higher compared to the steady mixing conditions in a baffled vessel. The results showed that it is not recommended to use baffles because they have no influence on unsteady mixing.     

多级搅拌塔气液液系统的轴向混合

本文在内径为５４ｍｍ，级数为１６的多级搅拌塔中，研究了空气－水－煤油系统的轴向混合性质。讨论了搅拌转速、水相流速、有机相流速及气相流速对液体连续相和分散相轴向混合的影响。得到了操作范围内描述塔内轴向扩散系数的关联式。对连续水相：Ｅｃ＝０．７４５·Ｎｓ０．５３０·ｕｇ０．４５９·ｕｃ０．６９１·ｕｄ０．３１９对分散有机相：Ｅｄ＝２１．９２·Ｎｓ０．４６５·ｕｇ０．８９８·ｕｃ０．２５８·ｕｄ０．７６２     

Mixing Time in a Short Bubble Column

Mixing time measurements have been carried out in a 0.2m I.D. short bubble column (Hc/D ? 5) with different spargers and for different clear liquid height to diameter (H_C/D) ratios. Superficial gas velocity has been varied in the range of 0.01m/s to 0.1m/s. Effect of bulk fluid viscosity on the mixing time has also been studied. The circulation cell model, with two fitted parameters viz. number of circulation cells, S and the inter‐cell exchange velocity, V_e, has been used to predict and explain the variation in mixing time and the flow pattern in the short bubble column for different types of spargers.