四氢呋喃水合物浆流动特性

利用实验环道进行了水合物颗粒体积分数为0～65.2%的四氢呋喃(THF)水合物浆的流动实验。管道生成四氢呋喃水合物后,水合物浆的压降梯度随着流速的增加而增加;随水合物体积分数的变化存在一个临界体积分数,当管道中的水合物体积分数小于临界值时,压降随体积分数的增加而出现很小的增加,管道中水合物呈稀浆状,浆体为牛顿流体;当管道中体积分数大于临界值时,压降梯度随体积分数的增加急剧增加,管道中水合物呈泥状,浆体为Bingham流体。临界体积分数随着浆体流速的增加而增大,在0.5～3.5m/s的范围内,临界体积分数为39.4%～50.4%,文中回归了泥状水合物的屈服应力及表观黏度。并根据水合物浆的流动特性分段回归了水合物浆在管道中流动的压降计算公式,实验验证表明回归的计算公式可以比较准确地计算管道中水合物浆流动的压降,可以为THF水合物的流动及其它水合物浆的流动提供指导。     

放射性废树脂颗粒在垂直弯管内水力提升的分布仿真

针对放射性废树脂在垂直弯管内颗粒分布规律,采用计算机流体力学的方法对不同工况下的参数进行数值模拟和分析,以某品牌强酸性核级阳离子交换树脂和强碱性核级阴离子交换树脂为例,流体模型采用双欧拉模型,考虑湍流与重力的影响,使用COMSOL软件对废树脂和水在垂直弯管中的流动进行仿真,研究浆体流速、树脂密度、颗粒粒径、和体积浓度对垂直弯管内放射性废树脂颗粒分布的影响。研究结果表明:流速大对颗粒的均匀分布有利,树脂密度小对颗粒的均匀分布有利;颗粒粒径大小对树脂颗粒分布区域影响较小,但较大的粒径引起的颗粒浓度变化较大;较大体积浓度有利于对废树脂输送效率,但需考虑颗粒浓度大对管道的磨损影响。     

粗颗粒尾矿浆体管道输送速度分布规律研究

基于垂向剪应力呈线性分布假设,给出了零剪应力点的垂直位置计算方法和对应的最大剪应力计算方法,由此,通过借鉴普朗特半经验公式,给出了滑动床上方速度分布计算公式.通过粒径为1.71 mm的粗尾矿颗粒高浓度尾矿管道流动试验,测定了水平管道和倾斜管道中不同条件下若干组浆体速度分布试验数据.计算值和实测值的对比分析表明作者速度预测模型计算值与实测值较为一致,两者最大偏差不超过12.16％.作者速度分布公式的计算结果表明,随着管道倾角的增大而增大,最大速度点偏离管道中心之上的距离越来越大,同时速度分布变得越来越均匀.     

长距离浆体管道磨蚀率预测

长距离浆体管道的典型设计寿命通常为15至25年,故管道磨蚀率的确定对管道工程经济效益有较大影响.这里所说的磨蚀是化学腐蚀和物理磨损的综合表征,其中每个因素的影响大小与特定的管道输送工程相关,如细颗粒浆体管道输送工程,化学腐蚀在管道磨蚀中起主导作用,这类管线输送流速一般设计为1.5～2.5 m/s,为高度均质流,其管道底部与顶部磨蚀相差不多,对流速不敏感.但中、粗颗粒如原矿粉及尾矿的管道输送工程,管道的磨蚀方式与细颗粒浆体不同,其主要集中在管道的底部与弯头外弧侧,对流速较为敏感.细颗粒与中、粗颗粒浆体管道沿管线的磨蚀分布规律基本相似.     

非牛顿型浆体管道阻力降的一种简捷计算方法

本文根据浆体的流变参数，对工程中的非牛顿型均质浆体管道的阻力降，提出了一种简捷的计算方法。     

注浆减阻对顶管施工中磨擦阻力的影响

钢筋混凝土管道顶进施工中管道四周受周围土体摩擦影响,产生较大磨擦阻力阻止管道在顶进过程中运动。管道所受阻力的大小受多种因素的影响是比较复杂的。在相同的地质条件,施工技术,管道外径等客观素的情况下,采用触变泥浆减阻措施,可以减少顶进过程中的阻力,增加工作井顶进长度。     

矿浆管道输送临界流速试验研究

为了精确计算矿浆管道输送的临界流速,根据前人试验数据,分析了浆体浓度、管道直径、浆体粒径组成及浆体密度等对临界流速的影响,并进行机理分析。在研究前人计算临界流速公式的基础上,提出计算临界流速公式新模型及临界流速的新定义,通过量纲分析拟合出临界流速计算新公式,并对新公式进行验证。结果表明,临界流速随着浆体浓度和管径的增加而增大,随颗粒粒径和管径比值的增大而减小。本文的试验临界流速实测值与计算值最大误差为2.69%,平均误差为1.29%;文献中试验的临界流速实测值与计算值平均误差分别为4.18%、10.25%、11.45%;临界流速计算新公式平均误差均在12%以内,满足稀悬液浆体管道输送临界流速的预测要求。     

水合物浆体在水平细管中的流动相变换热

实验测量了质量分数为0~19.2%的TBAB水合物浆体在恒热流条件下在小管径内流动时的流动传热特性。利用数值计算获得管内浆体的沿程温度分布,在此基础上得到水合物浆体在小管径内的强制对流传热特性。结果表明加热功率对小管径管道中的浆体传热特性有较大影响;在层流状态下,流速对传热系数的影响相比紊流时要小。在实验数据基础上总结出了TBAB水合物浆体在小管径管内的对流换热经验关联式。     

水合物浆体在水平细管中的流动相变换热

实验测量了质量分数为0~19.2%的TBAB水合物浆体在恒热流条件下在小管径内流动时的流动传热特性。利用数值计算获得管内浆体的沿程温度分布,在此基础上得到水合物浆体在小管径内的强制对流传热特性。结果表明加热功率对小管径管道中的浆体传热特性有较大影响;在层流状态下,流速对传热系数的影响相比紊流时要小。在实验数据基础上总结出了TBAB水合物浆体在小管径管内的对流换热经验关联式。     

喷动床内气固二相流动行为的计算模拟

采用双流体模型结合颗粒动理学理论对喷动床内气固二相流体流动行为进行了计算模拟研究。模型中运用颗粒动理学理论描述颗粒相应力封闭流体控制方程,使用Gidaspow曳力模型描述气固相间作用。喷动床内颗粒在浓相区的体积分数很大,采用Schaeffer′s模型描述颗粒间的摩擦应力。模拟计算结果表明,喷动床内分喷射区、喷泉区、环隙区3个区域,在射流入口处形成一个瓶颈。模拟计算得到的颗粒速度和空隙度分布与实验数据进行比较,计算结果与实验结果吻合较好。     

Drag on individual cubic assemblies of spheres in non-newtonian tube flow

An obstacle in modeling aseptic processing of particulate foods is the lack of a reliable estimator for the drag force of the non-Newtonian liquid phase on the suspended particles as they flow through the holding tubes of such systems. The objective was to develop an expression for the drag force on cubic assemblies of spherical particles suspended in a pseudoplastic fluid flowing in a tube. An apparatus was assembled for direct measurement of the drag force exerted by solutions of sodium carboxymethyl cellulose (CMC) on the assemblies inside a tube. An empirical drag correction factor, as a function of particle volume fraction (applicable to Stokes' law), was developed.     

多孔介质内颗粒流动特性的格子Boltzmann模拟

地下岩石孔隙中小颗粒的运移和沉积会使得储层渗透性能降低,影响石油开发。为了探究悬浮颗粒在多孔介质中的流动过程,采用格子Boltzmann方法对三维多孔介质内流体和颗粒的运动过程进行了数值模拟,采用有限体积颗粒法构建多孔介质中骨架颗粒和悬浮颗粒。通过Half-Way反弹格式实现流体与颗粒间的相互作用,考虑孔隙结构、入口流速、孔隙率和颗粒直径对颗粒流动特性的影响,探究颗粒的运移和沉积规律。结果表明,入口速度对不同孔隙结构下颗粒的运动作用显著。随着入口速度增大,颗粒与颗粒、孔隙壁面以及流体之间的动量和能量交换作用增强,缩短了颗粒的运移路径,颗粒沉积率逐渐变小,颗粒拟温度增大。孔隙率的下降强化了颗粒间的碰撞,孔隙率由0.581降低至0.400,使得颗粒拟温度提升至9倍。颗粒拟温度随颗粒直径的增加而增加。但随着孔隙率增加,颗粒轴向速度增加,颗粒最高轴向速度可达入口流速的11倍,而颗粒接触力降低。     

水平气固两相高浓度输送流动机理

本文通过水平气固两相分层流动模型，分析了高浓度、高混合比、连续低速气力输送流动机理研究表明，稳定分层流动输送时，悬浮颗粒易集中于滑动床表面；层问颗粒剪切力是滑动床移动的上要驱动力；滑动床高度大于管道半径时将出现不稳定输送     

Elastohydrodynamics of concentrated suspension with generalized newtonian fluid medium

Lubrication theory is applied to compute the deformation of two approaching particles suspended in a Generalized Newtonian fluid with linear elastic theory estimating deformation and force on the particles with respect to deformability δ. The relative viscosity of concentrated suspension with deformable particles in a Generalized New-tonian fluid is obtained for a simple cubic array configuration by using the results of deformation and force for two particles. Since the deformation of particles generates the freedom of moving particles geometrically, the suspension with deformable particles shows shear thinning behavior.     

Flow of a gas-solid two-phase mixture through a packed bed

This paper is concerned with an upward co-current flow of a gas-solid two-phase mixture through a packed bed, a system employed in a number of industrial processes. Experimental work was carried out by using glass balls for packed bed, and both glass beads and FCC as suspended particles. The effects of solids loading and gas velocity on the pressure drop as well as the static and dynamic solid hold-ups within packed bed were examined. Experimental results showed different behaviour of the FCC from glass beads. At a given gas velocity, pressure drop increased approximately linearly with solids loading with a slope for FCC much higher than that for glass beads. The static hold-up of glass beads was much lower than corresponding dynamic hold-up at a given gas velocity, and it did not seem to change much with solids loading under the conditions of this work. At a given gas velocity, the static hold-up of FCC, however, was found to be comparable with the corresponding dynamic hold-up. An analysis was conducted on the pressure drop using a modified version of the Ergun equation by taking into account the effects of suspended particles on the viscosity and density, as well as the gravitational force. It was found that the modified Ergun equation agreed well with the experimental results of both this work and those reported in the literature. Effort was also made to develop relationships for the dynamic hold-up and the interaction coefficient between the suspended and the packed particles, the so-called solid-phase friction factor in the literature. The dynamic hold-up was found to increase with an increase in the product of velocity ratio of the solid to gas phases and the square root of the diameter ratio of the suspended to packed particles, whereas the interaction coefficient increased in general with increasing Froude number but with significant scattering.     

一级色谱纯乙腈的中试研究

本文主要介绍一级色谱纯乙 腈的中试研究。研究实验是 将纯度为98%的乙腈精制成 一级色谱试剂,通过大量的 实验和实验数据的分析比较 ,从而选择合理的实验方案 ,确定一级色谱纯乙腈试剂的 制备方法 。     

Cell manipulation in ultrasonic standing wave fields

Particles suspended in either travelling or standing wave fields experience non-zero time averaged radiation forces. In a standing wave field such forces can result in migration of the particles to preferred positions separated by distances of half an acoustic wavelength. Radiation forces also give rise to either interparticle attraction or repulsion and can exert a torque on suspended particles. The forces depend on some or all of the following properties (i.e. particle size and shape, sound frequency, the square of the sound pressure amplitude) and on the differences between the density and compressibility of the particles and those of the suspending phase. The forces acting on suspended particles are analysed and threshold pressures for the migration of particles to half-wavelength separations are derived. It is shown that appropriate choice of sound pressure amplitude should lead either to separation of particles of different densities and compressibilities in the sound field or to concentration of mixed samples essentially at the same location. Experimental observations of ultrasonic radiation force effects on cells are reviewed as are applications of radiation forces to effect cell concentration in electrofusion procedures and the use of ultrasound to support cells away from solid surfaces. Examples of cell concentration, cell alignment and cell-cell interaction are presented.     

IDENTIFICATION AND CORRELATION OF MIXING TIMES IN OPPOSED-JET MIXERS

This article deals with the theoretical investigation of the effect of suspended particles on the marginal stability of a double-diffusive ferrofluid layer with internal angular momentum heated from below subjected to a transverse uniform magnetic field. For a flat fluid layer contained between two free boundaries, an exact solution is obtained using a linear stability analysis theory and normal mode analysis method. For the case of stationary convection, the effect of various parameters like suspended particles, solute gradient, magnetization, coupling parameter, spin diffusion parameter, and heat conduction parameter has been analyzed. The critical magnetic thermal Rayleigh number for the onset of instability is also determined numerically for sufficiently large values of magnetic parameter M₁ and results are depicted graphically. It is observed that the critical magnetic thermal Rayleigh number is reduced because the heat capacity of clean fluid is supplemented by that of the suspended particles. The principle of exchange of stabilities is found to hold true for the ferrofluid with internal angular momentum in the absence of suspended particles, solute gradient, coupling parameter, and microinertia. Oscillatory modes are introduced due to the presence of the suspended particles, solute gradient, coupling parameter, and microinertia, which were nonexistent in their absence. The sufficient conditions for the nonexistence of overstability are also obtained.     

絮凝剂对过滤过程中悬浮颗粒剥离的影响

根据试验数据探讨了絮凝剂对过滤过程中悬浮颗粒剥离的影响，试验结果表明：上向流聚苯乙烯滤料直接过滤时，附着于滤料之上的悬浮颗粒是否剥离，与过滤过程中投加的絮凝剂种类和投加量密切有关。