宽粒度分布的细颗粒沉降

针对浆态床ＦＴ合成中液体蜡与细颗粒催化剂的分离，对与其粒径分布相似的细石英砂与水的体系的沉降分离进行了考察，用超声波浓度仪测定沉降过程中的颗粒浓度。由此得出了沉降过程的浓度场，并从沉降曲线可以看出宽粒度分布的沉降不同于相同或相近粒径的沉降，而且可得出颗粒浓度、悬浮液高度对沉降的影响情况     

低速回转圆筒内磷铵颗粒粒度分布规律研究

利用取样－筛分－称重的实验方法,提出固体颗粒在倾斜回转圆筒内的径向、沿弦长（料面）方向及轴向粒度分布规律,并得出混合粒径固体颗粒在倾斜回转圆筒内发生径向偏析和轴向偏析的结论。研究所用回转圆筒直径为６００ｍｍ,实验物料为不同粒度配比的磷酸一铵。研究结果对内分级内返料喷浆造粒干燥机的设计有指导意义。     

重力沉降原理在微粉和超细粉粒度分析中的应用

探讨了利用重力沉降原理对粉体颗粒粒度分布进行测试时 ,颗粒的布朗运动对测定精度的影响。并推导出常见的耐火材料粉体最小的测试颗粒粒径范围应为 0 .6～ 0 .95 μm。同时介绍了采用国产KCT - 1型沉降天平进行微粉与超细粉的粒度分布测定时的操作要点与技巧。并对测试过程中出现的异常现象和解决的方法进行了阐述     

NSKC—1型粒度分析仪测定水泥粒度分布及比表面积

粉体粒度的测量方法很多,常见的有筛分析法、Coulter法、激光散射法和沉降法等。目前在水泥工业中比表面的测定采用勃式透气法,而粒度分布的测定一般用筛分析及沉降天平粒度仪。筛分析只适用于粗粒度的测定,70μm以下的颗粒筛分十分困难,因而通常采用沉降天平进行水泥粒度分布的测定。     

废弃混凝土砂粉再利用分选技术初探*

本文通过研究固废混凝土初期深加工工艺和设备,对废弃混凝土再利用物料分选进行研究分析：大于2.36 mm较大颗粒采用机械筛分的方法,小于600 μm的微粉采用风力分选的方法;为解决1.18 mm颗粒分离问题,分选采用风选加机械同步分选模式,分离出1.18 mm切割粒径的产品。通过采用分选技术,区段内粒度控制严格,满足标准要求。     

窄筛分颗粒气固流态化特性数值模拟研究

为更好地指导工业生产,了解不同粒径颗粒在气固流化床中的状态以及流化床中颗粒分布情况,针对气固流化床中窄筛分颗粒流态化特性进行数值模拟研究。通过流场模拟软件分析在相同流化床中不同粒径段的颗粒(46～80、106～113、185～221μm)和不同流化床进气速度条件下所能达到的体积分数和流化床层高度以及达到这一指标所需时间,并采用欧拉-欧拉模型和SIMPLE算法计算不同气速条件下的颗粒体积分数、速度分布。结果表明,在相同气速条件下,颗粒粒径增大,导致流化床内颗粒体积分数最高点与最低点的差距变大,颗粒分布不均匀性增加,同时床层整体高度下降,床层内颗粒密度上升,颗粒体积分数下降,流化效果降低;相同颗粒粒径情况下,增加气速可降低流化床内部颗粒的体积分数,增加气体与固体颗粒的接触面积,增强流化效果,但减少了流化床内部颗粒速度矢量分布达到均匀的时间,颗粒分布不均匀性更加明显。     

激光衍射光散射法在聚氯乙烯树脂粒度分析中的应用

主要介绍激光衍射光散射法在聚氯乙烯树脂粒度分析中的应用。并与筛分法对照,比较了两种方法测得样品的平均粒径,分布宽度,三目集中率,同时论述了颗粒形态与加工性能之间的关系。     

微细物料颗粒大小的测定

介绍了小于75μm(主要是小于30μm)的微细物料颗粒的大小、形状和分布的表示方法,对测定微细物料颗粒粒度和分布的筛分法、沉降法、显微镜和电镜观测、图象分析以及激光粒度计、库尔特粒度计和表面积测定等方法作了较详细的介绍,着重于测试方法及技术、应用和发展,未涉及在线粒度分析。     

用显微镜测定陶瓷颜料的分散度

陶瓷颜料颗粒分散度的测定,对于指导颜料的生产和使用都具有其实际意义。测定颜料颗粒分散度的方法很多,诸如筛分法、沉降法、离心法、计数法等。而显微镜测量则是计数法中一种常用而重要的方法。它不     

厌氧颗粒污泥粒径分布的分析测试方法简介

厌氧颗粒化污泥的形成是UASB等高效厌氧反应器启动成功的标志,研究污泥颗粒化常用的手段就是测定反应器内污泥颗粒的粒径分布,测量颗粒污泥粒径的方法有沉降法、湿式筛分析法、显微镜法、图像分析和激光粒度测定法等。而湿式筛分析法是一种适合我国国情的方法。     

基于CFD的新型布浆器混合室结构

为了进一步改善新型布浆器的布浆性能,设计了单腔式混合室（混合室Ⅰ）、以两组支管为单位的多腔式混合室（混合室Ⅱ）及以单组支管为单位的多腔式混合室（混合室Ⅲ）,采用计算流体力学（CFD）方法对混合室内的流动特性进行了模拟。结果表明,单腔混合室内,由于平行射流组各股射流间的强烈干涉作用,导致各股射流向混合室中部聚集,造成出口处质量流量分布呈现中间明显高于两侧的状态。在多腔混合室Ⅱ内,每个混合腔内有两组射流,保证了浆料的良好混合,避免了射流在中部聚集的现象。在多腔混合室Ⅲ内,由于每个混合腔内只有一组支管射流,实现了互补混合过程,混合效果明显好于混合室Ⅰ和混合室Ⅱ。从质量流量分布看,混合室Ⅲ的分布曲线比混合室Ⅰ和混合室Ⅱ的更平缓,其最大偏差仅为0.254%,明显小于混合室Ⅰ的0.538%和混合室Ⅱ的0.294%,更接近于理论混合平均值和期望值。     

基于多孔介质模型的膜式氧合器内部流场分析

膜式氧合器内部流体运动特性对其性能有重要影响,利用计算流体力学（CFD）对氧合器模型进行流体动力学分析是预测其性能的重要方法之一。本文基于压降实验计算氧合器纤维束的黏性阻力系数,建立了各向同性多孔介质模型。采用RNGk-ε湍流模型对不同流量下氧合器内部流场进行计算,得到了血液速度、压力和壁面剪切应力分布云图。发现随着流量的增加,氧合器内部速度梯度分布形式基本保持不变,压力分布呈倾斜状态且逐渐减小,大部分压力损失位于纤维束内,其中53.3%位于氧合室,42.6%位于变温室。氧合器血液的入口及出口位置为血液损伤的高发区域。采用溶血数值预估模型计算得到了氧合器的标准溶血指数NIH。结果表明：在低流量1.65～3.00L/min下,各向同性多孔介质模型的模拟结果与实验结果基本一致,模拟数值与实验数值的偏差会随着液体流量的增加而变大;流量为1.65～6.00L/min时,标准溶血指数NIH为0.0084～0.0835g/100L,满足人体生理允许的使用范围。     

变压精馏分离乙醇-氯仿共沸物的动态特性

基于乙醇-氯仿二元共沸体系的压力敏感特性,利用Aspen Plus软件,以年度总费用(TAC)最小为目标函数,模拟和优化了变压精馏稳态工艺,所得乙醇和氯仿产品纯度均大于99.9%(质量分数).利用稳态模拟考察了不同热集成变压精馏工艺的经济性.利用Aspen Dynamics软件考察了不同热集成变压精馏工艺的动态特性,建立了不同热集成变压精馏工艺的稳健控制方案.结果表明:完全热集成工艺与无热集成和部分热集成工艺相比,经济性最优;组成-温度串级控制结构可较好地控制无热集成和部分热集成流程,压力-补偿温度控制结构在完全热集成工艺中可实现稳健的控制;虽然完全热集成工艺经济性最优,但部分热集成工艺的可控性优于完全热集成工艺.本文研究对工业分离含低碳醇的二元共沸物热集成变压精馏工艺有一定的参考价值.     

A computational study of combustion in compression ignition natural gas engine with separated chamber

The combustion process and fluid flow in a compression ignition natural gas engine with separated chamber are studied by coupling Multi-dimensional Computational Fluid Dynamic (CFD) code FIRE with detailed chemical kinetic mechanism. The calculated data are first validated by experimental data. Subsequently, Multidimensional simulations at a baseline condition are carried out to investigate combustion process, fluid flow, mixture formation and NO emission distribution in the chamber. Ultimately, parametric studies are conducted to illustrate the effect of some parameters on engine performance. The results show that calculated data are in good agreement with the experimental data. It is revealed that auto-ignition of natural gas occurs in separated chamber when the local mixture temperature reaches around 1300 K and engine performance has a strong dependency on some parameters, such as injection timing, composition of natural gas and initial temperature.     

Hydrodynamic analysis of a banbury mixer 2-D flow simulations for the entire mixing chamber

Banbury mixers are widely used in polymer processing. The mechanics of flow in the chamber of an internal mixer are complex and difficult to analyze due to the complicated geometry and the highly transient character of the flow. For this work, a fluid dynamics analysis package—FIDAP, using the finite element method, was implemented to simulate the flow patterns for a Banbury B mixer. A 2-D flow analysis was carried out for the whole mixing chamber with two counter-rotating rotors. A power-law model fluid was used to characterize the rheological behavior of the mixture. 18 different geometries were selected to represent the relative position of the two rotors during their revolution. Streamlines and pressure contours were plotted for each geometry. Transient pressure profiles at fixed locations in the chamber wall were compared with experimental data. The comparison shows good agreement between theoretical predictions and experimental observations.     

Rheological studies on a slurry biofuel to aid in evaluating its suitability as a fuel

Biomass is an often abundant, renewable, low ash and low sulfur fuel. Due to these properties, biofuels are promising alternatives for traditional petroleum-based fuel applications; however, traditional biofuels for internal combustion engines are not cost competitive with gasoline, diesel or fuel oils. One method to reduce the cost of biofuels is to use slurry fuels which have a potential lower cost than liquid biofuels due to high conversion efficiencies. Slurry biofuels, such as a mixture of corn and water, could provide a biofuel alternative for diesel engines, pressurized gasifiers and heating oil applications such as burners or gas turbines. Use of these biomass slurries poses important questions about their stability and suitability for practical applications in internal combustion engines and combustors.This work reports rheology data for stable corn-starch water slurries (CSWS) which used a polyacrylic acid thickener to eliminate settling of the slurry and to provide desirable shear-thinning behavior for most of the compositions evaluated. The effect of shear rate on the viscosity of the CSWS was studied using a BOHLIN-controlled stress (CS) rheometer. The well-known Ostwald—de Waele power law and Sisko models for viscosity fit the data. The effect of corn starch content, thickener content and temperature on the viscosity of CSWS was also studied. The favorable shear thinning properties were observed for starch contents up to 45% starch and should aid pumping, injection and spraying. The lower heating values of the slurries, however, are undesirably low.     

Measurements of pollen grain dispersal in still air and stationary, near homogeneous, isotropic turbulence

The dispersal of ragweed, pine and corn pollen as well as polystyrene spheres in still air and stationary, near homogeneous, isotropic turbulence (HIT) was investigated using high-speed, digital inline holographic cinematography enabling Lagrangian tracking of the particles. Mean still air settling velocities were similar as reported literature values. Small discrepancies were most likely related to species/size differences and water content of the grains. Near-HIT was generated by loudspeakers mounted on the corners of a 40 cm³ chamber and the turbulent flow field at the center of the chamber was validated using stereoscopic Particle Image Velocimetry (PIV). Results showed near homogeneity and near isotropy with mean velocities 5–10 times smaller than the corresponding rms values of velocity fluctuations. The turbulent kinetic energy dissipation rate was determined from the PIV data sets and used to calculate the Kolmogorov scales and Taylor microscales. Experiments were carried out for two different loudspeaker amplifications corresponding to Taylor microscale Reynolds numbers, R_λ=144 and 162, respectively. The mean settling velocity in turbulent conditions was in all cases higher than the corresponding still air value, the difference becoming smaller as particle Stokes numbers increased. For the present conditions, the still air particle settling velocity was lower than the rms values of air fluctuating velocities. As a result, dispersion was dominated by inertia and for a given R_λ, particle fluctuating velocity autocorrelations fell more rapidly as the particle Stokes number decreased; corresponding particle diffusion coefficients also decreased. Transverse particle diffusion coefficients were lower than those in the direction of gravity in agreement with the continuity effect. Under the present range of experimental parameters, results showed that inertial particles (0.6<St<11) in highly turbulent conditions disperse more effectively than the air.     

The University of Toronto Continuous Flow Diffusion Chamber (UT-CFDC): A Simple Design for Ice Nucleation Studies

A new instrument, the University of Toronto Continuous Flow Diffusion Chamber (UT-CFDC), has been designed to study ice nucleation at low temperatures. Based on previous continuous flow instruments, it is a parallel plate model that minimizes convective instabilities by operating horizontally with the warmer plate on top. A variable position sample injector can account for effects arising from gravitational settling of ice particles that form. The residence time in the chamber can vary between 2.6 to 25 s and ice particle formation is monitored with a two-channel optical particle counter. Observation of homogeneous freezing of 100 nm sulfuric acid aerosols was used to verify the accuracy of the calculated relative humidities (RHs) in the chamber to be ±4%, where we report onset RHs for 0.1% of the particles freezing in the temperature range of 218 to 243 K. We also show that the chamber accurately establishes conditions of water saturation by conducting water uptake studies onto sulfuric acid aerosol at 243 K. The two channel OPC allows for ice and water droplet formation to be distinguished under such conditions. The chamber is a simple, cheap, and small design that can be readily assembled for laboratory studies.     

Self-ignition and special features of flow in a planar vortex chamber

Regular self-ignition of hydrogen and kerosene was registered upon their mixing with oxygen-enriched air in a straight-flow vortex, chamber of planar-radial geometry. These fuel components were injected into the chamber from tanks with room temperature and pressure 4–10 MPa. The velocity, pressure, and temperature fields in the chamber were studied using experimental methods and numerical modeling on the basis of full Navier-Stokes equations. The measurment and calculation showed that a region of elevated temperatures appears in an unsteady vortex flow. The calculation was performed for Reynolds number up to 5·10³ and revealed an increase in temperature with increase in Reynolds number. Nevertheless, both the calculated and measured temperatures were lower than the known self-ignition temperatures. The nature of the ignition, observed remains unclear. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 6, pp. 26–41, November–December 1999.     

硝酸磷肥装置酸不溶物分离系统改造

介绍了硝酸磷肥装置酸不溶物分离系统存在的问题,通过对3种酸不溶物分离方法的对比,选择了重力沉降一洗涤法改造方案。介绍了沉降槽的设计条件,计算了酸不溶物的沉降速度和沉降面积,总结了改造效果。结果表明,改造后酸解液中酸不溶物质量分数从3．57％下降到2．77％,分离率为23％。