中速磨煤机粗粉分离器分离特性数值模拟
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摘要
本文通过软件对火力发电厂中速磨煤机粗粉分离器的分离特性进行分析讨论,通过Catia建立三维模型,导入Gambit进行网格划分,利用Fluent进行模拟计算。结果表明:对于中速磨煤机径向粗粉分离器,相同挡板开度时,随着颗粒直径的增大,气体拽力逐渐减弱,颗粒重力影响逐渐加强,分离器分离作用逐渐加强。当颗粒直径不变时,随着挡板开度的增加,挡板阻力加大,气流旋流离心力增强,粗粉分离器的分离效率增加。取双R颗粒分布粒子进行五十度挡板开度不同风速颗粒追踪表明,该分离器处于10m/s时,分离器分离效果较好。通过对径向粗粉分离器的分析讨论,根据相关理论基础,提出径向改轴向的基本理论,并通过模拟分析进行数值对比得出在相同挡板开度情况下,轴向粗粉分离器的结构相对简单,没有中间内锥体,而且阻力较小,对于合格煤粉分离性能显著提高,减少了不必要的重复回粉,降低了能源消耗。设备磨损也低于径向型,提高了设备使用寿命。这些模拟数据的得出对于生产实践,以及日后可以开展的实验研究都有一定的积极作用。
With the development of national economy, energy source comes to be the chief issue. Saving and a reasonable use of the energy source is a main part of scientific development concept. Electric power should develop first in the development of economy; thus, many scholars pay their attention to research how to save the energy when developing electric power.
Mill separator is the main equipment in power station and other pulverized-coal systems of burning coal set, it has a huge influence on contribute and function of the mill. Classify efficiency and the size of coal powder at the export of the mill separator have an directly influence on the security, the stabilization and economy of the combustion in the hearth. It’s difficult to analyze the interior flow through experiment because of a complex equipment structure, a large energy consumption when operate, an actual larger interior size and high temperature of the boiler. So research flow and velocity character of mill separator through CFD simulation is feasible in this thesis.
In the past few decades,with the development of the calculation technique and the advance of the computer, computational fluid dynamics (CFD) has become more and more as a modern alternative for reducing the use of wind tunnels in automotive engineering. Now CFD is widely applied to various stages of aerodynamic design of automobiles. By contrast to the tunnel test, CFD is cheaper and takes less time to complete. However,the present CFD technology has still many problems to be solved for turbulence ,and it seems to be difficult to find an appropriate turbulence model to universal situations.
FlUENT software is used in this thesis to simulate several work conditions of classify character and flow character of the mill separator. The main work done as follows:
1 Analyzed the principium of radial classifier and read lots of literature on gas and liquid flow, chose a reasonable model, established a three-dimension model by CATIA software, plotted girding by guiding GAMBIT, researched the performance of radial classifier by single gas flow and gas-liquid double phrases flow separately. A k-epsilon onflow model was used in single gas flow research and a disperse model was used in gas-liquid double phrases flow research.
2 The result of single gas flow research for radial mill separator shows, gas has different velocity and angle when flowing different parts of radial tailing where the volume and the shape changes. The flow character and the swirl flow shape of axial interface and radial interface are clear to see. High flow velocity of integer flow field is come out in seldom areas. And high quality is needed in these areas, especially the damper where the velocity and press change acutely and get damaged easily. So maintenance is needed to guarantee the efficiency of mill separator.
3 The result of gas-liquid double phrases flow research for radial mill separator shows;Choose different degree of damper 35, 45, 55, the drag force of the gas is crucial when the particle is small in mill separator, the gravity and the resistance have little influence. The particle can go out of the exit of the mill separator easily with airflow. The gravity get strengthen when the diameter of the particle grows, and the drag force, the separation force, the gravity and the resistance act on the particle together, so it’s difficult to analyze the condition of the particle. One part of the particle flow with airflow, the other goes back to the exit of the mill separator. When the diameter of the particle keeps on grows, the drag force of the particle can’t generate separation force. The main force acted on the particle is the gravity and the resistance. Most of the particle is selected back to the pipe. A conclusion would make that with the diameter of the particle grows, the effect of drag force grows with a square multiple, and effect of the gravity grows with a cubic multiple. When the effect of drag force and effect of the gravity get close, the condition of the particle is most complex and the track of the particle is most difficult to analyze.
Choose the degree of damper is 50, the particle will be random classified by Rosin-Rammler. When the velocity of the airflow is slow, the efficiency of mill separator is lower, and a high velocity of the airflow will confuse the track of the particle, which will reduce the separation efficiency and make it difficult to analyze movement law of the particle.
4 Reconstruct radial mill separator to be axial mill separator rationally. Change the radial 16 leaves damper to 32 axial dampers. The result shows: The performance of mill separator improved, axial mill separator has a simple configuration, without centrum and the resistance are smaller, the unnecessary turn round coal powder reduced. So the separation performance of the coal powder is improved and the energy gets saved. The exit area of the mill separator is smaller than the entrance area, it's useful to enhance the flow velocity, and strengthen the following force of the airflow under the same condition. The velocity of the airflow is slower and the fray is smaller in axial mill separator, so axial mill separator gets a longer life.
With the development of national economy, energy source comes to be the chief issue. Saving and a reasonable use of the energy source is a main part of scientific development concept. Electric power should develop first in the development of economy; thus, many scholars pay their attention to research how to save the energy when developing electric power.
Mill separator is the main equipment in power station and other pulverized-coal systems of burning coal set, it has a huge influence on contribute and function of the mill. Classify efficiency and the size of coal powder at the export of the mill separator have an directly influence on the security, the stabilization and economy of the combustion in the hearth. It’s difficult to analyze the interior flow through experiment because of a complex equipment structure, a large energy consumption when operate, an actual larger interior size and high temperature of the boiler. So research flow and velocity character of mill separator through CFD simulation is feasible in this thesis.
In the past few decades,with the development of the calculation technique and the advance of the computer, computational fluid dynamics (CFD) has become more and more as a modern alternative for reducing the use of wind tunnels in automotive engineering. Now CFD is widely applied to various stages of aerodynamic design of automobiles. By contrast to the tunnel test, CFD is cheaper and takes less time to complete. However,the present CFD technology has still many problems to be solved for turbulence ,and it seems to be difficult to find an appropriate turbulence model to universal situations.
FlUENT software is used in this thesis to simulate several work conditions of classify character and flow character of the mill separator. The main work done as follows:
1 Analyzed the principium of radial classifier and read lots of literature on gas and liquid flow, chose a reasonable model, established a three-dimension model by CATIA software, plotted girding by guiding GAMBIT, researched the performance of radial classifier by single gas flow and gas-liquid double phrases flow separately. A k-epsilon onflow model was used in single gas flow research and a disperse model was used in gas-liquid double phrases flow research.
2 The result of single gas flow research for radial mill separator shows, gas has different velocity and angle when flowing different parts of radial tailing where the volume and the shape changes. The flow character and the swirl flow shape of axial interface and radial interface are clear to see. High flow velocity of integer flow field is come out in seldom areas. And high quality is needed in these areas, especially the damper where the velocity and press change acutely and get damaged easily. So maintenance is needed to guarantee the efficiency of mill separator.
3 The result of gas-liquid double phrases flow research for radial mill separator shows;Choose different degree of damper 35, 45, 55, the drag force of the gas is crucial when the particle is small in mill separator, the gravity and the resistance have little influence. The particle can go out of the exit of the mill separator easily with airflow. The gravity get strengthen when the diameter of the particle grows, and the drag force, the separation force, the gravity and the resistance act on the particle together, so it’s difficult to analyze the condition of the particle. One part of the particle flow with airflow, the other goes back to the exit of the mill separator. When the diameter of the particle keeps on grows, the drag force of the particle can’t generate separation force. The main force acted on the particle is the gravity and the resistance. Most of the particle is selected back to the pipe. A conclusion would make that with the diameter of the particle grows, the effect of drag force grows with a square multiple, and effect of the gravity grows with a cubic multiple. When the effect of drag force and effect of the gravity get close, the condition of the particle is most complex and the track of the particle is most difficult to analyze.
Choose the degree of damper is 50, the particle will be random classified by Rosin-Rammler. When the velocity of the airflow is slow, the efficiency of mill separator is lower, and a high velocity of the airflow will confuse the track of the particle, which will reduce the separation efficiency and make it difficult to analyze movement law of the particle.
4 Reconstruct radial mill separator to be axial mill separator rationally. Change the radial 16 leaves damper to 32 axial dampers. The result shows: The performance of mill separator improved, axial mill separator has a simple configuration, without centrum and the resistance are smaller, the unnecessary turn round coal powder reduced. So the separation performance of the coal powder is improved and the energy gets saved. The exit area of the mill separator is smaller than the entrance area, it's useful to enhance the flow velocity, and strengthen the following force of the airflow under the same condition. The velocity of the airflow is slower and the fray is smaller in axial mill separator, so axial mill separator gets a longer life.
引文
[1] 杨 菁,冯国勇。离心式可调煤粉分配器的研制和应用。华东电力试验研究院,200437
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[3] 胡荫平,贾鸿祥。新型煤粉燃烧器 [M]。西安 :西安交通大学出版社 ,1993.
[4] J.Kaulits and K.Roseberg,weiterentwicklung der Me—und Verfahrenstechnik sur Einstellung yon Steinkohlens—taufeuerungen , Forschung in der kraftwerkstechnik l998, VGB—Konferenz.Essen.
[5] 蒙尊谭。论电力在能源中的地位和作用。四川水力发电,1994,12:8~10
[6] 姜 武。煤粉分配器的使用现状及应用前景。江苏省电力设计院热机技术。2004.3
[7] 袁颖,赵仲瑰:我国劣质煤发电前景及预测。热力发电,1988(6),PP.I—10
[8] Strau(日),K. and Thelen, F.:Brennstoffaufbereitung als Beitrag zur Nox—Minderung. VGB KRAFTWERKSTECHNIK 69(1989).H. 2,S.2of —211
[9] Heitmuller,W.,and Schuster, H. : NOx 一 arme Kohlen- staub feuerungen and deren Komponenten. Babcock Mitteilunq Nr. 189,Stand:Friihjahr 1988.
[10] Albrecht,W.:Nox— Emissionen aus Kohlen- staubflammen. VGB KRAFTWERKSTECHNIK 72 (1992 ),H. 7, S. 614—621
[11] Schuler,U.,Stand der Mahltechnik in Kraftwerken. VGB KRAFTWERKSTECHNIK 70(1990),H. 7,5.577—595
[12] 孔文俊,程尚模,奕庆富。中速磨煤机粗粉分离器的现状与展望。
[13] 王国强。实用工程数值模拟技术及其在 ANSYS 上的实践。西安:西北工业大学出版社,1999
[14] Chorin, AJ Numerical solution of the Navier-Stokes equations Mathematics ofComputation 22,745~762
[15] 丁立新,王金枝,程新华等。电厂锅炉原理北京。中国电力出版社,2006
[16] 谭晓军,陈丽华。扩散式气固分离器内两相流动数值模拟。浙江大学机械与能源工程学院力学系,浙江杭州 310027
[17] 周云龙,高绥强,蔡辉,韩斌,史洪启,孙海天。可调式煤粉分配器煤粉分配特性的实验研。东北电力学院学。1998 - 09 - 28
[18] 史洪启等。双辽发电厂二号炉燃烧调整实验,科技报告。吉林电力科学研究院,1998
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[20] 岑可法等。工程气固多相流动理论及计算。浙江大学出版社,1990
[21] 徐明厚.一维炉高浓度煤粉实验研究.工程热物理学报,1992 ,(2)
[22] T Yokomine, A Shimizu, Prediction of turbulence modulation by using k-e model,Advances in Multiphase Flow, Elsevier Science, The Netherlands, 1995
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[28] 由长福,岳光溪。方型分离器内气固两相流动的数值模拟。工程热物理学报,1996,17(2):252～255
[29] 林文漪,何辉,周力行。工业油水分离器湍流两相流动的数值模拟。燃烧科学与技术,1995,1(4):287～291
[30] 邓兴勇。气固两相旋流分离流与旋流分离器的理论与实验研究:[博士学位论文]。上海:上海机械学院,1991.35～38
[31] 毛羽,庞磊,王小伟等。旋风分离器内三维紊流场的数值模拟。石油炼制与化工,2002,33(2):1～6
[32] 赵仲琥,张安国,王文元,梁辉。火力发电厂煤粉制备系统设计和计算方法。北京:中国电力出版社,1998
[33] Hideto Yoshida Three-dimensional simulation of air cyclone and particle separationby a revised-type cyclone Colloids and Surfaces A: Physicochemical and EngineeringAspects 109(1996) 1~12
[34] K Tuzla, JC Chen, Performance of a cyclone under high solid loadings, AICHE sympSer 88(289) (1992) 130-138
[35] W Batel, Dust Extraction: Technology Principle, Methods, Measurement Technique,Stonehouse Technicopy, England, 1976
[36] Li Xiaodong, Yan Jianhua, Cao Yuchun, Ni Mingjiang, Cen Kefa, Numericalsimulation of the effects of turbulence intensity and boundary layer on separationefficiency in a cyclone separator, Chemical Engineering Journal 95 (2003) 235-240
[37] 王海刚,刘石。不同湍流模型在旋风分离器三维数值模拟中的应用和比较。热能动力工程,18(4):337～343,2003
[38] ACHoffmann An experimental investigation elucidating the nature of the effect ofsolids loading on cyclone performance, Filtr Sep28(May 1991) 188~193
[39] LX Zhou, Theory and Numerical Modeling of Turbulent Gas-Particle Flows andCombustion, Science Press/CRC Press Inc, Boca Raton, 1993
[40] LX Zhou, SL Soo, Gas-solid flow and collection of solids in a cyclone separator,Powder Technol, 63(1990)45~53
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[2] 容銮恩。燃煤锅炉机组[M]。北京 :中国电力出版社,1998.
[3] 胡荫平,贾鸿祥。新型煤粉燃烧器 [M]。西安 :西安交通大学出版社 ,1993.
[4] J.Kaulits and K.Roseberg,weiterentwicklung der Me—und Verfahrenstechnik sur Einstellung yon Steinkohlens—taufeuerungen , Forschung in der kraftwerkstechnik l998, VGB—Konferenz.Essen.
[5] 蒙尊谭。论电力在能源中的地位和作用。四川水力发电,1994,12:8~10
[6] 姜 武。煤粉分配器的使用现状及应用前景。江苏省电力设计院热机技术。2004.3
[7] 袁颖,赵仲瑰:我国劣质煤发电前景及预测。热力发电,1988(6),PP.I—10
[8] Strau(日),K. and Thelen, F.:Brennstoffaufbereitung als Beitrag zur Nox—Minderung. VGB KRAFTWERKSTECHNIK 69(1989).H. 2,S.2of —211
[9] Heitmuller,W.,and Schuster, H. : NOx 一 arme Kohlen- staub feuerungen and deren Komponenten. Babcock Mitteilunq Nr. 189,Stand:Friihjahr 1988.
[10] Albrecht,W.:Nox— Emissionen aus Kohlen- staubflammen. VGB KRAFTWERKSTECHNIK 72 (1992 ),H. 7, S. 614—621
[11] Schuler,U.,Stand der Mahltechnik in Kraftwerken. VGB KRAFTWERKSTECHNIK 70(1990),H. 7,5.577—595
[12] 孔文俊,程尚模,奕庆富。中速磨煤机粗粉分离器的现状与展望。
[13] 王国强。实用工程数值模拟技术及其在 ANSYS 上的实践。西安:西北工业大学出版社,1999
[14] Chorin, AJ Numerical solution of the Navier-Stokes equations Mathematics ofComputation 22,745~762
[15] 丁立新,王金枝,程新华等。电厂锅炉原理北京。中国电力出版社,2006
[16] 谭晓军,陈丽华。扩散式气固分离器内两相流动数值模拟。浙江大学机械与能源工程学院力学系,浙江杭州 310027
[17] 周云龙,高绥强,蔡辉,韩斌,史洪启,孙海天。可调式煤粉分配器煤粉分配特性的实验研。东北电力学院学。1998 - 09 - 28
[18] 史洪启等。双辽发电厂二号炉燃烧调整实验,科技报告。吉林电力科学研究院,1998
[19] 苗长信.鳍片分离式浓淡燃烧器的开发与应用.热能动力工程,1997 ,(6)
[20] 岑可法等。工程气固多相流动理论及计算。浙江大学出版社,1990
[21] 徐明厚.一维炉高浓度煤粉实验研究.工程热物理学报,1992 ,(2)
[22] T Yokomine, A Shimizu, Prediction of turbulence modulation by using k-e model,Advances in Multiphase Flow, Elsevier Science, The Netherlands, 1995
[23] 倪浩清,沈永明。工程湍流流动、传热及传质的数值模拟。北京:中国水利电力出版社,1996
[24] Kim, J, Moin, P, Moser, R Turbulence statistics in fully developed channel flow at lowReynolds number Journal of Fluid Mechanics 177, 133~166
[25] Li, XL, Ma, YW, Fu, DX High efficient method for incompressible N-S equations andanalysis of two-dimensional turbulent channel flow Acta Mechanica Sinica 33(5),577~587
[26] 蔡兆林,吴克启,区颖达。离心风机叶轮内固粒运动轨迹及磨损量计算。华中理工大学学报,1996(2):105～110
[27] 蔡兆林。固粒对离心通风机叶轮撞击和磨损的分析。风机技术,1996(2):11～15
[28] 由长福,岳光溪。方型分离器内气固两相流动的数值模拟。工程热物理学报,1996,17(2):252～255
[29] 林文漪,何辉,周力行。工业油水分离器湍流两相流动的数值模拟。燃烧科学与技术,1995,1(4):287～291
[30] 邓兴勇。气固两相旋流分离流与旋流分离器的理论与实验研究:[博士学位论文]。上海:上海机械学院,1991.35～38
[31] 毛羽,庞磊,王小伟等。旋风分离器内三维紊流场的数值模拟。石油炼制与化工,2002,33(2):1～6
[32] 赵仲琥,张安国,王文元,梁辉。火力发电厂煤粉制备系统设计和计算方法。北京:中国电力出版社,1998
[33] Hideto Yoshida Three-dimensional simulation of air cyclone and particle separationby a revised-type cyclone Colloids and Surfaces A: Physicochemical and EngineeringAspects 109(1996) 1~12
[34] K Tuzla, JC Chen, Performance of a cyclone under high solid loadings, AICHE sympSer 88(289) (1992) 130-138
[35] W Batel, Dust Extraction: Technology Principle, Methods, Measurement Technique,Stonehouse Technicopy, England, 1976
[36] Li Xiaodong, Yan Jianhua, Cao Yuchun, Ni Mingjiang, Cen Kefa, Numericalsimulation of the effects of turbulence intensity and boundary layer on separationefficiency in a cyclone separator, Chemical Engineering Journal 95 (2003) 235-240
[37] 王海刚,刘石。不同湍流模型在旋风分离器三维数值模拟中的应用和比较。热能动力工程,18(4):337～343,2003
[38] ACHoffmann An experimental investigation elucidating the nature of the effect ofsolids loading on cyclone performance, Filtr Sep28(May 1991) 188~193
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