浮选机流场数值模拟与相似特征参数的研究
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摘要
XJM-S系列浮选机是广泛应用于选煤生产的一种机械搅拌式浮选机,利用计算流体力学软件FLUENT模拟分析了XJM-S8型浮选机的流场特性。应用PRO/E软件建立了浮选机实体三维模型,应用GAMBIT软件对流场计算域进行网格划分,采用有限体积法作为离散化方法,选用标准k-ε湍流模型,以清水为介质,模拟分析了浮选机流场特性。通过数值模拟,得出了叶轮-定子区域压力分布图,浮选槽内不同剖面上液体流线图、速度分布图,以及湍动能、湍流强度、湍流耗散率等特征参数的分布状态及其变化规律。通过对叶轮-定子区域的模拟分析,发现在叶轮相同半径处叶片背液面动压总是高于迎液面,表明背液面流速高于迎液面流速;当流体进入定子时,受定子叶片阻碍作用速度下降,动能转换为压能;叶片流道中动压、静压、全压的最大值分别为36.6kPa、28.9kPa、60.4kPa,最小值分别为3.0kPa、-35.3kPa、-31.2kPa;在叶轮区域内流体的最大速度为8.56m/s,接近于叶轮圆周速度8.9m/s。通过对浮选槽内流体的流线图分析,发现流动状态呈“W”形立体循环运动,下部为纵向涡流运动,上部流动平稳,符合浮选过程要求;液流通过定子后,在稳流板导向作用下沿水平断面分布均匀,无死区,浮选机结构合理。通过对湍流特征参数的分析,发现湍动能、湍流强度、湍流耗散率关于叶轮中心呈对称分布;XJM-S8型浮选机的搅拌区域在槽体下部0.7m以下,在0.7m以上部分处于相对平稳的浮选分离区域,搅拌区域的湍流强度约为浮选分离区域的6倍;湍流强度与叶轮圆周速度成正比,以叶轮圆周速度恒定作为XJM-S型浮选机模拟放大运动相似准则,可保证相似的湍流强度。通过浮选机流场数值模拟分析,对XJM-S型浮选机的流场特征有了比较深刻的认识,为该类型浮选机的研究与优化设计奠定了一定理论基础。
XJM-S series flotation cell is a kind of mechanical-stirring type flotation machine, which is widely applied in coal preparation. In this paper, Fluid Mechanics software FLUENT was used to analyze the fluid field characteristics of the XJM-S8 flotation cell. And software PRO/E was applied to set up 3-D entity model. While software GAMBIT was served for grid partition in the calculation region. This paper adopted finite volume method as discretization method, selected the standard k-εturbulent flow model as well as used pure water as medium to simulate and analyze the characteristics of the flotation cell. By numerical simulation, the pressure distribution of the impeller-stator region, the streamline diagram as well as the speed distribution graph of the liquid at different sections within the flotation cell could be obtained. In addition, the distribution and the evolution pattern of the turbulent kinetic energy, turbulence intensity, turbulence dissipation rate and other characteristics parameters could also be gained. Through the impeller-stator region simulation analysis, it was found that, at a certain radius of the impeller blade, the dynamic pressure against the liquid surface was always higher than that on the liquid surface, indicating that the liquid flow velocity against surface was higher than that on the liquid surface; When the fluid entered the stator, the speed decreased due to the hindering effect of the impeller, correspondingly kinetic energy converted to pressure energy. The maximum value of the dynamic pressure, static pressure and total pressure in the blade runner were respectively 36.6kPa、28.9kPa、60.4kPa, while the minimum were respectively 3.0kPa、-35.3kPa、-31.2kPa. The maximum speed of the fluid in the impeller region was 8.56m/s, which was close to the rotational speed of the impeller 8.9m/s. Through the analysis of the fluid stream line in the flotation cell, it was found that the flow state was "W"-shaped three-dimensional of periodical movement. The lower part was vertical eddy movement while the upper flow was steady, which is consistent with the flotation process requirements. After the flow got through the stator, the flow was evenly distributed along the horizontal section the due to the orientation of the eddy plate flow board, there was no dead zone, indicating the structure of flotation machine is reasonable. Through the analysis of turbulence characteristic parameters, it was found that turbulent kinetic energy, turbulence intensity, turbulence dissipation rate distribute symmetry to the impeller center; The stirring region of the XJM-S8 flotation machine lied below 0.7m in the lower part of the regional body, while above 0.7m or more, it was the flotation separation region which was relatively stable. The turbulent intensity of the stirring region was six times than that of the flotation separation region. Turbulence intensity is proportional to the speed of the speed of the impeller. The constant rotational speed of the impeller is a similar criterion to the simulation of enlarged movement of XJM-S-type flotation machine to ensure similar turbulence intensity. Through numerical simulation of flow field analysis, characteristics of the flow field of XJM-S-type flotation cell can be deeply understood so that a certain theoretical foundation of the research and optimized design of flotation cell has been laid.
XJM-S series flotation cell is a kind of mechanical-stirring type flotation machine, which is widely applied in coal preparation. In this paper, Fluid Mechanics software FLUENT was used to analyze the fluid field characteristics of the XJM-S8 flotation cell. And software PRO/E was applied to set up 3-D entity model. While software GAMBIT was served for grid partition in the calculation region. This paper adopted finite volume method as discretization method, selected the standard k-εturbulent flow model as well as used pure water as medium to simulate and analyze the characteristics of the flotation cell. By numerical simulation, the pressure distribution of the impeller-stator region, the streamline diagram as well as the speed distribution graph of the liquid at different sections within the flotation cell could be obtained. In addition, the distribution and the evolution pattern of the turbulent kinetic energy, turbulence intensity, turbulence dissipation rate and other characteristics parameters could also be gained. Through the impeller-stator region simulation analysis, it was found that, at a certain radius of the impeller blade, the dynamic pressure against the liquid surface was always higher than that on the liquid surface, indicating that the liquid flow velocity against surface was higher than that on the liquid surface; When the fluid entered the stator, the speed decreased due to the hindering effect of the impeller, correspondingly kinetic energy converted to pressure energy. The maximum value of the dynamic pressure, static pressure and total pressure in the blade runner were respectively 36.6kPa、28.9kPa、60.4kPa, while the minimum were respectively 3.0kPa、-35.3kPa、-31.2kPa. The maximum speed of the fluid in the impeller region was 8.56m/s, which was close to the rotational speed of the impeller 8.9m/s. Through the analysis of the fluid stream line in the flotation cell, it was found that the flow state was "W"-shaped three-dimensional of periodical movement. The lower part was vertical eddy movement while the upper flow was steady, which is consistent with the flotation process requirements. After the flow got through the stator, the flow was evenly distributed along the horizontal section the due to the orientation of the eddy plate flow board, there was no dead zone, indicating the structure of flotation machine is reasonable. Through the analysis of turbulence characteristic parameters, it was found that turbulent kinetic energy, turbulence intensity, turbulence dissipation rate distribute symmetry to the impeller center; The stirring region of the XJM-S8 flotation machine lied below 0.7m in the lower part of the regional body, while above 0.7m or more, it was the flotation separation region which was relatively stable. The turbulent intensity of the stirring region was six times than that of the flotation separation region. Turbulence intensity is proportional to the speed of the speed of the impeller. The constant rotational speed of the impeller is a similar criterion to the simulation of enlarged movement of XJM-S-type flotation machine to ensure similar turbulence intensity. Through numerical simulation of flow field analysis, characteristics of the flow field of XJM-S-type flotation cell can be deeply understood so that a certain theoretical foundation of the research and optimized design of flotation cell has been laid.
引文
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[2]刘峰.选煤技术的现状及发展趋势.中国煤炭学会第六次全国会员代表大会暨学术论坛论文集[M].2007.
[3]谢广元主编.选矿学[M].中国矿业大学出版社,2000.
[4]石春辉.浅析浮选选煤技术发展趋势[J].洁净煤技术,2007,13(2).
[5]谢冬梅,崇立芹.煤用浮选机的使用现状及技改措施探讨[J].煤炭加工与综合利用,2006(3).
[6]郭梦雄.浮选[M].中国矿业大学出版社,2000.
[7]刘炯天等.浮选设备评述[J].选煤技术,2003.
[8]程宏志.振荡方法提高浮选选择性的研究[D].北京:中国矿业大学,2005.
[9]John Ralston,Daniel Fornasiero,Robert Hayes.Bubble-particle attachment and detachment in flotation[J].Int.J.Miner.Process.1999,56:133-164.
[10]卢寿慈.矿物浮选原理.北京:冶金工业出版社,1988.
[11]陈泉源,张泾生,王淀佐.气泡与颗粒研究新进展[J].国外金属矿选矿,2000(2):17-19.
[12]M.C.Fuerstenau.Flotation.A.M.Gaudin Memorial Volume.New York.1976,625-637.
[13]Anh V.Nguyen,Jhon Ralston,Hans Shulze.On modeling of bubble-particle attachment probability in flotation[J].Int.J.Miner.Process.1998,53:225-249.
[14]A.Nguyen Van.On the sliding time in flotation[J].Int.J.Miner.Process.1993,37:1-25.
[15]曾克文.浮选槽内矿浆紊流强度对浮选影响的理论及应用研究[D].湖南:中南大学,2001.
[16]胡熙庚等.浮选理论与工艺[M].长沙:中南工业大学出版社,1991.
[17]孙时元等.国外选矿设备手册(下)[M].冶金部马鞍山矿山研究院技术情报研究室,1990.
[18]Arbiter N.Flotation machines Froth Flotation[M].Fuersterstenau D W.edi.AIME,New York.1962,347.
[19]Harris C C.Impeller speed air and power requirements in flotation machine scale-up[J].Int J mineral processing,1974,(1):51.
[20]Harris C C.Flotation machine design and scale-up[J].mining magazing,1976,(9):207-213.
[21]Harris C C.Multiphase model of flotation machine bchariour[J].Int J mineral processing,1978,(5):107-129.
[22]Harris C C.Khandrika S M.Impeller/stator interactions a laboratory flotation machine:the effect of wear[J].Int J mineral processing,1984,(12):263-271.
[23]Harris C C.Khandrika S M.Flotation machine design:importart hydrodynamics effects slight geometric causes[J].Powder technology,1985,43(3):243-248.
[24]Harris C C.Khandrika S M.Flotation machine design:Impeller/stator interactions[J].Powder technology,1985a,43(3):273-278.
[25]Harris C C.Mensahbing R K.Acration characteristic of laboratory flotation machine impellers[J].Int J mineral processing,1977,(4):51-67.
[26]Harris C C.Rafa A.Flotation machine impeller speed and air rate as scale-up criteria[J].Tran inst mining and metellury,1970,(79):295.
[27]Degner V K.Hydrodynamic influences in flotation machine design[C].SME AIME annual meeting,New York:1985,24-28.
[28]Degner V R.Theveek H B.Large flotation cell design and development[J].Flotation AIME,New York:1976,(2):816.
[29]翟宏新译.浮选与浓缩[M].北京:机械工业出版社,1982.
[30]野中道郎等.浮选槽中的紊流变动速度及速度相关函数[J].选矿机械,1980,(4):28-37.
[31]野中道郎等.浮选槽中的紊流能及能量的传递[J].选矿机械,1982,(1):22-29.
[32]野中道郎等.浮选槽内气泡与微粒的冲撞[J].选矿机械,1982,(3):32-39.
[33]Schubert H,Bischofberger C.On the optimization of hydronamics in flotation processes proceeding[C].13~(th) Int miner process cong,Warszawa,1979,(2):1261 - 1257.
[34]任守正.利用激光测速仪研究浮选槽内流体动力学状态[D],北京:中国矿业大学,1982.
[35]吴江航,韩庆书.计算流体力学的理论、方法及应用[M],北京:科学出版社,1988.
[36]Tennekes.H,Lumley.J.L,AFirst Course in Turbulence,The MIT Press,Combridge,MA,1972.
[37]Gidaspow D,Multiphase Flow and Fluidization,Academic Press,San Diego,1994.
[38]Welch J E,Harlow F H,Shannon J Pet al,The MAC method:A computing technique for solving viscous,incompressible transient fluid problems involving free surface,Los Alamos Scientific Laboratory Report LA-3425,1966.
[39]Launder.B.E,Reece.G.J,Rodi.W,Progress in the Development of a Reynolds-Stress Turbulence Closure,Journal of Fluid Mechanics,1975,68(part3):537-56.
[40]周力行.湍流两相流与燃烧的数值模拟[M],北京:清华大学出版社,1991.
[41]Spalding D B,Computer simulation of two-phase flows,with special reference to nuclear-reactor systems,Computational Techniques in Heat Transfer,Prineridge Press,Swansea,1985,1-44.
[42]程宏志.机械搅拌式浮选机相似转换原理[J].煤炭学报,2000,25(增刊).
[43]崔广心.相似理论与模型试验[M].徐州:中国矿业大学出版社,1990.
[44]程宏志.充气速率和叶轮线速度对浮选效果的影响及机械搅拌式浮选机充气机理的探讨[D].徐州:中国矿业大学,1992.
[45]陈克成.流体力学实验技术[M].北京:机械工业出版社,1998.
[46]姚征.CFD通用软件综述[J].上海理工大学学报,2002(2).
[47]李勇.介绍流体力学通用软件-FLUENT[J].水动力学研究与进展,2001,16(2).
[48]叶大武.2006中国选煤和煤炭质量概述[J].选煤技术,2007(4).
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