氧化沟流动特性的CFD模拟
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摘要
氧化沟工艺在目前水处理领域中应用广泛,表面曝气机是氧化沟工艺的核心动力设备,直接决定氧化沟处理污水的效率。数值模拟可以形象、准确地描述流体内部的流态分布,是水处理领域的一个新的研究方向。因此,本文运用FLUENT软件对氧化沟内水流的流场进行数值模拟,分析得出最优工况。
本文采用标准k -ε湍流模型和多重参考坐标系模型(MRF),并采用SIMPLEC算法,对32m(L)×8m(W)×4m(H)氧化沟内的流场进行三维数值模拟。根据工程实际对氧化沟内流场的要求,对比分析了在曝气机功率为12kW时氧化沟内的湍动能及流速场分布,得出最优工况。首先,对影响氧化沟流动特性的几个关键因素——表面曝气机叶片形状、叶片数目、曝气机浸深及曝气机附近弯道导流墙的半径进行单因素分析,得出当曝气机采用10叶片的机翼型叶片,曝气机浸深为0.5m,曝气机附近弯道导流墙半径为0.5m时表面曝气机对氧化沟内水流的混合推动力最大,为最优工况。其次,采用正交实验方法分析曝气机叶片形状、叶片数目、曝气机浸深及曝气机附近弯道导流墙半径对氧化沟断面及沟底平均流速的影响,通过对各因素进行方差和显著性分析,并考虑交互作用的影响得出:曝气机叶片形状和叶片数目是影响氧化沟断面及沟底平均流速的最为显著的因素。当曝气机采用10叶片的机翼型叶片,曝气机浸深为0.5m,曝气机附近弯道导流墙半径为0.5m时为最优组合。由多元线性回归得到氧化沟断面平均流速与各因素之间的线性关系为:y =0 .1637+0.01456x_1+0.1198x_2-0.00355x_3;氧化沟沟底平均流速与各因素之间的线性关系为:y =0 .06593+0.01121x_1+0.03275x_2+0.00195x_3。最后为了进一步对曝气机进行优化,本文对曝气机叶片的扭转角度进行优化分析,得出叶片扭转角度为20°时的流场最符合工程实际的要求。
本文运用数值模拟的方法计算分析了各因素对氧化沟流动特性的影响规律,较好的掌握了各因素在方案设计中的优先级别,对工程实践有着不可或缺的预测意义,避免较差工况的产生,节约能耗。
Oxidation ditch is widely used in wastewater treatment currently. Surface aerator is the core equipment in the oxidation ditch. It affects the efficiency of the oxidation ditch treating sewage directly. Numerical simulation is a new method of wastewater treatment research, because it can describe the flow field vividly and accurately. So the flow field of oxidation ditch was analyzed by FLUENT software in this article and the best working conditions were got.
The standard k ?εmodel and multiple reference frame model and SIMPLEC algorithm were used to simulate the 3-D numerical simulation of the flow field of a 32m(L)×8m(W)×4m (H) oxidation ditch. According to the engineering requirements, the distribution of turbulent kinetic energy and the velocity field of the oxidation ditch were analyzed to get the best working conditions when the surface aerator power is 12 kW. Firstly, the key factors of influencing the flow field of oxidation ditch such as the impeller blade shape and number of the surface aerator, the immersion depth of the surface aerator and the radius of guide wall near the surface aerator were analyzed, the results showed that the best working conditions and the largest mixed force were obtained when the impeller blade shape is airfoil , the number was 10, the immersion depth of the aerator was 0.5m, and the radius of guide wall near the aerator was 0.5m. Secondly, the average velocity of the section and the bottom of oxidation ditch were analyzed by orthogonal experiment, the results showed that the impeller blade shape and number of the surface aerator were the most significant factors. The optimal combination appeared when the impeller blade shape was airfoil, the blade number was 10, the immersion depth of the aerator was 0.5m and the radius of guide wall near the surface aerator was 0.5m. The linear relation of the average velocity of the section of the oxidation ditch with the factors was educed by multiple linear regression:y =0. 1637+0.01456x_1+0.1198x_2-0.00355x_3; The linear relation of the average velocity of the bottom of the oxidation ditch with the factors was educed by multiple linear regression:y =0 .06593+0.01121x_1+0.03275x_2+0.00195x_3. Finally, in order to optimize the surface aerator further, the reverse angles of the airfoil impeller blade were optimized designed, the result showed that the flow field fit the engineering requirements most when the reverse angles was 20.
By using the numerical simulation method, the flow characteristics of oxidation ditch were analyzed, and the priority of factors in the design was grasp better, the result had a significant forecast for the project, could avoid the poor working condition, and saving the energy consum- ption.
本文采用标准k -ε湍流模型和多重参考坐标系模型(MRF),并采用SIMPLEC算法,对32m(L)×8m(W)×4m(H)氧化沟内的流场进行三维数值模拟。根据工程实际对氧化沟内流场的要求,对比分析了在曝气机功率为12kW时氧化沟内的湍动能及流速场分布,得出最优工况。首先,对影响氧化沟流动特性的几个关键因素——表面曝气机叶片形状、叶片数目、曝气机浸深及曝气机附近弯道导流墙的半径进行单因素分析,得出当曝气机采用10叶片的机翼型叶片,曝气机浸深为0.5m,曝气机附近弯道导流墙半径为0.5m时表面曝气机对氧化沟内水流的混合推动力最大,为最优工况。其次,采用正交实验方法分析曝气机叶片形状、叶片数目、曝气机浸深及曝气机附近弯道导流墙半径对氧化沟断面及沟底平均流速的影响,通过对各因素进行方差和显著性分析,并考虑交互作用的影响得出:曝气机叶片形状和叶片数目是影响氧化沟断面及沟底平均流速的最为显著的因素。当曝气机采用10叶片的机翼型叶片,曝气机浸深为0.5m,曝气机附近弯道导流墙半径为0.5m时为最优组合。由多元线性回归得到氧化沟断面平均流速与各因素之间的线性关系为:y =0 .1637+0.01456x_1+0.1198x_2-0.00355x_3;氧化沟沟底平均流速与各因素之间的线性关系为:y =0 .06593+0.01121x_1+0.03275x_2+0.00195x_3。最后为了进一步对曝气机进行优化,本文对曝气机叶片的扭转角度进行优化分析,得出叶片扭转角度为20°时的流场最符合工程实际的要求。
本文运用数值模拟的方法计算分析了各因素对氧化沟流动特性的影响规律,较好的掌握了各因素在方案设计中的优先级别,对工程实践有着不可或缺的预测意义,避免较差工况的产生,节约能耗。
Oxidation ditch is widely used in wastewater treatment currently. Surface aerator is the core equipment in the oxidation ditch. It affects the efficiency of the oxidation ditch treating sewage directly. Numerical simulation is a new method of wastewater treatment research, because it can describe the flow field vividly and accurately. So the flow field of oxidation ditch was analyzed by FLUENT software in this article and the best working conditions were got.
The standard k ?εmodel and multiple reference frame model and SIMPLEC algorithm were used to simulate the 3-D numerical simulation of the flow field of a 32m(L)×8m(W)×4m (H) oxidation ditch. According to the engineering requirements, the distribution of turbulent kinetic energy and the velocity field of the oxidation ditch were analyzed to get the best working conditions when the surface aerator power is 12 kW. Firstly, the key factors of influencing the flow field of oxidation ditch such as the impeller blade shape and number of the surface aerator, the immersion depth of the surface aerator and the radius of guide wall near the surface aerator were analyzed, the results showed that the best working conditions and the largest mixed force were obtained when the impeller blade shape is airfoil , the number was 10, the immersion depth of the aerator was 0.5m, and the radius of guide wall near the aerator was 0.5m. Secondly, the average velocity of the section and the bottom of oxidation ditch were analyzed by orthogonal experiment, the results showed that the impeller blade shape and number of the surface aerator were the most significant factors. The optimal combination appeared when the impeller blade shape was airfoil, the blade number was 10, the immersion depth of the aerator was 0.5m and the radius of guide wall near the surface aerator was 0.5m. The linear relation of the average velocity of the section of the oxidation ditch with the factors was educed by multiple linear regression:y =0. 1637+0.01456x_1+0.1198x_2-0.00355x_3; The linear relation of the average velocity of the bottom of the oxidation ditch with the factors was educed by multiple linear regression:y =0 .06593+0.01121x_1+0.03275x_2+0.00195x_3. Finally, in order to optimize the surface aerator further, the reverse angles of the airfoil impeller blade were optimized designed, the result showed that the flow field fit the engineering requirements most when the reverse angles was 20.
By using the numerical simulation method, the flow characteristics of oxidation ditch were analyzed, and the priority of factors in the design was grasp better, the result had a significant forecast for the project, could avoid the poor working condition, and saving the energy consum- ption.
引文
[1]籍国东.我国污水资源化的现状分析与对策探讨[J].环境科学进展,1998(5):10.
[2]刘鸿亮,韩国刚,严济民等.中国水环境预测与对策概论[M].北京:中国环境科学出版社,1998:1-3.
[3]国家环保总局.2003年中国环境状况公报.2004.
[4]金兆丰,余志荣.污水处理组合工艺及工程实例[M].北京:化学工业出版社,2003:1.
[5]顾润南.我国城市生活污水处理方法述评[J].环境保护,2001 (9):46-47.
[6]王杉.对小城市污水处理工程设计的思考[J].给水排水,2003 (5):11.
[7] Baozhen Wang,Lin Wang and Luyu Yang,Case studies on pond eco-system for wastewater treatment and utilization in China,World marketing series,Global Water and Wastewater Technology,1999:64-71.
[8]王琳,杨鲁豫,王宝贞.我国城市污水处理的有效措施[J].城市环境与城市生态,2001第14卷1期:50-52.
[9]郑兴灿.我国城市污水处理的重点科技发展方向探讨[J].21世纪中国城市水管理国际研讨会.
[10]张自杰.排水工程[M].北京:中国建筑工业出版社,2000.
[11]王凯军,贾立敏.城市污水生物处理新技术开发与应用[M].北京:化学工业出版社,2001:226-320.
[12]罗麟,李伟民,邓荣森,等.一体化氧化沟的三维流场模拟与分析[J].中国给水排水,2003,19(12):15-18.
[13]张宗才,张新申,张铭让.氧化沟水力学分析及流场计算[J].中国皮革,2004,33 (11):22-25.
[14]张羽,黄卫东,勾全增,等.计算流体力学在氧化沟设计中的应用[J].工业用水与废水,2009,40(1):49-53.
[15]施慧明,刘艳臣,施汉昌,等.深水型表面曝气机的模拟计算与构型比较[J].环境工程学报,2008,2(2):154-159.
[16]陆豪,徐菲.Carrousel氧化沟转子水动力学特性研究.水利与建筑工程学报,2008,6(2):111-113.
[17] Stamou I. Modeling oxidation ditches using the IAWPRC activated sludge model with hydrodynamic effcts. Wat.Sci. Tech.,1994,30(2):185-192.
[18] Stamou I. Modeling of oxidation ditches using an open channel flow I-D advection– dispersion equation and ASM1 process description. Wat. Sci. Tech.,1997,36(5):269-276.
[19] Karama A B,Onyejekwe O.O, Brouckaert C.J.,Buckley C.A.,1999,The Use of Computational Fluid Dynamics(CFD),Technique for Evaluating,The Efficiency of An Activated Sludge Reactor[J].War.Sci.Tech.,39(10-11):329-332.
[20] De Clercq B.,Coen F.,Vanderhaegen B.,Vanrolleghem P.A.,(1999),Calibrating simple models for mixing and flow propagation in waste water treatment plants[J].Water Science and Technology,39(4):61-69.
[21] Simon S.,Roustan M.,Audic J.M.,Chatellier P.,200l,Prediction of mean circulation velocity in oxidation ditch[J].Environmental Technology,22(2):195-204.
[22] Pericleous K.A,Patel M.K 1987,The source-sink approach in the modeling of stirred reactors[J].Physico Chemical Hydrodynamics,9:279-297.
[23] Littleton H.X.and Daigger G.T.,2001,Application of computational fluid dynamics to closed loop bioreactors-Analysis of macro-environment variations in simultaneous biological nutrient removal systems[C].In:Proceedings of the Water Environment Federation 74th Annual Confefence&Exposition on Water Quality and Wastewater Treatment,Atlanta,GA,CD-ROM.
[24] Xu Y,McGrath G,1996,CFD prediction of stirred tank flows[J].Trans. Inst. Chem. Eng,74:471-475.
[25]王福军.计算流体动力学分析-CFD软件原理与应用[M].清华大学出版社,2004.
[26]周雪漪.计算水力学[M].北京:清华大学出版社,1995.
[27]陶文铨.数值传热学[M](第二版).西安:西安交通大学出版社,2001.
[28]郭鸿志.传输过程数值模拟.北京:冶金工业出版社,1998.
[29] H.K.Versteeg,W.Malalasekera.An Introduction to Computational Fluid Dynamis:The Finite Method.Wiley,New York,1995.
[30] B.E.Launder,D.B.Spalding,Lectures in Mathematical Models of Turbulence. Academic Press,London,1972.
[31]傅德熏,马延文.计算流体力学[M].北京:高等教育出版社,2002.
[32]侯拴第,张政,王英琛.搅拌槽三维流动场数值模拟[A].第九届化学工程科技报告会论文集[C].1998:583-587.
[33]王卫京.气液两相搅拌槽的数值模拟与实验研究[D].北京:中国科学院过程工程研究所,2002:15-20.
[34] S.V.Patanker,D.B.Spalding.A calculation pressure for heat,mass and momentum transfer in three-dimensional parabolic flows[J].Int J Heat Mass Transfer,1972,15:1787-1806.
[35] Launder B E,Spalding D B. The numerical computation of turbulent flows[J]. Computer Methods in Applied Mechanics and Engineering,1994,(3):269-289.
[36] Gao Shouyou,Peng Yongzhen,Wang Shuying,et al. Novel strategy of nitrogen removal from domestic wastewater using pilot Orbal oxidation ditch[J].Journal of Environmental Sciences,2006,18(5):833-839.
[37] Peng Yongzhen,Hou Hongxun,Wang Shuying,et al. Nitrogen and phosphorus removal in pilot-scale anaerobic-anoxic oxidation ditch system[J]. Journal of Environmental Sciences.2008,20(4):398-403.
[38] Liu Yanchen,Shi Hanchang,Xia Lan,et al. Study of operational conditions of simultaneous nitrification and denitrifi- cation in a Carrousel oxidation ditch for domestic wastewater treatment[J]. Bioresource Technology.2010,101(3):901-906.
[39] Liu Yanchen,Shi Hanchang,Shi Hui ming,et al. Study on a discrete-time dynamic control model to enhance nitrogen removal with fluctuation of influent in oxidation ditches[J].Water Research,2010,44(18):5150-5157.
[40] Lei Ge,Ren Hongqiang,Ding Lili,et al. A full-scale biological treatment system application in the treated wastewater of pharmaceutical industrial park[J]. Bio- resource Technology,2010,101(15):5852-5861.
[41]杨华展等.一体化氧化沟弯道流态特性研究[J].重庆建筑大学学报,2001,29(3):106-114.
[42] R.K.Islamgaliev,R.Kuzel,S.N.Mikov,et a1.Mater Sci Eng A,1998,249:152.
[43]中国科学院数学研究所数理统计组,正交试验法,北京:人民教育出版社,1975.
[2]刘鸿亮,韩国刚,严济民等.中国水环境预测与对策概论[M].北京:中国环境科学出版社,1998:1-3.
[3]国家环保总局.2003年中国环境状况公报.2004.
[4]金兆丰,余志荣.污水处理组合工艺及工程实例[M].北京:化学工业出版社,2003:1.
[5]顾润南.我国城市生活污水处理方法述评[J].环境保护,2001 (9):46-47.
[6]王杉.对小城市污水处理工程设计的思考[J].给水排水,2003 (5):11.
[7] Baozhen Wang,Lin Wang and Luyu Yang,Case studies on pond eco-system for wastewater treatment and utilization in China,World marketing series,Global Water and Wastewater Technology,1999:64-71.
[8]王琳,杨鲁豫,王宝贞.我国城市污水处理的有效措施[J].城市环境与城市生态,2001第14卷1期:50-52.
[9]郑兴灿.我国城市污水处理的重点科技发展方向探讨[J].21世纪中国城市水管理国际研讨会.
[10]张自杰.排水工程[M].北京:中国建筑工业出版社,2000.
[11]王凯军,贾立敏.城市污水生物处理新技术开发与应用[M].北京:化学工业出版社,2001:226-320.
[12]罗麟,李伟民,邓荣森,等.一体化氧化沟的三维流场模拟与分析[J].中国给水排水,2003,19(12):15-18.
[13]张宗才,张新申,张铭让.氧化沟水力学分析及流场计算[J].中国皮革,2004,33 (11):22-25.
[14]张羽,黄卫东,勾全增,等.计算流体力学在氧化沟设计中的应用[J].工业用水与废水,2009,40(1):49-53.
[15]施慧明,刘艳臣,施汉昌,等.深水型表面曝气机的模拟计算与构型比较[J].环境工程学报,2008,2(2):154-159.
[16]陆豪,徐菲.Carrousel氧化沟转子水动力学特性研究.水利与建筑工程学报,2008,6(2):111-113.
[17] Stamou I. Modeling oxidation ditches using the IAWPRC activated sludge model with hydrodynamic effcts. Wat.Sci. Tech.,1994,30(2):185-192.
[18] Stamou I. Modeling of oxidation ditches using an open channel flow I-D advection– dispersion equation and ASM1 process description. Wat. Sci. Tech.,1997,36(5):269-276.
[19] Karama A B,Onyejekwe O.O, Brouckaert C.J.,Buckley C.A.,1999,The Use of Computational Fluid Dynamics(CFD),Technique for Evaluating,The Efficiency of An Activated Sludge Reactor[J].War.Sci.Tech.,39(10-11):329-332.
[20] De Clercq B.,Coen F.,Vanderhaegen B.,Vanrolleghem P.A.,(1999),Calibrating simple models for mixing and flow propagation in waste water treatment plants[J].Water Science and Technology,39(4):61-69.
[21] Simon S.,Roustan M.,Audic J.M.,Chatellier P.,200l,Prediction of mean circulation velocity in oxidation ditch[J].Environmental Technology,22(2):195-204.
[22] Pericleous K.A,Patel M.K 1987,The source-sink approach in the modeling of stirred reactors[J].Physico Chemical Hydrodynamics,9:279-297.
[23] Littleton H.X.and Daigger G.T.,2001,Application of computational fluid dynamics to closed loop bioreactors-Analysis of macro-environment variations in simultaneous biological nutrient removal systems[C].In:Proceedings of the Water Environment Federation 74th Annual Confefence&Exposition on Water Quality and Wastewater Treatment,Atlanta,GA,CD-ROM.
[24] Xu Y,McGrath G,1996,CFD prediction of stirred tank flows[J].Trans. Inst. Chem. Eng,74:471-475.
[25]王福军.计算流体动力学分析-CFD软件原理与应用[M].清华大学出版社,2004.
[26]周雪漪.计算水力学[M].北京:清华大学出版社,1995.
[27]陶文铨.数值传热学[M](第二版).西安:西安交通大学出版社,2001.
[28]郭鸿志.传输过程数值模拟.北京:冶金工业出版社,1998.
[29] H.K.Versteeg,W.Malalasekera.An Introduction to Computational Fluid Dynamis:The Finite Method.Wiley,New York,1995.
[30] B.E.Launder,D.B.Spalding,Lectures in Mathematical Models of Turbulence. Academic Press,London,1972.
[31]傅德熏,马延文.计算流体力学[M].北京:高等教育出版社,2002.
[32]侯拴第,张政,王英琛.搅拌槽三维流动场数值模拟[A].第九届化学工程科技报告会论文集[C].1998:583-587.
[33]王卫京.气液两相搅拌槽的数值模拟与实验研究[D].北京:中国科学院过程工程研究所,2002:15-20.
[34] S.V.Patanker,D.B.Spalding.A calculation pressure for heat,mass and momentum transfer in three-dimensional parabolic flows[J].Int J Heat Mass Transfer,1972,15:1787-1806.
[35] Launder B E,Spalding D B. The numerical computation of turbulent flows[J]. Computer Methods in Applied Mechanics and Engineering,1994,(3):269-289.
[36] Gao Shouyou,Peng Yongzhen,Wang Shuying,et al. Novel strategy of nitrogen removal from domestic wastewater using pilot Orbal oxidation ditch[J].Journal of Environmental Sciences,2006,18(5):833-839.
[37] Peng Yongzhen,Hou Hongxun,Wang Shuying,et al. Nitrogen and phosphorus removal in pilot-scale anaerobic-anoxic oxidation ditch system[J]. Journal of Environmental Sciences.2008,20(4):398-403.
[38] Liu Yanchen,Shi Hanchang,Xia Lan,et al. Study of operational conditions of simultaneous nitrification and denitrifi- cation in a Carrousel oxidation ditch for domestic wastewater treatment[J]. Bioresource Technology.2010,101(3):901-906.
[39] Liu Yanchen,Shi Hanchang,Shi Hui ming,et al. Study on a discrete-time dynamic control model to enhance nitrogen removal with fluctuation of influent in oxidation ditches[J].Water Research,2010,44(18):5150-5157.
[40] Lei Ge,Ren Hongqiang,Ding Lili,et al. A full-scale biological treatment system application in the treated wastewater of pharmaceutical industrial park[J]. Bio- resource Technology,2010,101(15):5852-5861.
[41]杨华展等.一体化氧化沟弯道流态特性研究[J].重庆建筑大学学报,2001,29(3):106-114.
[42] R.K.Islamgaliev,R.Kuzel,S.N.Mikov,et a1.Mater Sci Eng A,1998,249:152.
[43]中国科学院数学研究所数理统计组,正交试验法,北京:人民教育出版社,1975.