Flow characteristics of granule discharged from eccentric wedge-shaped feed hopper

doi:10.11949/j.issn.0438-1157.20170852

Abstract

Abstract:

Flow field distributions of discharging various sized granular materials from wedge-shaped feed hopper was numerically simulated using three-dimensional discrete element method. A mathematical model of mass flow index (MFI) was proposed for the wedge-shaped feed hopper. The discharge flow pattern and its relationship with discharge mass flow rate was analyzed, and model reliability was verified experimentally. The results show that granular flow field in the hopper has a high velocity region near feed pipe outlet and is radially attenuated towards low velocity region at the upper hopper which is away from vertical wall and feed pipe. The flow direction of particles in high velocity region was well consistent, whereas granular flow in low velocity region exhibited local vortices. With the increase of particle size, overall flowability of particles in the hopper decreased, which high velocity region shrinked, low velocity region enlarged, and transition region became obscure, hence both MFI and discharge mass flow rate were decreased. When particle size was no more than 10 mm, MFI was negatively linearly related to particle size, but was positively linearly to discharge mass flow rate.

Key words: numerical simulation, experimental validation, granular flow, eccentric, discharge, particle size

摘要：

采用三维离散单元法，研究了偏心楔形喂料斗中不同粒径颗粒卸料过程的流场分布，建立了适用于偏心楔形喂料斗的整体流系数模型，分析了料斗卸料流型以及卸料流型与卸料质量流率的相关性，并通过实验验证了离散元模型的可靠性。结果表明：偏心楔形喂料斗内颗粒流场分布以靠近喂料管口区域为高速区，并呈辐射状朝远离垂直壁面端的料斗上部低速区过渡，高速区颗粒流场的整体一致性好，低速区颗粒流场呈局部涡流状；颗粒粒径增大，颗粒整体流动性变差，高速区域范围减小，低速区域范围增大，过渡区域变模糊；当颗粒粒径不大于10 mm时，整体流系数与颗粒粒径呈线性负相关，卸料质量流率与整体流系数呈线性正相关。

关键词: 数值模拟, 实验验证, 颗粒流, 偏心, 卸料, 颗粒粒径

CLC Number:

TQ051

LIU Yilun, LIU Siqi, ZHAO Xianqiong, LIU Chi, ZHANG Zhe. Flow characteristics of granule discharged from eccentric wedge-shaped feed hopper[J]. CIESC Journal, 2018, 69(4): 1469-1475.

刘义伦, 刘思琪, 赵先琼, 刘驰, 张喆. 偏心楔形喂料斗卸料过程中颗粒流动特性[J]. 化工学报, 2018, 69(4): 1469-1475.

References 30

[1]	VIDAL P, GALLEGO E, GUAITA M, et al. Finite element analysis under different boundary conditions of the filling of cylindrical steel silos having an eccentric hopper[J]. Journal of Constructional Steel Research, 2008, 64(4):480-492.
[2]	YU Y, SAXÉN H. Segregation behavior of particles in a top hopper of a blast furnace[J]. Powder Technology, 2014, 262:233-241.
[3]	KETTERHAGEN W R, HANCOCK B C. Optimizing the design of eccentric feed hoppers for tablet presses using DEM[J]. Computers & Chemical Engineering, 2010, 34(7):1072-1081.
[4]	LIU S D, ZHOU Z Y, ZOU R P, et al. Flow characteristics and discharge rate of ellipsoidal particles in a flat bottom hopper[J]. Powder Technology, 2014, 253:70-79.
[5]	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(24):5821-5830.
[6]	HÖHNER D, WIRTZ S, SCHERER V. A numerical study on the influence of particle shape on hopper discharge within the polyhedral and multi-sphere discrete element method[J]. Powder Technology, 2012, 226:16-28.
[7]	许鹏凯, 段学志, 钱刚, 等. 楔形中心和偏心料仓中壁面摩擦系数对卸料速率的影响[J]. 化工学报, 2015, 66(3):880-887. XU P K, DUAN X Z, QIAN G, et al. Granular discharge from concentric and eccentric wedge shaped hoppers:effect of wall friction coefficient on discharge rate[J]. CIESC Journal, 2015, 66(3):880-887.
[8]	张西良, 张建, 李萍萍, 等. 粉体物料流动性仿真分析[J]. 农业机械学报, 2008, 39(8):196-198. ZHANG X L, ZHANG J, LI P P, et al. Simulation analysis for particle material flow[J]. Transactions of the Chinese Society for Agricultural Machinery, 2008, 39(8):196-198.
[9]	JENIKE A W. Gravity flow of bulk solids, bulletin No. 108[J]. Bulletin of the University of Utah, 1961, 52(29):1-32.
[10]	JENIKE A W. Storage and flow of solids, bulletin No. 123[J]. Bulletin of the University of Utah, 1964, 53(26):229-236.
[11]	谭援强, 肖湘武, 郑军辉, 等. 锥形改流体下部孔径对筒仓卸料流态的影响[J]. 农业工程学报, 2016, 32(19):82-87. TAN Y Q, XIAO X W, ZHENG J H, et al. Effect of outlet diameter of cone-in-cone insert on silo flow pattern[J]. Transactions of the Chinese Society for Agricultural Machinery, 2016, 32(19):82-87.
[12]	谭援强, 郑军辉, 张浩, 等. 基于离散元法的锥形筒仓中颗粒流体的数学模拟[J]. 过程工程学报, 2015, 15(6):916-922. TAN Y Q, ZHENG J H, ZHANG H, et al. Mathematical simulation of granular fluid in conical silo based on discrete element method[J]. The Chinese Journal of Process Engineering, 2015, 15(6):916-922.
[13]	GONZÁLEZ-MONTELLANO C, GALLEGO E, RAMÍREZ-GÓMEZ Á, et al. Three dimensional discrete element models for simulating the filling and emptying of silos:analysis of numerical results[J]. Computers & Chemical Engineering, 2012, 40(40):22-32.
[14]	MAGALHÃES F G R, ATMAN A P F, MOREIRA J G, et al. Analysis of the velocity field of granular hopper flow[J]. Granular Matter, 2015, 18(2):1-7.
[15]	WU J T, CHEN J Z, YANG Y R. Microscopic analysis of particle flow in moving bed[J]. Journal of Zhejiang University, 2006, 40(5):863-864.
[16]	XU P, DUAN X, QIAN G, et al. Dependence of wall stress ratio on wall friction coefficient during the discharging of a 3D rectangular hopper[J]. Powder Technology, 2015, 284:326-335.
[17]	WANG P, ZHU L, ZHU X. Flow pattern and normal pressure distribution in flat bottom silo discharged using wall outlet[J]. Powder Technology, 2016, 295:104-114.
[18]	GONZÁLEZ-MONTELLANO C, RAMÍREZ Á, GALLEGO E, et al. Validation and experimental calibration of 3D discrete element models for the simulation of the discharge flow in silos[J]. Chemical Engineering Science, 2011, 66(21):5116-5126.
[19]	KRUGGEL-EMDEN H, RICKELT S, WIRTZ S, et al. A numerical study on the sensitivity of the discrete element method for hopper discharge[J]. Journal of Pressure Vessel Technology, 2009, 131(3):31211.
[20]	KETTERHAGEN W R, CURTIS J S, WASSGREN C R, et al. Modeling granular segregation in flow from quasi-three-dimensional, wedge-shaped hoppers[J]. Powder Technology, 2008, 179(3):126-143.
[21]	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):1-10.
[22]	CUNDALL P A, STRACK O D L. A discrete numerical model for granular assemblies[J]. Geotechnique, 1979, 29(1):47-65.
[23]	JOHNSON K L. Contact mechanics[J]. Journal of Tribology, 1985, 108(4):464.
[24]	MINDLIN R D, DERESIEWICA H. Elastic spheres in contact under varying oblique forces[J]. Journal of Applied Mechanics, 1953, 20(3):327-344.
[25]	中南大学. 一种多功能烟花亮珠造粒安全配料机构:2016214062845[P]. 2017-06-27. Central South University. A multi-functional fireworks beads granulation safety batching mechanism:2016214062845[P]. 2017-06-27.
[26]	CHEN H, ZHAO X Q, XIAO Y G, et al. Radial mixing and segregation of granular bed bi-dispersed both in particle size and density within horizontal rotating drum[J]. Transactions of Nonferrous Metals Society of China, 2016, 26(2):527-535.
[27]	CHEN H, LIU Y L, ZHAO X Q, et al. Numerical investigation on angle of repose and force network from granular pile in variable gravitational environments[J]. Powder Technology, 2015, 283:607-617.
[28]	陈辉, 肖友刚, 赵先琼, 等. 回转窑内二元颗粒物料的径向混合[J]. 工程科学学报, 2016, 38(2):194-199. CHEN H, XIAO Y G, ZHAO X Q, et al. Transverse mixing of binary solid materials in a rotating kiln[J]. Chinese Journal of Engineering, 2016, 38(2):194-199.
[29]	FUNG W W S, KWAN A K H. Effect of particle interlock on flow of aggregate through opening[J]. Powder Technology, 2014, 253:198-206.
[30]	陶贺, 钟文琪, 张勇, 等. 异形混合非球形颗粒在移动床中流动特性的数值模拟[J]. 科学通报, 2015, 60(27):2667-2675. TAO H, ZHONG W, ZHANG Y, et al. Numerical simulation of flow characteristics for non-spherical particle mixture flowing in moving bed[J]. Chinese Science Bulletin, 2015, 60(27):2667-2675.