对增阻系数法计算浆体管道阻力的研究

本文根据扩散理论相对体积浓度■的H.M．伊斯梅尔方程与E.J．瓦斯普和王绍周浆体流态判别标准,采用刘德忠对指数Z计算法进行浆体流态判别计算,得出似均质浆体体积浓度C_1V和非均质浆体体积浓度C_2V,依据浆体相对体积浓度■,提出C_1V粗细颗粒分界粒径概念,并在此基础上,提出C_2V非均质浆体体积浓度增阻概念,对分界粒径概念和增阻概念进行定义,推导出增阻系数法计算浆体管道阻力公式,该公式通过我国六条长距离浆体管道工程验证,计算结果与工程实际相近。     

均匀放矿过程中细粒冰碛物穿流机理试验研究

为探究均匀放矿过程中细粒冰碛物的穿流机理,以普朗铜矿地表细粒冰碛物为研究对象,利用室内三维物理模型试验方法,开展了细粒冰碛物覆盖层下的粗颗粒矿石均匀放矿试验研究。研究结果表明：均匀放矿过程中细粒冰碛物穿流机理主要受“孔隙填充机制”控制,其穿流程度取决于粗颗粒矿石放矿过程中随机产生的孔隙大小和数量;冰碛物颗粒粒径越小,其穿流速度越快,穿流效果越显著,穿流时间越短;根据试验过程中细粒冰碛物穿流规律,构建了细粒冰碛物穿流机理概化模型,结果显示细粒冰碛物和粗颗粒矿石相对运动是造成细粒冰碛物穿流的内在因素,细粒冰碛物和粗颗粒矿石相对运动越显著,细粒冰碛物穿流越明显。研究结果对揭示细颗粒穿流特性提供一定理论支撑,同时对细颗粒物质覆盖层下的崩落法矿山灾害防控及矿石贫化控制具有实际工程意义。     

钻孔水力采矿中气举模型的建立

为得到在钻孔水力开采关键设备中气举（气力提升装置）设计所需要的压降参数，建立了气举提升管内的气－液－固三相流压降数学模型。该模型基于压力能量消耗最小原理，得出了在环状流态时具有相对稳定的流动状态。针对在此流动状态下，通过对修正后的气－液和气－固两相流压降数学模型的叠加，得到了适合于对小颗粒、均匀粒径矿砂开采时，工作状态下的气举内气－液－固三相流压降数学模型。模型求解与实验结果表明，该模型计算结果与实验数据比较吻合。     

改善骨料级配的AQH堆积模型

已有骨料级配理论和堆积模型在解决不同颗粒的级配堆积问题上仍存在一定的局限性,为此,在粉体颗粒的Horsfield堆积模型基础上,优化其不连续级配,确定连续分布粒径区间Q,依据骨料粒度分布特征确定级配比例,由此提出AQH堆积模型。利用某种矿山骨料,对比几种连续级配理论各自适用性,在连续区间Q内几种级配理论确定的各粒径体积微分整体规律与基于骨料粒度分布的理想级配基本一致,即当细颗粒含量要求较高时,对粗颗粒含量要求较低。基于AQH模型的混合颗粒中,-37μm细颗粒部分体积微分有所增加,+225μm粗颗粒体积累计占比降低2.18%,其中-3.1μm细颗粒数目微分显著提高。将胶凝材料作为AQH模型中的细颗粒,根据骨料和胶凝材料相应粒径体积微分所确定的超定方程,利用MATLAB求出最小二乘解,确定骨料及胶凝材料各自质量百分比,基于此配方进行胶砂试验,7d强度0.52MPa,28d强度1.13MPa,就物理堆积效应而言,改善骨料粒径级配,对矿山充填工程胶砂试验参数比例确定有一定的意义。     

基于PIPSIM软件的多相管流模型优选

通过阅读大量中外文献,总结了4个多相管流压降模型Mukherjee-Brill相关式、Hagedorn-Brown相关式、Gray相关式、Anari相关式,根据误差分析法建立了多相管流计算方法综合评价模型,在此基础上,利用垂直井实测数据对工程上较常用的4种多相管流计算方法进行了评价,结果表明:TMB模型性能最佳,其次是ANSARI模型。     

燃煤电厂脱硫废水烟气蒸发特性流场模拟

喷雾液滴蒸发特性是实现电厂脱硫废水零排放烟气蒸发技术的关键。利用数值模拟的方法对气液两相流过程中涉及影响液滴蒸发特性的喷雾液滴平均粒径（分布特征）、传热传质等影响因素进行分析,建立喷雾液滴群烟气蒸发传热传质模型,获得了喷雾液滴群蒸发规律及运动特征。分析结果表明：模拟喷雾粒径情况下,液滴加热迅速,完全蒸发的关键控制步骤取决于液滴表面蒸汽气相组分浓度Ci,s与烟气中蒸汽气相组分浓度Ci,∞的浓度差,相同的烟气蒸发环境下,不同粒径组都呈现出初期快速蒸发和后期缓慢蒸发2个明显的阶段,在相同最大粒径范围下（最大直径100 μm）,细颗粒群（平均粒径24 μm）主体段蒸发时间最短（0.3 s达到80.1%的蒸发质量比）,粗颗粒群（平均粒径84 μm）蒸发质量比最大（0.6 s达到95%的蒸发质量比）。     

运用CFD对Buell型旋风分离器的模拟分析

运用数值模拟方法计算了颗粒在旋风分离器中的运动轨迹,得到了不同粒级的颗粒分离效率和分离器总压降,并将分离效率计算结果与Barth经验模型,压降计算结果与Dirgo经验模型计算值进行比较,发现运用CFD模拟计算与经验模型结果基本一致,分离效率略低、压降比较吻合。同时发现不同粒径颗粒逃逸的主要途径不完全相同,在入口上方或下部进入的离子逃逸概率较高。研究结果还表明,应用计算流体力学来研究旋风分离器的分离性能方便可行。     

水平圆管内固液两相流的压降及流型分析

采用Churchill所推导的固液两相流压降计算模型和欧拉双流体模型计算水平圆管中不同流速、固相体积百分数条件下浆体的压降,结合Kaushal et al的实验数据,验证比较了压降计算结果;通过欧拉双流体模型数值,模拟了不同流速、固相体积百分数下水平管中固液两相流浆体的流型及速度场分布,并对内部机理进行了简要讨论。研究结果能够为管道输送固体物料提供一定的参考。     

杜达铅锌矿粗骨料充填料浆流动性研究

杜达铅锌矿充填系统由于尾砂性质等原因,充填骨料不能采用单一的全尾砂或分级尾砂。根据现场情况决定在分级尾砂中掺入粗骨料(戈壁集料或水库沉砂),充填料浆由于粗骨料的掺入,骨料平均粒径变粗且级配发生变化,料浆和易性变差,易离析。为了研究"粗骨料充填料浆"的流变性能,现场采用了L管模型对充填料浆的流变参数进行了测定和计算。研究表明,当"粗骨料充填料浆"满足"结构流"所需的基本条件且浓度控制在一定范围内时,可以获得比较好的充填料浆流态。     

膏体充填料浆超细颗粒与流变特性关系研究

膏体充填料浆一般是使用尾砂和粗颗粒骨料制备的混合料浆体,充填材料的级配对料浆的流变特性有极大的影响。为了使研究更客观、更具有普适性,基于水力粗度定义了超细颗粒的粒径。基于流变试验结果进行相关性分析,得到超细颗粒的含量与膏体充填料浆的塑性黏度呈正相关;粗骨料的含量与膏体充填料浆的屈服应力呈正相关。建立了膏体充填料浆流变特性的回归分析模型,进一步验证了使用水力粗度定义超细颗粒的正确性。     

颗粒粒径对浮选机固—液两相流场分布特征影响研究

针对充气机械搅拌式浮选机,运用CFD流体模拟软件进行了颗粒粒径对浮选机固—液两相流场分布特征的影响研究。通过模拟分析可知:离散相矿物颗粒与连续液相两相之间相互作用较小,流场分布特征基本保持一致,微细粒矿物颗粒粒径对浮选机内部固—液两相流场特性影响较小。转子及定子表面压力分布值与颗粒粒径有较大的关系,且在此处区域附近湍流动能较大,保证了矿物颗粒在该区域的较好分散性。     

Particle collision modeling - A review

Over the past 100 years particle collision models for a range of particle inertias and carrier fluid flow conditions have been developed. Models for perikinetic and orthokinetic collisions for simple, laminar shear flows as well as collisions associated with differential sedimentation are well documented. Collision models developed for turbulent flow conditions are demarcated on the one side with the model of Saffman and Turner (1956) associated with particles exhibiting zero inertia and on the other side with the model of Abrahamson (1975) for particle velocities that are completely decorrelated from the carrier fluid velocities. Various attempts have been made to develop universal collision models that span the entire range of inertias in a turbulent flow field. It is a well-accepted fact that models based on a cylindrical as opposed to a spherical formulation are erroneous. Furthermore, the collision frequency of particles exhibiting identical inertias are not negligible. Particles exhibiting relaxation times close to the Kolmogorov time scale of the turbulent flow are subject to preferential concentration that could increase the collision frequency by up to two orders of magnitude. In recent years the direct numerical simulation (DNS) of colliding particles in a turbulent flow field have been preferred as a means to secure the collision data on which the collision models are based. The primary advantage of the numerical treatment is better control over flow and particle variables as well as more accurate collision statistics. However, a numerical treatment places a severe restriction on the magnitude of the turbulent flow Reynolds number. The future development of more comprehensive and accurate collision models will most likely keep pace with the growth in computational resources.     

Interference of coarse and fine particles of different shape in mixed porous beds and filter cakes

In solid–liquid separation the knowledge of solids packing structure is important to control permeability and dewaterability. In particular, cakes formed in filtration are often represented by the composition in coarse and fine particles. In this work cakes were modelled by mixing a bed of coarse (spheres) and fine (kieselguhr of three types and kieselgel) particles with a wide size distribution, in order to obtain beds with different proportions of plate and rod-like particles. Size ratio of glass beads to kieselguhr particles were in the range 23–30. Porosity and permeability were measured for a range of large particle fraction in the mixture from 0 up to 1.0. The fractional porosity of each particle fraction was introduced as a parameter. The approach proposed in this work was also successfully applied to different published filtration data. It was found that (1) the presence of more than 10% of fines in the coarse granular bed significantly reduces the cake permeability; (2) to improve cake permeability the volume fraction of filter aid in suspension must be at least 50–60% of total solid volume; (3) obtained data may be used to control the porosity of a mixture, if the fractional porosity of large and small particles is known or to estimate mixture tortuosity.     

CFD–DEM study of the effect of particle density distribution on the multiphase flow and performance of dense medium cyclone

A mathematical model is developed to study the coal-medium flow in a dense medium cyclone (DMC) of 1000 mm body diameter. In the model, the motion of coal particles is obtained using the Discrete Element Method (DEM) facilitated with the concept of “parcel–particle” while the flow of medium as a liquid-magnetite mixture Computational Fluid Dynamics (CFD) based on the local averaged Navier–Stokes equations. In addition the Reynolds Stress Model (RSM) is adopted to describe the anisotropic turbulence, the Volume of Fluid (VOF) model is used to describe the air-core position and multiphase mixture model used to estimate the flow of fine magnetite particles. The simulated medium and coal flows allow estimates to be made of pressure drop, efflux stream medium densities and partition curves for coal particles of different sizes and densities. These estimates are compared favourably with industrial scale measurements of a 1000 mm DMC operating under similar conditions. On this base, the effect of particle density distribution that represents the major difference between two major coal type, i.e., coking coal and thermal coal, is studied. The results are analysed in terms of medium flow pattern, particle flow pattern, partition performance and particle–fluid, particle–wall and particle–particle interaction forces.     

振动流化床加重质流动模型的研究

加重质的流动状态对振动流化床中细粒煤的有效分选起着决定性的作用，通过理论分析及试验研究，提出了以两个并联扩散模型的描述适合于细粒煤分选的振动流化床和重质流动模型，全面分析了振动参数，气流参数等对加重质流动模型的影响，得出了振动强度是决定如重质平均停留时间及有效的扩散系数的主导因素，并建立床层不同区域中振动强度与有效扩散系数的关系模型。     

Prediction of wear and its effect on the multiphase flow and separation performance of dense medium cyclone

Dense medium cyclone (DMC) is a high-tonnage device that is widely used to upgrade run-of-mine coal in modern coal preparation plants. It is known that wear is one of the problems in the operation of DMCs, but it is not well understood. In this work, the wear rate of DMC walls due to the impact of coal particles is predicted by a combined computational fluid dynamics and discrete element method (CFD-DEM) approach, using the Finnie wear model from the literature. In the CFD-DEM model, DEM is used to model the motion of discrete coal particles by applying Newton’s laws of motion and CFD is used to model the motion of the slurry medium by numerically solving the local-averaged Navier–Stokes equations together with the volume of fluid (VOF) and mixture multiphase flow models. According to the Finnie wear model, the wear rate is calculated according to the impact angle of particles on the wall, particle velocity during an impact and the yield stress of wall material; the relevant particle-scale information can be readily obtained from the CFD-DEM simulation. The numerical results show that the severe wear locations are generally the inside wall of the spigot and the outside wall of the vortex finder. The wear rate depends on both the operational conditions and solids properties. It increases generally with the decrease of medium-to-coal (M:C) ratio. For a given constant M:C ratio, the wear rate for thermal coal is higher than that for coking coal, especially at the spigot. Large particles may cause a non-symmetric wear rate due to the gravity effect. The effect of a worn spigot wall on the multiphase flow and separation performance is also studied. This work suggests that the proposed approach could be a useful tool to study the effect of wear in DMCs under different conditions.     

宽粒级煤浮选机流场数值模拟研究

将流态化机理与宽粒级煤浮选过程相结合,在一个浮选设备中实现细粒常规浮选与粗粒流态化浮选所需的不同流体力学环境,自行设计了一种新型宽粒级煤浮选机,并采用FLUENT 6.3.26软件进行数值模拟研究,从速度和湍流度两个方面对浮选机内流场进行分析。结果表明：在浮选机内增加格栅板后,可将浮选机内流场分为低速、弱湍流和高速、强湍流两个区域,从而可为粗、细颗粒浮选创造各自所需的流体力学条件;通过对叶轮圆周线速度比值与合速度比值和湍流强度比值变化规律的分析,找出浮选机模拟放大的运动相似准则。     

Numerical modeling of the coal-and-gas outburst gasdynamics

The article discusses the problem of coal outbursts into mined-out space based on the nonstationary and nonequilibrium velocity and temperature approach of the mechanics of inhomogeneous media, presents the math models with and without taking account of intergranular pressure of solid particles, and compares the new assessment with the available calculation and experimental references. Based on the analysis of the mixture flow behavior, the authors have found some rules in the relationships of depression waves, shock waves, initial concentration and diameter of particles in coal-and-gas mixtures.     

精确化装球方法的破碎统计力学原理分析

依据给矿粒度特性用破碎统计力学原理指导精确化配球,并对钢球精确化配比、偏大配比、偏小配比及现场配比这四种球径配比在冲击作用下钢球一个破碎周期中可能产生的破碎概率进行了计算。计算结果的对比显示,钢球精确化配比方案(推荐方案)的破碎概率最大。其原因是:在精确化配比方案下,各粒级矿粒所需钢球尺寸是根据实际矿石的力学特性,采用段氏半理论公式精确确定的,这样可保证精确的破碎力;再分别配以与粗、细矿粒百分率一致的各种钢球的适宜的个数时,可使破碎具有好的选择性,从而使各级别有最高的磨碎概率。     

Using SPH one-way coupled to DEM to model wet industrial banana screens

Large banana screens with multiple decks are used extensively in the process separation of many valuable export commodities. They are high capacity vibrating screens with a curved profile. Discrete Element Method (DEM) modelling using non-spherical particles has previously provided significant insight into the operation of these dry industrial screens. Here we introduce the use of Smoothed Particle Hydrodynamics (SPH) to model the flow of slurry (water and fine material) through a double deck banana screen. This paper firstly reports on the underlying DEM model of the coarse particulate flow on a full-scale banana screen. We then use Smoothed Particle Hydrodynamics (SPH) to model the transport of fine particle slurry over and through the double deck banana screen. Finally, we combine the DEM with SPH models using a one-way coupling to simulate the effects of adding a slurry flow to coarse particulates on the banana screen. The key outcomes from this study are that; SPH is ideally suited for the high speeds and the high fragmented and filamentary nature of the fluid flow through the screen deck openings; the fluid only (SPH) model of slurry behaves similarly to the DEM approach in that more fluid is screened as the velocity slows, except near the earlier panels on the top deck; and, use of a porous media derived from DEM in one-way coupled approach with SPH produces clear and reasonable changes in fluid structure, separation and wetting of the screens consistent with slurry behaviour. Specifically, the fluid layer was much thicker in the coupled case, with slurry being trapped inside a coarse particle bed and which is sensitive to the fluid viscosity.