【作者】 赵伟；

【导师】 龚欣； 杨运信；

【作者基本信息】 华东理工大学 ， 化学工程， 2015， 硕士

【摘要】 采用计算颗粒流体力学(CPFD)方法模拟了料仓内颗粒下料流动,与实验室搭建料仓下料实验数据相互验证。首先研究了CPFD方法计算料仓下料过程模型参数设置,继而研究料仓结构、颗粒物性和通气对料仓下料影响。最后讨论了CPFD模拟工业级煤粉料仓的适用性。根据模拟获得的颗粒体积分数分布定义颗粒体积分数减小的界面为转换面。以转换面和料仓出口为界,划分三个区域：颗粒流区、悬浮流区和竖直管区。颗粒流区域：颗粒间摩擦占据主导地位,固相体积分数较高且维持不变,颗粒速度和气体速度逐渐缓慢的增加；悬浮流区域：固相体积分数显著降低,颗粒和气体速度急剧增加；竖直管区：固相体积分数进一步降低,颗粒速度增大并达到终端速度,气固速度差在出料口附近形成负压力梯度。研究料仓结构和颗粒物性对下料的影响。料仓内的转换面相对高度随着料仓出口直径增大而减小,趋近极值1.4。料仓出口颗粒速度与料仓出口直径的0.44次方呈正比。料仓半锥角增大,料仓内流型逐渐由质量流向漏斗流过渡。料仓内转换面高度几乎不随料仓半锥角变化。研究了不同类型颗粒的下料特征：D类颗粒膨胀率最大,C类颗粒料仓出口几乎不膨胀；A类颗粒料仓出口负压绝对值最大,D类颗粒压力基本保持常压。通气料仓设计存在经济气量、最优通气高度Ho/D和最大下料流率。按照重力下料的临界高度Hgc/D和通气的最优高度Ho/D分为三个区域：(1)HL/D<Hgc/D,下料流率小且稳定性低；(2)Hgc/D≤HLD<Ho/D,下料流率和临界高度随通气高度增加而增加；(3)HL/D≥Ho/D,下料流率随通气高度增加而减小,稳定性逐渐增加。更多还原

【Abstract】 This study investigated the applicability of computational particle fluid dynamic (CPFD) numerical scheme for simulating flows in a3-D hopper on the basis of the experiments. Firstly, the parameters in CPFD model for hopper discharge process were studied. In addition, the effects of hopper geometries, particle properties and aerate hopper were in vestigated. Finally, the applicability of simulating process of discharging pulverized coal in industrial-grade hopper by CPFD model was discussed.Based on particle volume fraction distribution by the simulation results, three flow regions (granular regime region, suspended regime region and standpipe region) were divided and flow characteristics in these regions were analyzed. It shows dense-flow and slow increase of particle and fluid velocity in the granular regime region, dilute-flue and fast increase of particle velocity in the suspended regime region and the negative pressure gradient in the standpipe, which was caused by the difference of gas-solid velocities.The relative height of critical surface decreased with increase of the outlet diameter of hopper, approaching the extreme value1.4. The particle exit velocity increased with the increase of hopper diameter0.5-power law. As hopper angle increased, the flow pattern in hopper transformed from mass-flow to funnel-flow. But the height of the critical surface hardly changed with the hopper angle. The discharge characteristics types of particle were found:Group D particle expansion rate was largest at hopper outlet. Group C particle volume fraction almost didn’t change at outlet in hopper. The absolute negative pressure at outlet in hopper was largest with group A particle discharge process,The discharge of glass beads from an aerated hopper under several aeration height and rates was studied. There were the economic aerating flow rate, the optical aerated height (Ho/D) and the largest discharge rate in aerated hopper. The optical aerated height was increased with the increase of the aerate flow rate. Three flow regions were developed by gravity discharge critical height Hgc/D and the optical aerated height (Ho/D).(1)HL/D<Hggc/D, the discharge rate is slow and poor stability;(2) Hgc/D<HL/D<Ho/D, the discharge rate and critical surface height increase with the aeration height.(3) HL/D≥Ho/D, as the aeration height increased, the discharge rate decreased and stability gradually increased.更多还原