平底筒仓中心卸料流态演化过程及仓壁压力波动性  

Evolution process of center discharge flow pattern and pressure fluctuation of silo wall in a flat-bottomed silo

作　　者：刘克瑾 姚辉江 袁铮 LIU Kejin;YAO Huijiang;YUAN Zheng(College of Civil Engineering and Architecture,Henan University of Technology,Zhengzhou 450001,China)

机构地区：[1]河南工业大学土木工程学院,郑州450001

出　　处：《农业工程学报》2023年第15期15-24,共10页Transactions of the Chinese Society of Agricultural Engineering

基　　金：国家自然科学基金资助项目(51708183);河南工业大学高层次人才基金(31400375);河南工业大学创新基金支持计划专项资助项目(2022ZKCJ07)。

摘　　要：卸料时的仓壁压力是筒仓结构设计的关键,仓内物料的流动状态(流态)是影响卸料压力分布的关键。为了探究物料流态的演化过程和发生机理以及由此引发的仓壁压力分布情况,该研究采用自主设计的半圆柱形有机玻璃筒仓模型进行筒仓中心卸料试验和离散元(discrete element method,DEM)模拟分析。筒仓壁嵌入定制压力计,贮料为平均粒径3.5 mm的陶球,在测量仓壁压力分布的同时实时观测贮料内部和外部的流动过程。通过标定颗粒追踪贮料运动轨迹。通过PFC2D建立离散元数值模型,分析卸料过程中贮料的力链网络、速度矢量和孔隙率变化,探讨颗粒的运动机制和颗粒体系的传力方式。基于模型试验和数值模拟结果,根据颗粒物质力学、土力学和散体力学基本原理,从宏观和细观层面分析流态的演化过程和发生机理以及仓壁压力波动性规律,明确仓壁压力和流态的关系。结果表明:卸料瞬间(卸料率0~1%),强力链断裂导致孔隙率增大(由卸料前的0.15043~0.20030增至卸料瞬间的0.15136~0.23223),各测点仓壁压力骤增,P2测点(深度0.4 m)的增幅最大,达到1.94;卸料时贮料流态的演化过程为:整体流—漏斗流—混合流(漏斗流与管状流共存)—管状流,并以漏斗流和管状流为主,整体流阶段的仓壁压力波动性最大(0.2、0.4和0.6 m深度处的仓壁压力骤增至峰值1.65、3.63和4.05 kPa),颗粒流动呈现非线性;在贮料表面下降至高径比为1.04的位置,管状流开始出现,卸料时管状流道的直径逐渐减小(由270 mm减小至50 mm);贮料区域可划分为流动区、(准)静止区以及边界区,这些区域随着物料流出不断发展变化,流动区和静止区的交界位于距仓底0.329 m(约1/3高度)处。研究结果可为散体物料流态和筒仓散体物料压力分析提供参考。Silos are commonly used for the bulk storage of grain in agriculture.The pressure acting on the silo wall during silo discharging is one of the most important indicators during the structure design.The flow state of the material in the silo is the key influencing parameter on the distribution of discharging pressure.This study aims to explore the evolution of granular material flow patterns and the wall pressure distribution during silo discharging.A discharging test was performed on a 3D test silo to explore the flow of granular material with an average particle size of 3.5 mm.The plexiglass silo was designed semicylindrically with seven pressure sensors along the silo wall.The inner diameter of the test silo was 500 mm,the wall thickness was 20 mm,the height was 1100 mm,and the diameter of the outlet was 50 mm.Both the internal and the external flow of the granular material were observed to simultaneously record the wall pressure distribution.Meanwhile,the particle trajectory test was carried out to explore the mechanism of force transmission and the motion of granular particles.Furthermore,the discrete element method(DEM)was adopted to analyze the evolution of the force chain network,velocity vector and porosity of the granular material in store and during discharging.The results showed that the strong force chain fracture led to the increase of porosity(from 0.15043-0.20030 before discharging to 0.15136-0.23223 at discharging instant).The wall pressure increased sharply at the discharging instant(discharging rate 0%-1%),and the wall pressure increased the most(the pressure of the silo wall at the depth of 0.2,0.4 and 0.6 m increases sharply to the peak value of 1.65,3.63 and 4.05 kPa).The storage zone during discharging was divided into three zones,i.e.,the flow,the(quasi)static,and the boundary zone between them.These zones evolved,as the discharging developed.The intersectional interface between the flow and static zone was located at 0.329 m(about 1/3 height)from the silo bottom.Four flow patterns included

关 键 词：粮食 流态 筒仓 中心卸料 仓壁压力 力链网络 

分 类 号：S126[农业科学—农业基础科学]