缝隙式排气管对旋风分离器的性能影响
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摘要
为降低传统旋风分离器工作时排气管内气流高速旋转造成的大量能量损失,将Lapple型旋风分离器的排气管改进为缝隙式排气管,利用数值模拟和实验的方法分析了缝隙式排气管对旋风分离器的性能影响.采用RSM模型对气相流场的切向速度、静压、流动轨迹、湍流强度以及压降进行数值模拟,采用多相流模型中的DPM模型对分离器的分离效率和颗粒运动轨迹进行仿真分析.仿真分析结果与实验验证结果吻合度较好,有较高的预报精度.最终结果表明,缝隙式排气管可使传统旋风分离器的压降下降6.8%,分离效率提升5.5%;当排气管上缝隙长度或宽度增加至一定数值,分离器的分离效率达到最大.随着排气管上缝隙长度或宽度的增加,旋风分离器的分离效率逐渐趋于稳定,压降持续降低;排气管上的矩形缝隙可使排气管内产生旋进涡核(PVC)现象,随着缝隙长度的增加,旋进涡核现象有所减弱,缝隙宽度的变化对旋进涡核现象影响较小;缝隙式排气管可有效抑制普通排气管中心处回流区的产生,并使普通排气管底部以及外旋流的湍流强度降低,从而减少排气管底部的短路流,提高分离效率.通过观察不同颗粒粒径的电石渣颗粒的运动轨迹,可知Lapple型旋风分离器与新型旋风分离器内部流场呈现出有利于固体颗粒分离的组合涡结构,排气管结构的改变并未影响分离腔的原始涡流结构.
To reduce the energy loss caused by the high speed of airflow in the vortex finder during the operation of the traditional cyclone separator,the vortex finder of the Lapple cyclone separator is improved into a slot vortex finder.Then,we analyzed the effect of the slot vortex finder on the performance of the cyclone separator by both numerical simulation and experiment.In a multiphase flow model,we used the Reynolds stress model(RSM) to perform a numerical simulation of the tangential velocity,static pressure,flow trajectory,turbulence intensity,and pressure drop in the gas flow field,and a discrete phase model(DPM) to simulate and analyze the separation efficiency and particle trajectory of the separator.The simulation and experimental results show good coincidence and higher prediction precision.Results show that the slot vortex finder can reduce the pressure drop of the traditional cyclone separator by 6.8% and the separation efficiency is increased by 5.5%.When the length or width of the slot on the exhaust pipe increases to a certain value,the separation efficiency of the separator reaches its peak.With an increase in the length or width of the slot on the exhaust pipe,the separation efficiency of the cyclone separator tends to become stable and the pressure drop continues to decrease.A rectangular slot on the exhaust pipe can cause a precessing vortex core(PVC)to occur in the exhaust pipe.With an increase in the length of the slot,the PVC weakens but a change in the slot width has less influence on the PVC.The slot vortex finder can effectively inhibit the generation of a recirculation zone at the center of the general vortex finder and reduce the turbulence intensity at the bottom and outer swirl of the traditional vortex finder,thus reducing the short-circuit flow at the bottom of the vortex finder and improving the separation efficiency.The observed trajectories of carbide slag particles with different particle sizes indicate that the internal flow fields of the Lapple and proposed cyclone separators produce a combined vortex structure that is beneficial to the separation of solid particles,and the change of exhaust pipe structure does not affect the original vortex structure of the separation chamber.
To reduce the energy loss caused by the high speed of airflow in the vortex finder during the operation of the traditional cyclone separator,the vortex finder of the Lapple cyclone separator is improved into a slot vortex finder.Then,we analyzed the effect of the slot vortex finder on the performance of the cyclone separator by both numerical simulation and experiment.In a multiphase flow model,we used the Reynolds stress model(RSM) to perform a numerical simulation of the tangential velocity,static pressure,flow trajectory,turbulence intensity,and pressure drop in the gas flow field,and a discrete phase model(DPM) to simulate and analyze the separation efficiency and particle trajectory of the separator.The simulation and experimental results show good coincidence and higher prediction precision.Results show that the slot vortex finder can reduce the pressure drop of the traditional cyclone separator by 6.8% and the separation efficiency is increased by 5.5%.When the length or width of the slot on the exhaust pipe increases to a certain value,the separation efficiency of the separator reaches its peak.With an increase in the length or width of the slot on the exhaust pipe,the separation efficiency of the cyclone separator tends to become stable and the pressure drop continues to decrease.A rectangular slot on the exhaust pipe can cause a precessing vortex core(PVC)to occur in the exhaust pipe.With an increase in the length of the slot,the PVC weakens but a change in the slot width has less influence on the PVC.The slot vortex finder can effectively inhibit the generation of a recirculation zone at the center of the general vortex finder and reduce the turbulence intensity at the bottom and outer swirl of the traditional vortex finder,thus reducing the short-circuit flow at the bottom of the vortex finder and improving the separation efficiency.The observed trajectories of carbide slag particles with different particle sizes indicate that the internal flow fields of the Lapple and proposed cyclone separators produce a combined vortex structure that is beneficial to the separation of solid particles,and the change of exhaust pipe structure does not affect the original vortex structure of the separation chamber.
引文
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[3]Lim K S,Kim H S,Lee K W.Characteristics of the collection efficiency for a cyclone with different vortex finder shapes[J].Journal of Aerosol Science,2004,35(6):743-754.
[4]Tan F,Karagoz I,Avci A.The effects of vortex finder dimensions on the natural vortex length in a new cyclone separator[J].Chemical Engineering Communications,2016,203(9):1216-1221.
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[8]Chen J H,Liu X.Simulation of a modified cyclone separator with a novel exhaust[J].Sparation and Purification Technology,2010,73(2):100-105.
[9]Khairy E,Chris L.Numerical modeling of the flow field and performance in cyclones of different cone-tip diameters[J].Computers and Fluids,2011,51(1):48-59.
[10]Brar L S,Sharma R P,Dwivedi R.Effect of vortex finder diameter on flow field and collection efficiency of cyclone separators[J].Particulate Science and Technology,2015,33(1):34-40.
[11]Zhu Y,Lee K W.Experimental study on small cyclones operating at high flowrates[J].Journal of Aerosol Science,1999,30(10):1303-1315.
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[13]Farzad P,Seyyed H H,Goodarz A,et al.Impacts of the vortex finder eccentricity on the flow pattern and performance of a gas cyclone[J].Separation and Purification Technology,2017,187(1):1-13.
[14]Pei B B,Yang L,Dong K J,et al.The effect of crossshaped vortex finder on the performance of cyclone separator[J].Powder Technology,2017,313(3):135-144.
[15]冯静安,唐小琦,王卫兵,等.基于网格无关性与时间独立性的数值模拟可靠性的验证方法[J].石河子大学学报:自然科学版,2017,35(1):52-56.Feng Jing’an,Tang Xiaoqi,Wang Weibing,et al.Reliability verification method of numerical simulation based on grid independence and time independence[J].Journal of Shehezi University:Natural Science,2017,35(1):52-56(in Chinese).
[16]李琴,邹康,刘海东,等.基于颗粒受力的旋风分离器冲蚀机理的研究[J].流体机械,2017,45(3):42-47.Li Qin,Zou Kang,Liu Haidong,et al.The erosion mechanism research of cyclone based on force operating of particles[J].Fluid Machinery,2017,45(3):42-47(in Chinese).
[17]Sujeet K S,Prashant S,Pradyumna G.The effect of modeling of velocity fluctuations onprediction of collection efficiency of cyclone separators[J].Applied Mathematical Modelling,2013,37(8):5774-5789(in Chinese).
[18]唐守强.基于CFD的旋风分离器性能参数影响研究[D].淄博:山东理工大学,2015.Tang Shouqiang.CFD Study of the Parameters Affecting the Performance of a Cyclone Separator[D].Zibo:Shandong University of Technology,2015(in Chinese).
[19]戚贵强.多效旋风分离器的性能研究[D].青岛:青岛科技大学,2010.Qi Guiqiang.Study on Performance of Multi-Effect Cyclone Separator[D].Qingdao:Qingdao University of Science and Technology,2010(in Chinese).
[20]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,2005,5(3):251-254.Wang Jianjun,Wang Lianze,Liu Chengwen.Research on the flow field in the exit tube and the mechanism of pressure drop reduction in a cyclone separator[J].The Chinese Journal of Process Engineering,2005,5(3):251-254(in Chinese).
[21]蒋梦婷.旋风分离器内气固两相流的实验与数值研[D].兰州:兰州大学,2013.Jiang Mengting.Experimental and Numerical Study of the Gas-Solid Flow in a Cyclone Separator[D].Lanzhou:Lanzhou University,2013(in Chinese).
[2]Hoffmann A C,Stein L E.Gas Cyclones and Swirl Channels:Principles,Design and Operation[M].Beijing:Chemical Industry Press,2004.
[3]Lim K S,Kim H S,Lee K W.Characteristics of the collection efficiency for a cyclone with different vortex finder shapes[J].Journal of Aerosol Science,2004,35(6):743-754.
[4]Tan F,Karagoz I,Avci A.The effects of vortex finder dimensions on the natural vortex length in a new cyclone separator[J].Chemical Engineering Communications,2016,203(9):1216-1221.
[5]Raoufi A S,Mehrzad,Farzaneh M E,et al.Numerical simulation and optimization of fluid flow in cyclone vortex finder[J].Chemical Engineering and Processing,2008,47(6):128-137.
[6]Li Q,Xu W W,Wang J,et al.Performance evaluation of a new cyclone separator(Part I):Experimental results[J].Separation and Purification Technology,2015,141(1):53-58.
[7]Hesham M E.Improving cyclone performance by proper selection of the exit pipe[J].Applied Mathematical Modelling,2013,37(7):5286-5303.
[8]Chen J H,Liu X.Simulation of a modified cyclone separator with a novel exhaust[J].Sparation and Purification Technology,2010,73(2):100-105.
[9]Khairy E,Chris L.Numerical modeling of the flow field and performance in cyclones of different cone-tip diameters[J].Computers and Fluids,2011,51(1):48-59.
[10]Brar L S,Sharma R P,Dwivedi R.Effect of vortex finder diameter on flow field and collection efficiency of cyclone separators[J].Particulate Science and Technology,2015,33(1):34-40.
[11]Zhu Y,Lee K W.Experimental study on small cyclones operating at high flowrates[J].Journal of Aerosol Science,1999,30(10):1303-1315.
[12]Gao X,Chen J F,Feng J M,et al.Numerical investigation of the effects of the central channel on the flow field in an oil-gas cyclone separator[J].Computers and Fluids.,2014,92(1):45-55.
[13]Farzad P,Seyyed H H,Goodarz A,et al.Impacts of the vortex finder eccentricity on the flow pattern and performance of a gas cyclone[J].Separation and Purification Technology,2017,187(1):1-13.
[14]Pei B B,Yang L,Dong K J,et al.The effect of crossshaped vortex finder on the performance of cyclone separator[J].Powder Technology,2017,313(3):135-144.
[15]冯静安,唐小琦,王卫兵,等.基于网格无关性与时间独立性的数值模拟可靠性的验证方法[J].石河子大学学报:自然科学版,2017,35(1):52-56.Feng Jing’an,Tang Xiaoqi,Wang Weibing,et al.Reliability verification method of numerical simulation based on grid independence and time independence[J].Journal of Shehezi University:Natural Science,2017,35(1):52-56(in Chinese).
[16]李琴,邹康,刘海东,等.基于颗粒受力的旋风分离器冲蚀机理的研究[J].流体机械,2017,45(3):42-47.Li Qin,Zou Kang,Liu Haidong,et al.The erosion mechanism research of cyclone based on force operating of particles[J].Fluid Machinery,2017,45(3):42-47(in Chinese).
[17]Sujeet K S,Prashant S,Pradyumna G.The effect of modeling of velocity fluctuations onprediction of collection efficiency of cyclone separators[J].Applied Mathematical Modelling,2013,37(8):5774-5789(in Chinese).
[18]唐守强.基于CFD的旋风分离器性能参数影响研究[D].淄博:山东理工大学,2015.Tang Shouqiang.CFD Study of the Parameters Affecting the Performance of a Cyclone Separator[D].Zibo:Shandong University of Technology,2015(in Chinese).
[19]戚贵强.多效旋风分离器的性能研究[D].青岛:青岛科技大学,2010.Qi Guiqiang.Study on Performance of Multi-Effect Cyclone Separator[D].Qingdao:Qingdao University of Science and Technology,2010(in Chinese).
[20]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,2005,5(3):251-254.Wang Jianjun,Wang Lianze,Liu Chengwen.Research on the flow field in the exit tube and the mechanism of pressure drop reduction in a cyclone separator[J].The Chinese Journal of Process Engineering,2005,5(3):251-254(in Chinese).
[21]蒋梦婷.旋风分离器内气固两相流的实验与数值研[D].兰州:兰州大学,2013.Jiang Mengting.Experimental and Numerical Study of the Gas-Solid Flow in a Cyclone Separator[D].Lanzhou:Lanzhou University,2013(in Chinese).