Flow and mixing characteristics in willow leaf-like static mixer

doi:10.11949/j.issn.0438-1157.20170755

Abstract

Abstract:

Gas mixing flow in willow leaf-like static mixer was studied on both velocity and concentration field. The experimental results showed that deviations of velocity and concentration fields were reached to ideal range and were better than those of national standards. CFD simulation on the mixer flow field exhibited good consistencies in numerical values and distribution of concentration cloud diagram between experiment and simulation. Subsequent studies showed that mixing was promoted by longitudinal and hairpin vortices appeared in tailing wake zone of the mixing element. When gas was passing through the mixing element, a high turbulent flow energy dissipation region formed by turbulence-induced increase of kinetic energy dissipation rate could drive much frequent material transfer. Flow resistance of the entire static mixer also occurred mainly in this high energy dissipation region. To some extent, back mixing after the high energy dissipation region strengthened mixing effect.

Key words: willow leaf-like, airflow back mixing, flow mixing characteristics, mixing, static mixer

摘要：

对仿柳叶形静态混合器内混合气流进行了速度场与浓度场的试验研究，结果表明该混合器内速度场与浓度场偏差均达到了非常理想的效果（优于国家标准偏差值）。同时采用CFD软件对该静态混合器内的流场进行了数值模拟，试验与模拟的数值结果以及两者的浓度云图分布都有着较好的一致性。随后的研究结果表明：在混合元件尾迹区域出现了纵向涡和发卡涡来促进混合；在经过混合元件区域时因为湍流动能耗散率增加形成的高湍流动能耗散率区能够使物质交换更加频繁；整个静态混合器的流动阻力也主要发生在该区域，随之出现的返混现象也在一定程度上加强了混合效果。

关键词: 仿柳叶形, 气流返混, 流动混合特性, 混合, 静态混合器

CLC Number:

TK223.1

FU Xinliang, YAN Zhiyong. Flow and mixing characteristics in willow leaf-like static mixer[J]. CIESC Journal, 2017, 68(12): 4600-4606.

傅鑫亮, 闫志勇. 仿柳叶形静态混合器的流动及混合特性[J]. 化工学报, 2017, 68(12): 4600-4606.

References 34

[1]	王修纲, 郭瓦力, 吴剑华. 静态混合器中液液分散的试验及CFD模拟[J]. 化工学报, 2012, 63(3):767-774. WANG X G, GUO W L, WU J H. Experimental and numerical study on liquid-liquid dispersion in static mixer[J]. CIESC Journal, 2012, 63(3):767-774.
[2]	龚斌, 包忠平, 张春梅, 等. 混合元件数对SK型静态混合器流场特性的影响[J]. 化工学报, 2009, 60(8):1974-1980. GONG B, BAO Z P, ZHANG C M, et al. Effect of number of mixing elements on flow field in Kenics static mixer[J]. CIESC Journal, 2009, 60(8):1974-1980.
[3]	孟辉波, 吴剑华, 禹言芳, 等. 旋流叶片轴向排列对静态混合器混合特性的影响[J]. 哈尔滨工程大学学报, 2009, 30(8):924-929. MENG H B, WU J H, YU Y F, et al. Analysis of the mixing characteristic in static mixers with different axial-arrangements of twisted-leaves[J]. Journal of Harbin Engineering University, 2009, 30(8):924-929.
[4]	齐辉. 静态混合器的作用原理及应用实例[J]. 电大理工, 2006, (1):27-28. QI H. Principle and application of static mixer[J]. Dianda Ligong, 2006, (1):27-28.
[5]	陈俊英, 马晓建. 静态混合器在生物多糖脱色中的应用[J]. 郑州大学学报(工学版), 2003, 24(4):46-49. CHEN J Y, MA X J. Application of static mixer in decolorization of polysaccharides[J]. Journal of Zhengzhou University (Engineering Science), 2003, 24(4):46-49.
[6]	吴雨, 张力钧, 宋忠俊. 静态混合器在石油化工中的应用[J]. 天然气与石油, 2014, 32(3):23-26+8-9. WU Y, ZHANG L J, SONG Z J. Application of static mixer in petrochemical industry[J]. Natural Gas and Oil, 2014, 32(3):23-26+8-9.
[7]	THAKUR R K, VIAL C, NIGAM K D P, et al. Static mixers in the process industries-a review[J]. Chemical Engineering Research & Design, 2003, 81(7):787-826.
[8]	GHANEM A, Lemenand T, Valle D D, et al. Static mixers:mechanisms, applications, and characterization methods-a review[J]. Chemical Engineering Research & Design, 2014, 92(2):205-228.
[9]	吴卫红, 徐甸, 苏传城, 等. X型静态混合器流场数值模拟研究[J]. 能源工程, 2015, (5):45-49. Wu W H, Xu D, Su C C, et al. Study on numerical simulation of flow fied for X-shaped static mixer device[J]. Energy Engineering, 2015, (5):45-49.
[10]	张国锋, 张琴, 张慢来, 等. 基于流场模拟的新型静态混合器结构优化[J]. 石油机械, 2015, 43(11):92-95. Zhang G F, Zhang Q, Zhang M L, et al. Optimization of a new static mixer based on CFD simulation[J]. China Petroleum Machinery, 2015, 43(11):92-95.
[11]	Hirschberg S, Koubek R, Moser F, et al. An improvement of the Sulzer SMX™ static mixer significantly reducing the pressure drop[J]. Chemical Engineering Research & Design, 2009, 87(4):524-532.
[12]	裴煜坤. SCR烟气脱硝系统喷氨混合装置优化研究[D]. 杭州:浙江大学, 2013. Pei Y K. Optimization study on ammonia injection and mixing device of SCR system[D]. Hangzhou:Zhejiang University, 2013.
[13]	KEVIN R, MEL A, MICHAEL V. Numerical modeling for design optimization of SCR applications[C]//ICAC NOx Forum. Washington:ICAC, 2000.
[14]	Cho J M, Choi J W, Hong S H, et al. The methodology to improve the performance of a selective catalytic reduction system installed in HRSG using computational fluid dynamic analysis[J]. Environment Engineering Science, 2006, 23(5):863-873.
[15]	蔡巧梅. 仿树叶型静态混合元件流动与混合特性研究[D]. 杭州:中国计量学院, 2015. Cai Q M. Research on flow and mixing characteristic of leaf of static mixer elements[D]. Hangzhou:China Jiliang University, 2015.
[16]	王伟. SCR脱硝反应器入口烟道流场模拟研究[D]. 济南:山东大学, 2010. Wang W. Numerical simulation research on the flow field of the entrance flue of SCR DeNOx reactor[D]. Jinan:Shandong University, 2010.
[17]	毛剑宏. 大型电站锅炉SCR烟气脱硝系统关键技术研究[D]. 杭州:浙江大学, 2011. Mao J H. Key technology study of SCR flue gas DeNOx system in large power plant boiler[D]. Hangzhou:Zhejiang University, 2011.
[18]	Schreifels J J, Wang S X, Hao J M. Design and operational considerations for selective catalytic reduction technologies at cial-fired boilers[J]. Frontiers in Energy, 2012, 6(1):98-105.
[19]	李之光. 相似与模化的理论及应用[M]. 北京:国防工业出版社, 1982. Li Z G. Similarity and Modeling Theory and Application[M]. Beijing:National Defense Industry Press, 1982.
[20]	赵成东, 孙文举, 殷晓红, 等. 锅炉炉膛空气动力场的冷态等温模化[J]. 黑龙江电力, 2000, 22(5):17-18. Zhao C D, Sun W J, Yin X H, et al. Cold isothermal simulation of air dynamic field in boiler chamber[J]. Heilongjiang Electric Power, 2000, 22(5):17-18.
[21]	王丽君, 佟丽莉. 地面雷达天线罩风载下的数值模拟与风洞试验研究[J]. 工程力学, 2016, 33(S1):283-289. Wang L J, Tong L L. Numerical simulation and wind tunnel test on ground radome under wind lode[J]. Engineering Mechanics, 2016, 33(S1):283-289.
[22]	蔡小峰. 基于数值模拟的SCR法烟气脱硝技术优化设计[D]. 北京:华北电力大学, 2006. Cai X F. The optimization desigin of SCR DeNOx technology for flue gas based on numerical simulation[D]. Beijing:North China Electric Power University, 2006.
[23]	Rahmani R K, Keith T G, Ayasoufi A. Three-dimensional numerical simulation and performance study of an industrial helical static mixer[J]. Journal of Fluids Engineering, 2003, 127(3):1199-1204.
[24]	Kaci H M, Lemenand T, Valle D D, et al. Effects of embedded streamwise vorticity on turbulent mixing[J]. Chemical Engineering & Processing Process Intensification, 2009, 48(10):1459-1476.
[25]	Jildert E V, Peter F R, Hendrik W H. Three-dimensional numerical simulation of flow and heat transfer in the Sulzer SMX static mixer[J]. Chemical Engineering Science, 1999, 54(12):2491-2500.
[26]	肖世新, 高正明, 黄雄斌. 改进型Ross静态混合器牛顿流体流动的试验与数值模拟[J]. 过程工程学报, 2006, 6(1):6-10. Xiao S X, Gao Z M, Huang X B. Experimental and numerical simulation of Newton fluid flow in an improved Ross static mixer[J]. The Chinese Journal of Process Engineering, 2006, 6(1):6-10.
[27]	牛彩伟, 刘汉涛, 张培华, 等. 基于流场不均匀度对SCR效率影响的探究[J]. 热能动力工程, 2016, 31(10):72-78+127. Niu C W, Liu H T, Zhang P H, et al. Study on the effect of flow field unevenness on SCR efficiency[J]. Journal of Engineering for Thermal Energy and Power, 2016, 31(10):72-78+127.
[28]	Nalbandian H. NOx Control for Coal-fired Plant, CCC/157[R]. London:IEA Clean Coal Centre, 2009.
[29]	Faghihi E M, Shamekhi A H. Development of a neural network model for selective catalytic reduction (SCR) catalytic converter and ammonia dosing optimization using multi objective genetic algorithm[J]. Chemical Engineering Journal, 2010, 165(2):508-516.
[30]	中华人民共和国国家质量监督检验检疫总局, 中国国家标准化管理委员会. 燃煤烟气脱硝技术装备GB/T 21509-2008[S]. 北京:中国标准出版社, 2008. General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China, Standardization Administration of the People's Republic of China. Coal-fired flue gas denitrification technology and equipment. GB/T21509-2008[S]. Beijing:Standards Press of China, 2008.
[31]	Yang W, Meng H, Sheng J. Dynamics of hairpin vortices generated by a mixing tab in a channel flow[J]. Experiments in Fluids, 2001, 30(6):705-722.
[32]	Dong S, Meng H. Flow past a trapezoidal tab[J]. Journal of Fluid Mechanics, 2004, 510:219-242.
[33]	贾志谦. 混合过程及其强化研究进展[J]. 化学工程与装备, 2011, (10):146-149. Jia Z Q. Research progress of mixing process and its strengthening[J]. Chemical Engineering and Equipment, 2011, (10):146-149.
[34]	张兆顺. 湍流理论与模拟[M]. 北京:清华大学出版社, 2006:78. Zhang Z S. Theory and Modeling of Turbulence[M]. Beijing:Tsinghua University Press, 2006:78.