CFB锅炉旋风分离器内气固两相流动的数值模拟
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摘要
旋风分离器作为循环流化床锅炉中重要的气固分离设备,其性能的好坏直接影响到整个循环流化床锅炉的出力、效率及运行寿命。为了使该设备更好地服务于生产实际,本文采用商用CFD软件FLUENT对直切式旋风分离器内的气相流场进行了数值研究。结果表明:雷诺应力湍流模型对气相流场的计算与实验测量结果基本相符,有较高的预报精度;旋风分离器入口结构的非轴对性以及气相旋流的不稳定性造成气相流场呈非轴对称性,主要表现为气流旋转中心与分离器几何中心不重合;排气管内切向速度呈强旋流状态,轴向速度呈强剪切流特征,这些都是造成排气管内产生流动阻力的重要原因。同时还研究了入口面积比K A、排气管直径比d~r、排尘口直径比d~c、入口速度Vi和温度T等结构参数和操作条件对气相流场的影响规律,为旋风分离器的结构优化提供了参考依据。最后,在气相流场模拟的基础上,引入颗粒随机轨道模型,计算了颗粒的运动轨迹。结果表明,分离器内颗粒的运动情况非常复杂,并且带有很大的随机性。对于细小颗粒,上行流夹带是影响效率的主要因素,其次是短路流和排尘口返混;对于粒径较大的颗粒,影响效率的主要因素是顶灰环和排气管短路流。以上研究结果对于旋风分离器分离机理的研究具有一定的参考价值。
The cyclone separator is one of the most important components in CFB boilers. Its efficiency is vital for the proper operation of the boiler. In order to make the equipment serve the industry better, the gas-phase flow filed in the cyclone separator was numerical studied by using the commercial software FLUENT. The simulation results based on the Reynolds stress model are in good agreement with the measured results. The results show that the gas flow filed is asymmetric due to the asymmetry of the inlet structure and the unstable characteristics of the swirl flow, and the vortex center of the gas flow is deviated from the geometrical center of the cyclone; the high gas swirling intensity and shear flow characteristics of the axial velocity in the vortex finder are contributed to the energy loss. Besides, the effects of the structural parameters and operating conditions on the gas phase flow were studied to provide references for the design and operation of cyclone separator, including the area ratio of cyclone cross-section to inlet section (KA), the diameter ratio of the vortex finder to the cyclone ( d~r ), the diameter ratio of the dust discharge to the cyclone ( d~c ), inlet velocity ( Vi ) and temperature (T). Finally, on the basis of the gas flow field, solid particle trajectories were simulated by using the two-way coupling lagrangian scheme. The results show that particle motion is very complex and has a great randomness. For the fine particles, the main factors influencing the efficiency are the air entrainment in the inner vortex region, short-circuit flow near the vortex head and re-entrainment at the bottom of discharge cone. For the larger particles, the main influencing factors are“upper dust ring”near the top plate and short-circuit flow near the vortex head. The above results have a certain reference value for the research on the separation mechanism of cyclone separator.
The cyclone separator is one of the most important components in CFB boilers. Its efficiency is vital for the proper operation of the boiler. In order to make the equipment serve the industry better, the gas-phase flow filed in the cyclone separator was numerical studied by using the commercial software FLUENT. The simulation results based on the Reynolds stress model are in good agreement with the measured results. The results show that the gas flow filed is asymmetric due to the asymmetry of the inlet structure and the unstable characteristics of the swirl flow, and the vortex center of the gas flow is deviated from the geometrical center of the cyclone; the high gas swirling intensity and shear flow characteristics of the axial velocity in the vortex finder are contributed to the energy loss. Besides, the effects of the structural parameters and operating conditions on the gas phase flow were studied to provide references for the design and operation of cyclone separator, including the area ratio of cyclone cross-section to inlet section (KA), the diameter ratio of the vortex finder to the cyclone ( d~r ), the diameter ratio of the dust discharge to the cyclone ( d~c ), inlet velocity ( Vi ) and temperature (T). Finally, on the basis of the gas flow field, solid particle trajectories were simulated by using the two-way coupling lagrangian scheme. The results show that particle motion is very complex and has a great randomness. For the fine particles, the main factors influencing the efficiency are the air entrainment in the inner vortex region, short-circuit flow near the vortex head and re-entrainment at the bottom of discharge cone. For the larger particles, the main influencing factors are“upper dust ring”near the top plate and short-circuit flow near the vortex head. The above results have a certain reference value for the research on the separation mechanism of cyclone separator.
引文
[1]林宗虎,魏敦崧,安恩科,等.循环流化床锅炉[M] .北京:化学工业出版社,2004:2-3,68-69
[2] P.巴苏,S.A弗雷泽.循环流化床锅炉的设计与运行[M] .北京:科学出版社,1994:8-12
[3]岑可法,倪明江,骆仲泱,等.循环流化床锅炉理论、设计与运行[M].北京:中国电力出版社,1998:10-12,494-495
[4]李军,刘汉周,卢啸风.循环流化床锅炉旋风分离器的最新进展[J] .能源研究与信息,2004,20(2):74-78
[5]陈汉平.循环流化床气固分离的理论与应用[D] .武汉:华中理工大学,2000
[6]周强.方形卧式分离器的研究及其在循环流化床锅炉中的应用[D] .杭州:浙江大学,2004
[7]张昌建,袁文山,赵辉,等.循环流化床锅炉的发展及前景[J] .河北建筑科技学院学报,2004,21(1):81-83
[8]陈汉平,林志杰,黄琳,等.循环流化床锅炉飞灰分离器[P].中国专利:911003649,1991
[9]岑可法,倪明江,骆仲泱,等.方形下排气热交换分离器[P] .中国专利:ZL94223276.3,1994
[10] Boysan F., Ayers W. H., Swithenbank J. A fundamental mathematical modeling approach to cyclone design[J] . Transaction of the Institution of Chemical Engineers, 1982,60: 222-230
[11] Zhou L. X., Soo S. L. Gas-solid flow and collection of solids in cyclone separator[J] . Powder Technology, 1990,63: 45-53
[12] Griffiths W. D., Boysan F. Computational fluid dynamics (CFD) and empirical modeling of the performance of a number of cyclone samplers[J] . Journal of Aerosol Science, 1996, 27(2):281-304
[13] Ma L., Ingham D. B., Wen X. Numerical modeling of the fluid and particle penetration through small sampling cyclones[J]. Journal of Aerosol Science 2000, 31(9):1097-1119
[14] Hoekstra A. J., Deksen J. J., Van Den Akker H. E. A. An experimental and numericalstudy of turbulent swirling flow in gas cyclones[J]. Chemical Engineering Science, 1999, 54:2055-2065
[15] Derksen J. J., Van Den Akker H. E. A. Simulation of vortex core precession in a reverse-flow cyclone[J] . AICHE Journal, 2000, 46(7): 1117-1331
[16]吴小林,申屠进华,姬忠礼.PV型旋风分离器内三维流场的数值模拟[J] .石油学报(石油加工),2003,19(5):74-79
[17]吴小林,熊志宜,姬忠礼,等.旋风分离器旋进涡核的数值模拟[J] .化工学报,2007,58(2):383-390
[18] Gimbun J., Chuah T.G., Fakhru’l-Razi A., et al. The Influence of Temperature and Inlet Velocity on Cyclone Drop: a CFD Study[J] . Chemical Engineering and Processing. 2005, 44:7-12
[19]胡砾元,时铭显,周力行,等.旋风分离器三维强旋湍流流动的数值模拟[J].清华大学学报(自然科学版),2004,44(11):1501-1504
[20]胡砾元,周力行,时铭显,等.旋风分离器三维强旋湍流流动数值模拟的修正压力应变项模型[J].工程力学,2005,22(5):83-88
[21] Hu L.Y., Zhou L.X., Zhang J., Studies on strongly swirling flows in the full space of a volute cyclone separator[J]. AIChE Journal, 2005,51(3): 740-749
[22]刘成文.旋风分离器的能耗与减阻杆减阻机理研究[D] .北京:清华大学,2006,
[23]周立行.湍流两相流动与燃烧的数值模拟[M] .北京:清华大学出版社,1991:81-82,135-144
[24]吴小林,时铭显.旋风分离器内颗粒运动规律的数值模拟[J] .化工机械,1994,21(6):333-337
[25]胡砾元,吴小林,时铭显.旋风分离器内颗粒轨迹的计算方法[J].石油大学学报(自然科学版),1998,22(4):64-67
[26]吴飞雪,吴小林,时铭显.PV型旋风分离器内颗粒轨迹计算的初步探讨[J] .石油化工设备技术,1998,19(2):14-17
[27]王博.旋风分离器内气固两相运动的数值仿真研究[D] .西安:西安建筑科技大学,2003
[28]王海刚.旋风分离器中气-固两相流数值计算与实验研究[D] .北京:中国科学院工程热物理研究所,2003
[29] Derksen J.J., Separation performance predictions of a stairmand high-efficiency cyclone[J]. AICHE Journal, 2003, 49(6): 1359-1371
[30] Derksen J.J., Sundaresan S., Van Den Akker H.E.A., Simulation of mass-loading effects in gas-solid cyclone separators[J]. Powder Technology, 2006(163): 59-68
[31]薛晓虎.旋风分离器全空间内气固两相流动特性的分析[D] .北京:中国石油大学,2005
[32] Xue X. H., Sun G. G., Wan G. J., et al. Numerical simulation of particle concentration in a gas cyclone separator[J]. Petroleum science. 2007, 4(3): 76-83
[33]陶文铨.数值传热学[M].西安:西安交通大学出版社,2001:337-338,353-359
[34] Fluent Inc . Fluent 6.2 User’s Guide. Fluent Inc,2005
[35]王福军.计算流体动力学分析——CFD软件原理与应用[M] .北京:清华大学出版社,2004:215-216
[36]姬忠礼,时铭显.旋风分离器内流场的测试技术[J].石油大学学报(自然科学版),1991,15(6):52-58
[37] A.C.霍夫曼,L.E.斯坦因.旋风分离器——原理、设计和工程应用[M] .北京:化学工业出版社,2004:31-32
[38]钱付平,章名耀.不同排尘结构旋风分离器的分离特性[J] .燃烧科学与技术,2006,12(2):169-174
[39]王建军,王连泽,刘成文.旋风分离器排气管内流动分析及减阻机理[J] .过程工程学报,2005,15(3):251-254
[40]宋健斐,魏耀东,时铭显.蜗壳式旋风分离器内气相流场非轴对称性分析[J] .化工学报,2007,58(5):1091-1096
[41]孔行健,孙国刚,刘长征,等.芯管半切旋风分离器的实验研究[J].中国粉体技术,2004,第10卷专辑(第七届全国颗粒制备与处理学术和应用研讨会),96-99
[42]沈恒根,党义荣,刁永发,等.双进口旋风器内流场的实验研究[J] .西安建筑科技大学学报,1997,29(3):275-277
[43]宋贤良,朱利,李永胜,等.轴对称进口旋风分离器性能的研究[J] .郑州工程学院学报,2000,21(4):34-40
[44]宋健斐,魏耀东,时铭显.蜗壳式旋风分离器内气相流场非轴对称特性的模拟[J].化工学报,2005,56(8):1397-1402
[45]时铭显.旋风分离技术与设备研究成果与论文选集[M] .北京:石油大学,1995:6-7
[46] Chen J. Y, Shi M. X. A universal model to calculate cyclone pressure drop[J] . Powder technology, 2007, 171: 184-191
[47]许世森,许晋源.温度和压力对旋风分离器高温除尘性能影响的研究[J] .动力工程,1997,17(2):52-58
[48] Chen J. Y. Shi M. X, Analysis on cyclone collection efficiencies at high temperatures[J], China Particulogy, 2003, 1(1):20-26
[49]李文琦,陈建义.旋风分离器高温性能试验研究[J].中国石油大学学报(自然科学版),2006,30(3):97-100
[50] Shin M. S.,Kim H. S.,Jang D. S. A numerical and experimental study on a high efficiency cyclone dust separator for high temperature and pressurized environments[J]. Applied Thermal Engineering. 2005,25(12): 1821-1835
[51]钱付平,章名耀.温度对旋风分离器分离性能影响的数值研究[J] .动力工程,2006,26(2):253-257
[52]万古军,魏耀东,时铭显.高温条件下旋风分离器内气相流场的数值模拟[J] .过程工程学报.2007,7(5):871-876
[53] Shi L.M.,Bayless D. J. Comparison of boundary conditions for predicting the collection efficiency of cyclones[J] . Powder Technology. 2007, 173: 29-37
[2] P.巴苏,S.A弗雷泽.循环流化床锅炉的设计与运行[M] .北京:科学出版社,1994:8-12
[3]岑可法,倪明江,骆仲泱,等.循环流化床锅炉理论、设计与运行[M].北京:中国电力出版社,1998:10-12,494-495
[4]李军,刘汉周,卢啸风.循环流化床锅炉旋风分离器的最新进展[J] .能源研究与信息,2004,20(2):74-78
[5]陈汉平.循环流化床气固分离的理论与应用[D] .武汉:华中理工大学,2000
[6]周强.方形卧式分离器的研究及其在循环流化床锅炉中的应用[D] .杭州:浙江大学,2004
[7]张昌建,袁文山,赵辉,等.循环流化床锅炉的发展及前景[J] .河北建筑科技学院学报,2004,21(1):81-83
[8]陈汉平,林志杰,黄琳,等.循环流化床锅炉飞灰分离器[P].中国专利:911003649,1991
[9]岑可法,倪明江,骆仲泱,等.方形下排气热交换分离器[P] .中国专利:ZL94223276.3,1994
[10] Boysan F., Ayers W. H., Swithenbank J. A fundamental mathematical modeling approach to cyclone design[J] . Transaction of the Institution of Chemical Engineers, 1982,60: 222-230
[11] Zhou L. X., Soo S. L. Gas-solid flow and collection of solids in cyclone separator[J] . Powder Technology, 1990,63: 45-53
[12] Griffiths W. D., Boysan F. Computational fluid dynamics (CFD) and empirical modeling of the performance of a number of cyclone samplers[J] . Journal of Aerosol Science, 1996, 27(2):281-304
[13] Ma L., Ingham D. B., Wen X. Numerical modeling of the fluid and particle penetration through small sampling cyclones[J]. Journal of Aerosol Science 2000, 31(9):1097-1119
[14] Hoekstra A. J., Deksen J. J., Van Den Akker H. E. A. An experimental and numericalstudy of turbulent swirling flow in gas cyclones[J]. Chemical Engineering Science, 1999, 54:2055-2065
[15] Derksen J. J., Van Den Akker H. E. A. Simulation of vortex core precession in a reverse-flow cyclone[J] . AICHE Journal, 2000, 46(7): 1117-1331
[16]吴小林,申屠进华,姬忠礼.PV型旋风分离器内三维流场的数值模拟[J] .石油学报(石油加工),2003,19(5):74-79
[17]吴小林,熊志宜,姬忠礼,等.旋风分离器旋进涡核的数值模拟[J] .化工学报,2007,58(2):383-390
[18] Gimbun J., Chuah T.G., Fakhru’l-Razi A., et al. The Influence of Temperature and Inlet Velocity on Cyclone Drop: a CFD Study[J] . Chemical Engineering and Processing. 2005, 44:7-12
[19]胡砾元,时铭显,周力行,等.旋风分离器三维强旋湍流流动的数值模拟[J].清华大学学报(自然科学版),2004,44(11):1501-1504
[20]胡砾元,周力行,时铭显,等.旋风分离器三维强旋湍流流动数值模拟的修正压力应变项模型[J].工程力学,2005,22(5):83-88
[21] Hu L.Y., Zhou L.X., Zhang J., Studies on strongly swirling flows in the full space of a volute cyclone separator[J]. AIChE Journal, 2005,51(3): 740-749
[22]刘成文.旋风分离器的能耗与减阻杆减阻机理研究[D] .北京:清华大学,2006,
[23]周立行.湍流两相流动与燃烧的数值模拟[M] .北京:清华大学出版社,1991:81-82,135-144
[24]吴小林,时铭显.旋风分离器内颗粒运动规律的数值模拟[J] .化工机械,1994,21(6):333-337
[25]胡砾元,吴小林,时铭显.旋风分离器内颗粒轨迹的计算方法[J].石油大学学报(自然科学版),1998,22(4):64-67
[26]吴飞雪,吴小林,时铭显.PV型旋风分离器内颗粒轨迹计算的初步探讨[J] .石油化工设备技术,1998,19(2):14-17
[27]王博.旋风分离器内气固两相运动的数值仿真研究[D] .西安:西安建筑科技大学,2003
[28]王海刚.旋风分离器中气-固两相流数值计算与实验研究[D] .北京:中国科学院工程热物理研究所,2003
[29] Derksen J.J., Separation performance predictions of a stairmand high-efficiency cyclone[J]. AICHE Journal, 2003, 49(6): 1359-1371
[30] Derksen J.J., Sundaresan S., Van Den Akker H.E.A., Simulation of mass-loading effects in gas-solid cyclone separators[J]. Powder Technology, 2006(163): 59-68
[31]薛晓虎.旋风分离器全空间内气固两相流动特性的分析[D] .北京:中国石油大学,2005
[32] Xue X. H., Sun G. G., Wan G. J., et al. Numerical simulation of particle concentration in a gas cyclone separator[J]. Petroleum science. 2007, 4(3): 76-83
[33]陶文铨.数值传热学[M].西安:西安交通大学出版社,2001:337-338,353-359
[34] Fluent Inc . Fluent 6.2 User’s Guide. Fluent Inc,2005
[35]王福军.计算流体动力学分析——CFD软件原理与应用[M] .北京:清华大学出版社,2004:215-216
[36]姬忠礼,时铭显.旋风分离器内流场的测试技术[J].石油大学学报(自然科学版),1991,15(6):52-58
[37] A.C.霍夫曼,L.E.斯坦因.旋风分离器——原理、设计和工程应用[M] .北京:化学工业出版社,2004:31-32
[38]钱付平,章名耀.不同排尘结构旋风分离器的分离特性[J] .燃烧科学与技术,2006,12(2):169-174
[39]王建军,王连泽,刘成文.旋风分离器排气管内流动分析及减阻机理[J] .过程工程学报,2005,15(3):251-254
[40]宋健斐,魏耀东,时铭显.蜗壳式旋风分离器内气相流场非轴对称性分析[J] .化工学报,2007,58(5):1091-1096
[41]孔行健,孙国刚,刘长征,等.芯管半切旋风分离器的实验研究[J].中国粉体技术,2004,第10卷专辑(第七届全国颗粒制备与处理学术和应用研讨会),96-99
[42]沈恒根,党义荣,刁永发,等.双进口旋风器内流场的实验研究[J] .西安建筑科技大学学报,1997,29(3):275-277
[43]宋贤良,朱利,李永胜,等.轴对称进口旋风分离器性能的研究[J] .郑州工程学院学报,2000,21(4):34-40
[44]宋健斐,魏耀东,时铭显.蜗壳式旋风分离器内气相流场非轴对称特性的模拟[J].化工学报,2005,56(8):1397-1402
[45]时铭显.旋风分离技术与设备研究成果与论文选集[M] .北京:石油大学,1995:6-7
[46] Chen J. Y, Shi M. X. A universal model to calculate cyclone pressure drop[J] . Powder technology, 2007, 171: 184-191
[47]许世森,许晋源.温度和压力对旋风分离器高温除尘性能影响的研究[J] .动力工程,1997,17(2):52-58
[48] Chen J. Y. Shi M. X, Analysis on cyclone collection efficiencies at high temperatures[J], China Particulogy, 2003, 1(1):20-26
[49]李文琦,陈建义.旋风分离器高温性能试验研究[J].中国石油大学学报(自然科学版),2006,30(3):97-100
[50] Shin M. S.,Kim H. S.,Jang D. S. A numerical and experimental study on a high efficiency cyclone dust separator for high temperature and pressurized environments[J]. Applied Thermal Engineering. 2005,25(12): 1821-1835
[51]钱付平,章名耀.温度对旋风分离器分离性能影响的数值研究[J] .动力工程,2006,26(2):253-257
[52]万古军,魏耀东,时铭显.高温条件下旋风分离器内气相流场的数值模拟[J] .过程工程学报.2007,7(5):871-876
[53] Shi L.M.,Bayless D. J. Comparison of boundary conditions for predicting the collection efficiency of cyclones[J] . Powder Technology. 2007, 173: 29-37