基于整体流型的粉体料仓设计分析

介绍了各种料仓流型,分析了影响料仓流型的因素,并应用到整体流料仓设计,在料斗形式、曲线、材料的选择以及改流体的设置上,作了详细的分析比较。     

粉体物料和料斗材料对料仓流型的影响

基于现有的实验数据 ,分析了粉体物料和料斗材料对料仓流型的影响。认为料仓设计的首选流型为整体流 ,形成整体流的料斗材料依次为不锈钢、铝合金、普通碳钢 ;料斗半顶角由实际物料和料斗材料确定。指出在一定半顶角下设计的“标准”整体流料仓 ,只适用于很小一部分粉体物料。     

粉体料仓的设计

介绍了料仓设计的基本方法, 包括流型选择、流型设计以及卸料口尺寸的确定方法等, 最后给出一个应用实例。     

CPFD在细颗粒料仓下料中的应用

借助计算颗粒流体力学(CPFD)的数值模拟方法,研究了细颗粒玻璃微珠在不同结构料仓内的下料特性,获得了料仓出口直径和半锥角对颗粒下料流动的影响。在实验室可视化下料平台开展了验证实验,模拟结果与实验结果吻合较好。模拟结果表明:下料流率与料仓出口直径2.5次方呈正比;料仓半锥角增大,下料流型从质量流过渡至漏斗流。CPFD模拟给出了料仓下料过程的细节信息,并获得了料仓结构对颗粒流动形态转变的临界面相对高度的影响。     

大型重力式散料掺混料仓及其工业应用

提出一种高效、节能、连续式散料掺混料仓 ,适用于PVC等粉、粒状颗粒的大批量掺混操作。料仓设计对均化管数量、进料口孔型、物料流型、布孔规律等作出了科学合理的设计 ,同时给出该掺混料仓在工业应用中的使用测定数据。这种结构的料仓 ,物料停留时间分布合理、出口混合度高、性能稳定、可一次性完成PVC颗粒的均化要求     

料仓卸料流动特性及结构强度数值模拟研究

采用离散元法建立颗粒模型研究锥形料仓卸料流动特性,通过DEM-FEM耦合的方法分析料仓结构强度,将无内构件料仓与带有内构件料仓卸料流动特性以及结构强度进行对比分析.结果 表明,无内构件料仓卸料过程出现中心流流型易发生堵塞,卸料速度慢,而带有内构件料仓卸料流型基本符合整体流流型;带有内构件料仓静态/动态侧压力小于无内构件...     

料仓设计中物料阻流问题的探析

本文通过分析料仓中物料的流型、阻流原因、提出设计中的考虑因素及预防措施。     

复杂流道结构料仓的下料流率预测

在实验室搭建的有机玻璃料仓下料平台上,分别以自由流动粉体玻璃微珠和黏附性粉体煤粉和聚氯乙烯为实验介质,针对无改流体(No-In)、封闭改流体(Con-In)和开放改流体(Ucon-In)三种情况所形成的不同流道结构,开展了粉体料仓下料及其流率建模研究,定量分析了改流体对粉体下料流率的促进作用,对比给出了玻璃微珠、煤粉和聚氯乙烯在不同流道结构料仓内的下料特性。研究表明,改流体的引入有利于提高料仓下料流率,Con-In促进流动效果最明显,对于流动性弱的煤粉,下料流率提升幅度达到最大的58%。基于剪切摩擦区的概念,提出流率校正因子F对最小能量理论方程进行了修正,将理想的料仓下料模型拓展至实际下料过程。进一步,对于Con-In,根据流道结构特征结合对粉体的受力分析,修正了模型中的锥角项;对于Ucon-In,基于粉体下料流动竞争机制,提出分阶段下料模式并关联了内层和夹层的下料流率,最终建立了复杂流道结构料仓的下料流率预测模型。该模型综合考虑了粉体物性、下料流型和流道结构的影响,可有效预测自由流动粉体和黏附性粉体流经传统料仓(No-In)和改流体料仓(包括Con-In和Ucon-In)的粉体下料流率,且预测偏差<10%。     

改善高压聚乙烯料仓吹风净化效果确保装置安全生产

分析了影响高压聚乙烯料仓安全使用的原因,找出了影响料仓吹风净化作用效果、引起料仓爆炸事故的原因,为此对料仓净化风入口元件进行了改造,并对改造效果进行了评价.     

楔形中心和偏心料仓中壁面摩擦系数对卸料速率的影响

采用离散元方法(DEM)研究了在不同的内摩擦系数、料仓半锥角和料仓宽度条件下,楔形中心料仓和偏心料仓中壁面摩擦系数对卸料速率的影响。研究发现,随着壁面摩擦系数的增加,两种料仓的卸料速率均先降低后稳定。当料仓从中心料仓变为偏心料仓时,壁面摩擦系数对卸料速率的影响程度以及卸料速率停止下降时的壁面摩擦系数的值都增大。随着内摩擦系数的减小或料仓半锥角的增大,壁面摩擦系数对卸料速率的影响程度以及卸料速率停止下降时的壁面摩擦系数的值都逐渐减小。增加料仓宽度能够削弱壁面摩擦系数对卸料速率的影响程度,但并不改变卸料速率停止下降时的壁面摩擦系数的值。     

Flow pattern measurement in a full scale silo containing iron ore

The flow pattern in a silo is important because it affects both the recovery of solids and the pressures on the silo wall during discharge. Wherever mass flow is not achieved, the boundary of the flow channel has significant implications for both the functional and structural design of the silo. Many techniques have been used for the study of flow patterns in model silos, but most cannot be used at full scale, and very few quality measurements at full scale have ever been made. This paper outlines a full scale experimental study in which the patterns of solids flow and the flow channel boundaries are reliably quantified.The full scale silo was specially designed, constructed and instrumented to exhibit funnel flow and to make observations of the solids flow pattern and the silo wall pressures. It had three outlets: one concentric, one fully eccentric and one in between. Three materials were used: iron ore pellets, slag fines and crushed basalt. This paper describes experiments involving iron ore pellets. The silo was seeded with radio frequency tags whose residence times were measured by detecting them on exit during discharge. The residence time data were studied to deduce the discharge flow pattern. This paper presents the results of three different flow pattern interpretation techniques: the best of them (mass-time relationships) is shown to give a very clear identification of the solids flow pattern and the flow channel boundary.     

从质量流向漏斗流转变过程中的动力学分析

球床模块式高温气冷堆的堆芯是全陶瓷型包覆铀燃料制成的球形颗粒,与石墨颗粒混合堆积而成,堆芯颗粒流的流态取决于颗粒尺度的平移、旋转等动力学量,以及力链、涡旋等介尺度物理量。为了分析颗粒的平移、旋转等动力学量对颗粒流流态的影响。基于筒仓颗粒流的物理模型,首先开展了筒仓颗粒流流变过程的实验测量,并使用基于 Hertz-Mindlin和 RVD （relative velocity dependent）滚动摩擦接触模型的离散单元法 （distinct element method, DEM）,研究了锥形筒仓颗粒流流变过程中球形颗粒的动力学量。进一步,基于DEM计算结果进行分析,发现筒仓自上而下呈现出质量流向漏斗流过渡的混合流状态。在筒仓混合流的不同流型区域中,平移速度和旋转速度之间的相关性是相反的;颗粒间的相对切向运动较大的区域集中在漏斗流区域与边壁区域。了解筒仓流变过程中颗粒的动力学特征,有助于优化筒仓颗粒流动,并减少颗粒表面的磨损。     

Numerical study on the behavior of funnel flow silos with and without inserts through a continuum hydrodynamic approach

In this paper the results from simulations performed using a hydrodynamic model proposed by Artoni et al. [Chem. Eng. Sci. 64 (2009a) 4040–4050] have been compared with published data of an extensive experimental investigation carried out at the Tel-Tek Research Institute in Porsgrunn, Norway. The experiments collected several data and observations on the wall stresses and the flow patterns observed during discharge of a full-scale funnel flow silo with and without inserts. The comparison between simulation and experiments showed the ability of the model to capture quantitatively the main features of both the flow and of the wall stress profiles when flow corrective inserts are put in the hopper of the silo in order to convert the discharge regime to a mass flow regime. Moreover information such as the stresses on the internals, which are difficult or impossible to get experimentally, have been collected from the simulations and discussed.     

Flow Channel Boundaries in Silos

The critical slip planes at the silo filling state are compared with the flow channel boundary during silo discharge for semi‐mass flows. The static critical slip planes are determined by using the dynamic programming method based on the stress field of granular solids stored in silos at the filling state. The flow channel boundary is estimated through the finite element analysis of the silo discharge. The results indicate that the critical slip line lies above the flow channel boundary. This characteristic can be attributed to the changeover of major principal stress directions of granular solids from the silo filling to the silo discharge. The analysis demonstrates that the silo wall friction tends to lift up the critical slip plane and flow boundary. A simple correlation is developed between the positions of critical slip planes and flow boundaries and is experimentally verified.     

Silo music — Mechanism of dynamic flow and structure interaction

This papers deals with the strong dynamic effects (called silo music) appearing during confined granular flow in the cylindrical silos. Silo experiments with dry cohesionless sand during gravitational outflow were performed in a cylindrical perspex model silo. During tests the wall accelerations and acoustic signals were recorded and the mode shapes of the silo structure were determined. In addition, experiments were performed with additional modifications of the silo structure and silo flow. A novel simple mechanism of the origin of silo music was proposed.     

Shape dependence of resistance force exerted on an obstacle placed in a gravity‐driven granular silo flow

Resistance force exerted on an obstacle in a gravity‐driven slow granular silo flow is studied by experiments and numerical simulations. In a two‐dimensional granular silo, an obstacle is placed just above the exit. Then, steady discharge flow is made and its flow rate can be controlled by the width of exit and the position of obstacle. During the discharge of particles, flow rate and resistance force exerting on the obstacle are measured. Using the obtained data, a dimensionless number characterizing the force balance in granular flow is defined by the relation between the discharge flow rate and resistance‐force decreasing rate. The dimensionless number is independent of flow rate. Rather, we find the weak shape dependence of the dimensionless number. This tendency is a unique feature for the resistance force in granular silo flow. It characterizes the effective flow width interacting with the obstacle in granular silo flow. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3849–3856, 2018     

Determination of bulk solid concentration changes during granular flow in a model silo with ECT sensors

Experiments in a cylindrical model silo were carried out with different initial densities of sand and silo wall roughness. Solid concentration changes during granular flow in the model silo were measured with electrical capacitance tomography (ECT) sensors. During silo flow, strong dynamic effects connected with booming sound occurred. Local one-dimensional (1D) and cross-sectional 2D evolutions of solid concentrations in dry sand during silo discharge were observed. The 1D phenomena were estimated from the raw data and the 2D phenomena were obtained from the reconstructed data by solving an inverse problem with a linear back projection algorithm.     

The simulation and experimental study of granular materials discharged from a silo with the placement of inserts

The simulation method of DEM and experimental method are used to investigate the flow pattern of the filling and discharging process for two-dimensional plane silos. Two kinds of inserts (conical insert and BINSERT®) are used in the silo to change the flow fields of the silo. The placement of inserts improves the flow behaviors of funnel flow type to mass flow type during discharging. The wall normal stresses are influenced by the change of the flow type. The effects of using differently shaped inserts on the flow pattern and wall stress are analyzed in this study. The controlling parameters include the silo half-angle, the orifice width, the shape of the insert and the properties of the granular materials. The simulation and experimental results are in good agreement.     

陶瓷粉料仓的设计与探讨

介绍了合理，经济地进行陶瓷材料仓设计的方法，探讨了粉料子内粉料流动状况对设计的影响。