微通道内非牛顿流体中液滴生成机理研究进展

微流体技术良好的可控性为制备均一可控的微液滴提供了新的途径,而非牛顿流体因广泛的应用而受到关注。综述了近年来剪切变稀和黏弹性两类典型非牛顿流体中液滴生成机理的研究进展。围绕流动聚焦型和T型微通道两种典型微通道构型,介绍了非牛顿流体分别作为分散相和连续相时液滴生成过程的界面演化动力学,并与牛顿流体液滴生成过程进行了对比,分析了剪切变稀特性和弹性对主液滴和卫星液滴生成的影响。展望了非牛顿流体液滴生成过程待解决的关键科学问题,为进一步的模拟和实验研究提供了借鉴和参考。     

SPH方法在剪切流液滴运动规律研究中的应用

阐述了SPH(Smoothed Particle Hydrodynamics)方法的理论基础和计算方法,应用该方法编写程序计算了液滴在剪切流中的运动规律。通过激波和Poiseuille流动这两个验证算例的计算发现,SPH方法能很好地应用于流体运动规律的计算模拟。另外,还对不同的核函数的计算结果进行了比较,分析了影响计算精度的因素,在此基础上,计算模拟了剪切流中单液滴的运动行为,包括变形、破裂行为。     

剪切变稀流体中液滴运动的研究

采用VOF方法,基于非牛顿流体的流变模型对剪切变稀流体中液滴的运动进行数值模拟.结果发现剪切变稀流体中液滴的上升较稳定,上升速度前期增长较快,后期趋于平缓,轨迹呈直线型;单液滴初始半径r越大,上升过程中产生的形变越明显;溶液的稠度指数k越大,液滴上升的速度v越小;幂律指数n越大,液滴上升的速度v越大,k的作用效果比n效...     

简单剪切橡胶件断裂的有限元分析

通过有限元分析方法模拟简单剪切橡胶件粘结处裂纹扩展时撕裂能与裂纹尺寸的关系。在小裂纹情况下，撕裂能强烈依赖于裂纹尺寸；在裂纹尺寸较大时，撕裂能为常值，与裂纹尺寸无关，有限元解与分析解吻合很好。并用有限元分析结果解释了一个实际产品——卡车用橡胶垫在疲劳实验过程中裂纹扩展的情况。     

流动聚焦微通道内牛顿微液滴在幂律剪切致稀流体中的生成研究

采用开源CFD软件OpenFOAM中的interFoam求解器对流动聚焦微通道内微液滴的形成过程进行了数值模拟。通过与文献中的实验数据进行对比,验证了VOF模型和幂律非牛顿流体模型的准确性。并以此为基础模拟了幂律剪切致稀流体中牛顿微液滴的形成过程,研究了幂律流体的幂律指数n和稠度系数K对微液滴生成的影响。研究表明,在滴状和挤压状流型中,离散线颈部宽度与周期内剩余时间呈幂律关系;离散线长度在坍塌阶段呈现线性缓慢增长,在夹断阶段呈现近似指数迅速增长的趋势。随着n和K的增大,液滴的尺寸逐渐减小,而生成频率则逐渐增大,且n的变化比K的变化对其产生的影响更明显。     

纳米流体液滴凝固过程中的特征变形

为了研究胶体颗粒在液滴凝固中的作用,实验制备了不同浓度、颗粒性质的纳米流体溶液,基于低温台装置,文中实验观察到的纳米流体液滴的凝固形状不再带有尖端,而是在顶部形成了一个平台结构,并且该平台的面积随着纳米颗粒浓度的增加而变大.文中提出了一个简单的物理模型,并通过Hele-Shaw装置对凝固过程观察分析,将平台的形成归因于...     

超疏水表面液滴蒸发内部流体流动与传热分析

基于椭球模型,模拟了超疏水表面上固着纯水液滴的蒸发过程,探究了蒸发过程中液滴外形、体积、接触角、表面温度和蒸发速率的变化,以及液滴内部温度和流线的分布情况。结果表明:液滴蒸发过程中,液滴顶部局部表面温度最大,接触线处最小,且随蒸发的进行表面温度逐渐减小。液滴体积演变行为区别于亲水表面,这表明基板特性影响了液滴蒸发机理。液滴蒸发初始时刻,全局蒸发速率最大,随蒸发的进行,全局蒸发速率逐渐减小。液滴表面温度分布不均匀使得液滴表面产生了张力梯度,张力梯度引起了液滴内部流体流动;近气液界面处流体由液滴顶部向下流动,液滴内部流体由下向上流动,形成了Marangoni流。流体流动伴随着热量的传递,导致接触线附近温度较低,液滴内部中心处温度较高。     

微反应器内液滴生成规律及流动特性研究进展

微通道内两相流动广泛应用于微化工领域,本文简介了微通道内两相流动的形成过程,综述了国内外研究进展。进一步的研究需要结合数值模拟与理论研究的方法,以实验结果为基础,获得更为细致、可信的数学模型,为微化工优化设计提供基础。     

高压交流电场中单液滴变形度影响因素

采用不同的白油和水为实验介质对高压交流电场作用下单液滴的变形特性进行了研究。研究了电场强度、油品黏度、界面张力以及液滴直径等因素对液滴变形度的影响规律,并利用显微高速摄像系统结合图像处理技术对单液滴的变形规律进行了观察和分析。结果表明：液滴变形度主要受电场强度、液滴直径以及界面张力等的影响。与电场强度的N（1.7<N<2.4）次幂呈正比;与液滴直径近似呈线性关系;界面张力较低时,液滴更容易变形。油品黏度对液滴变形度没有明显影响。在变形度较小时,离心率和Weissenberg数具有较好的一致性,但We不适用于变形度较大的情况。     

微通道内卫星液滴生成机理与惯性分离机制

由于非线性动态特征,液液界面破裂过程常伴随卫星液滴的产生,对基于液滴的微流体技术生产液滴的均一性和精准化目标提出了挑战。阐释了微流体界面失稳的复杂动力学特征,剖析了界面失稳的影响因素,并分析了伴随界面失稳而产生的卫星液滴的现象与原理。结合惯性微流体新概念,总结了卫星液滴的惯性分离机制。展望了卫星液滴生成-惯性微流体分离一体化及其并行化数目放大的构想。相关工作的开展,有利于实现微流体技术生产单分散性液滴的精准化目标,为微流体与复杂流体相关的界面动力学行为与调控夯实基础。     

颗粒尾涡增强湍流的大涡模拟以及气固两相流中湍流变动的数值模拟

The turbulence enhancement by particle wake effect is studied by large eddy simulation （LES） of turbulent gas flows passing a single particle. The predicted time-averaged and root-mean-square fluctuation velocities behind the particle are in agreement with the Reynolds-averaged Navier-Stokes modeling results and experimental results. A semi-empirical turbulence enhancement model is proposed by the present-authors based on the LES resuits. This model is incorporated into the second-order moment two-phase turbulence model for simulating vertical gas-particle pipe flows and horizontal gas-particle channel flows. The simulation results show that compared with the model not accounting for the particle wake effect, the present model gives simulation results for the gas turbulence modulation in much better agreement with the experimental results.     

螺旋片导流式气液分离器的数值模拟与试验研究

The gas/liquid spiral separator, a key component in the compressed air system, was used to remove liquid and oil from gas stream by centrifugal and gravitational forces. To optimize the design of the separator, the relationship between the performance and structural parameters of separators is studied. Computational fluid dynamics （CFD） method is employed to simulate the flow fields and calculate the pressure drop and separation efficiency of air-liquid spiral separators with different structural parameters. The RSM （Reynolds stress model） turbulence model is used to analyze the highly swirling flow fields while the stochastic trajectory model is used to simulate the traces of liquid droplets in the flow field. A simplified calculation formula of pressure drop in spiral structures is obtained by modifying Darcy＇s equation and verified by experiment.     

使用加热空气的预混天然气催化燃烧的实验研究

In this paper the premixed catalytic combustion emissions such as CO, unburned hydrocarbon （UHC）, NOx and the temperature distribution in the catalytic monolith with ultra low concentration of Pd were studied. Three types of monoliths were used for experiments and the temperature of preheated air was respectively 50℃, 100℃ and 200℃. The results showed that preheated air made radial temperature in the catalytic monolith uniform which helped to avoid local hot spots so as to decrease NOx emission. The experiment also proved that the shorter monolith showed much better catalytic combustion performance than longer one and the temperature at the exit of the shorter monolith was relatively lower. On the contrary, the temperature was higher in the longer monolith and the lethal NOx emission was slightly increased.     

炭粒床高效工业除尘装置的设计与开发

The new dust removal technical route using the carbon-granular bed filter, packed of carbon particles with appropriate grade derive from an online-process vibration sieve, to replace the traditional baggy filter had been developed successfully for capturing the micro-carbon dusts produced from pulverization of petroleum coke,and the green close loop of carbon materials is thus completed in the combined pulverizing and classifying system and pulverized carbon dust removal process. The high dust removal efficiency greater than 99%, low outlet dust concentration less than 100 mg-m-S, low pressure drop through dust filtration chamber less than 980 Pa, simple and easy design, and flexible and stable operation were achieved also with the carbon-granular bed filter in both bench and industrial scale operations.     

在高压下规整填料中的流动实验研究

Both distillation performance and hydrodynamic study for backmixing by tracer technique were carried out in a high-pressure packed column with 0.15 m inner diameter over a wide range of operating conditions. Isobutane and n-pentane are employed as test mixture in the distillation experiment and air/water is used for the hydrodynamic study. The column is installed with Mellapak 350Y structured packing and the total packing height is 2.0 m. With the increasing operating pressure, the separation efficiency increases slightly while the F-factor corresponding to the maximum efficiency at each pressure is descending. It is noted that, at all operating pressures, with the increase of F-factor, the packing efficiency is slightly higher up to the flooding point. The application of SRP model to high-pressure distillation gives much lower values of HTUOG than those obtained experimentally. An additional term, the height of mixing unit, is introduced to correct the SRP model and improve its accuracy at high pressure. From the tracer experiments, the height of mixing unit for gas phase was found to be larger than that for the liquid phase. From this viewpoint, it is believed that the gas phase backmixing gives more unfavorable influence on the separation efficiency in comparison with liquid phase.     

壁面粗糙度对气粒两相流动中颗粒行为影响的实验研究

The effect of wall roughness on particle behavior in two-phase flows in a horizontal backward-facing step is studied using a phase-Doppler particle anemometer. The results show that the wall roughness widens the particle velocity probability density distribution, enhances the redistribution of particle velocity into different directions,reduces the particle longitudinal mean velocity and increases the longitudinal and transverse fluctuation velocities and Reynolds shear stress. The effect of roughness on particle motion in the recirculation zone is weaker than that in the fully developed flow region. The effect of roughness for small particles is restricted only in the near-wall region, while that for large particle diffuses to the whole flow field.     

水平管内气液段塞流液塞长度发展规律的实验和模拟研究

In petroleum industry, the slug flow is a fre-quently encountered flow regime in multiphase flowpipeline. For pipeline designers, the liquid slug lengthdistribution is important for the proper design ofdownstream facilities, such as slug catcher and sepa-ration system. However, for its transient and unsteadynature, it is a great challenge for engineers to correctlypredict the flow parameters of slug flow, especiallythe maximum liquid slug length. The unit cell model for slug flow in horizontal…     

Simulation of Aggregate Deformation and Breakup in Simple Shear Flows Using a Combined Continuum and Discrete Model

The evolution of aggregates suspended in liquid and subjected to simple (elongational) shear flows is reported under different shear rates and for varying strengths of interparticle interactions. This is carried out using simulations via the combined continuum and discrete model, offering a combined approach of distinct element method and computational fluid dynamics. In such a model, the motion of individual particles is obtained by solving Newton's second law of motion and flow of continuum fluid by the locally-averaged Navier–Stokes equations. The results demonstrate the dependence of both the dominating aggregate breakup mechanism and final aggregate morphology on shear rates and strength of interparticle interactions.     

气升式环流反应器内传质行为的分析与测量

1 INTRODUCTION Airlift loop reactors have emerged as one of the most promising devices in chemical, biochemical and environmental engineering operations. Its main ad-vantages over conventional reactors include excellent contact among different phases, ease of removal or replenishment of particles, and high heat and mass transfer rates[1]. High gas-liquid contacting area and favorable flow pattern are the attractive features of this type of three-phase contactors. Typical processes that ca…     

石油磺酸盐对原油界面性质及其乳状液稳定性的影响

The influence of petroleum sulphonate （TRS） on interfacial properties and stability of the emulsions formed by formation water and asphaltene, resin and crude model oils from Gudong crude oil was investigated by measurement of interfacial shear viscosity, interfacial tension （IFT） and emulsion stability. With increasing petroleum sulphonate concentration, IFT between the formation water and the asphaltene, resin and crude model oils decreases significantly. The interfacial shear viscosity and emulsion stability of asphaltene and crude model oil system increase for the petroleum sulphonate concentration in the range 0.1% to 0.3%, and decrease slightly when the concentration of the surfactant is 0.5%. There exists a close correlation between the interfacial shear viscosity and the stability of the emulsions formed by asphaltene or crude model oils and petroleum sulphonate solution. The stability of the emulsions is determined by the strength of the interfacial film formed of petroleum sulphonate molecules and the natural interfacial active components in the asphaltene fraction and the crude oil. The asphaltene in the crude oil plays a major role in determining the interfacial properties and the stability of the emulsions.