料仓内稠密粉体卸料流动特性研究
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摘要
为了研究料仓内粉体卸料流动及混合特性,采用实验与模拟相结合的方法,利用粉体的溶解性质获得两种粉体卸料过程的混合曲线,并建立能够进行大规模数值计算颗粒间固相作用力的三维数学模型。该模型基于欧拉与拉格朗日相结合的方法,利用相邻网格间固相颗粒浓度梯度与颗粒平均速度梯度来描述颗粒间的固相作用力。结果表明:料仓半顶角与卸料口径对粉体卸料流率的影响的模拟结果与实验结果及Brown经验关联式预测值吻合较好。两种粉体卸料过程的混合指数随料仓半顶角的增加而减小,减小卸料口径时混合指数有所减小但减幅不大,表明增加料仓半顶角以及减小卸料口径均会促进两种粉体在卸料过程的混合。
In order to study the powder discharge flow and mixing characteristics in the hopper,the dissolution properties of powders were used in experiments to obtain the mixing curve of two kinds of powder during discharge processes.A three-dimensional numerical model was established for large-scale numerical calculation of solid-phase interaction between particles.The model was based on the combination of Euler and Lagrange methods.The interaction forces between particles were described as the concentration gradient of solid phase and the average speed gradient between adjacent grids.The results show that the simulation results of the influences of the half angle and the outlet size of hopper on the discharge rate of the powder are in good agreement with the experimental results and the Brown empirical correlation.The mixing index of two kinds of powder decreases with the increase of the half angle of the hopper.When the outlet diameter is reduced,the mixing index decreases but the decrement is small.It indicates that increasing the half angle of hopper and reducing the outlet diameter will enhance the mixing of the two kinds of powder during the discharge process.
In order to study the powder discharge flow and mixing characteristics in the hopper,the dissolution properties of powders were used in experiments to obtain the mixing curve of two kinds of powder during discharge processes.A three-dimensional numerical model was established for large-scale numerical calculation of solid-phase interaction between particles.The model was based on the combination of Euler and Lagrange methods.The interaction forces between particles were described as the concentration gradient of solid phase and the average speed gradient between adjacent grids.The results show that the simulation results of the influences of the half angle and the outlet size of hopper on the discharge rate of the powder are in good agreement with the experimental results and the Brown empirical correlation.The mixing index of two kinds of powder decreases with the increase of the half angle of the hopper.When the outlet diameter is reduced,the mixing index decreases but the decrement is small.It indicates that increasing the half angle of hopper and reducing the outlet diameter will enhance the mixing of the two kinds of powder during the discharge process.
引文
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[2] SALEHK,GOLSHAN S,ZARGHAMI R.A review on gravity flow of free-flowing granular solids in silos-basics and practical aspects[J].Chemical Engineering Science,2018,192:1011-1035.
[3] CUTRESS J,PULFER R.X-ray investigations of flowing powders[J].Powder Technology,1967,1 (4):213–220.
[4] GENTZLER M,TARDOS G.Measurement of velocity and density profiles in discharging conical hoppers by NMR imaging[J].Chemical Engineering Science,2009,64 (22):4463–4469.
[5] GRUDZIE? K,MAIRE E,ADRIEN J,et al.Analysis of funnel flow in rectangular silo based on ECT data[J].Nature,2010,5(12):681-694.
[6] ALBARAKI S,ANTONY S J.How does internal angle of hoppers affect granular flow?Experimental studies using digital particle image velocimetry[J].Powder Technology,2014,268(1):253-260.
[7] ARTONI R,SANTOMASO A,CANU P.Simulation of dense granular flows:Dynamics of wall stress in silos[J].Chemical Engineering Science,2009,64:4040-4050.
[8] ZHENG Q J,YU A B.Finite element investigation of the flow and stress patterns in conical hopper during discharge[J].Chemical Engineering Science,2015,129:49–57.
[9] ANAND A,CURTIS J S,WASSGREN C R,et al.Predicting discharge dynamics from a rectangular hopper using the discrete element method (DEM)[J].Chemical Engineering Science,2008,63:5821-5830.
[10] KETTERHAGEN W R,CURTIS J S,WASSGREN C R,et al.Predicting the flow mode from hoppers using the discrete element method[J].Powder Technology,2009,195:1-10.
[11] 袁竹林,孙珊珊.一种漏斗流中两种粉体混合特性的测量方法[P].中国:201310302786.8,2013-07-19.YUAN Zhu-lin,SUN Shan-shan.A method for measuring the mixing characteristics of two kinds of powders in a funnel flow[P].China:201310302786.8,2013-07-19.
[12] IORDANOFF I,KHONSARI M M.Granular lubrication:toward an understanding of the transition between kinetic and quasi-fluid regime[J].Journal of Tribology,2004,126(1):137-145.
[13] DA CRUZ F,EMAM S,PROCHNOW M ,et al.Rheophysics of dense granular materials:Discrete simulation of plane shear flows[J].Physical Review E,2005,72(2):021309.
[14] KOMATSU T,INAGAKI S,NAKAGAWA N,NASUNO S.Creep motion in a granular pile exhibiting steady surface flow[J].Physical Review Letter,2001,86(9):1757–1760.
[15] LAGRéE P Y,STARON L,POPINET S.The granular column collapse as a continuum:validity of a two-dimensional Navier-Stokes model with a,μ(i)-rheology[J].Journal of Fluid Mechanics,2011,686(6):378-408.
[16] MACAGNO E O.Historico-critical review of dimensional analysis[J].Journal of the Franklin Institute,1971,292(6):391-402.
[17] JENIKE A.W.Bulletin No.123:Storage and flow of solids[M].Salt Lake City:University of Utah,1964.
[18] GELDART D,ABDULLAH E,HASSANPOUR A,et al.Characterization of powder flowability using measurement of angle of repose[J].China Particuology,2006,4:104-107.
[19] WANG W,ZHANG J,YANG S,et al.Experimental study on the angle of repose of pulverized coal[J].Particuology,2010,8:482-485.
[20] 张月,乔晓磊,刘海玉,等.基于主成分分析的煤粉流动性实验研究[J].热能动力工程,2016,31(5):93-98.ZHANG Yue,QIAO Xiao-lei,LIU Hai-yu,et al.Experimental study of the flowability of pulverized coal based on an analysis of the principal components[J].Journal of Engineering for Thermal Energy and Power,2016,31(5):93-98.
[21] LEVINSON M,SHMUTTER B,RESNICK W.Displacement and velocity fields in hoppers[J].Powder Technology,1977,16:29-43.
[22] SNIDER D M.Three fundamental granular flow experiments and CPFD predictions[J].Powder Technology,2007,176:36-46.
[23] BROWN R L,RICHARDS J C.Kinematics of the flow of dry powders and bulk solids[J].Rheologica Acta,1965,4:153-165.
[24] BEVERLOO W A,LENINGER H A,VELDE V D.The flow of granular solids through orifices[J].Chemical Engineering Science,1961,15:260-269.