转盘离心粒化中丝状成粒特性
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摘要
针对转盘离心粒化工艺,以水为工质开展可视化实验。采用高速摄影仪对液膜波动、液丝断裂等粒化过程进行了捕捉,并利用MATLAB自编程序对获得的图像进行了处理。分析了离心粒化过程中液丝形成过程以及液丝断裂形成液滴的过程。研究了运行工况对液丝、液滴形成机制的影响。讨论了液丝形成对液滴形成的影响并获得了Weber数、Reynolds数对粒化效果的影响程度。结果表明,表面不稳定波是形成液丝的主要因素,且液丝在Rayleigh不稳定性的作用下断裂形成液滴。升高转速或者减小流量有利于获得均匀的小液滴。Weber数对液丝、液滴形成具有显著影响;Reynolds数仅对液丝数目有显著影响。
Aiming at the granulation of molten blast furnace slag by spinning disc, the visualization granulation experiment was conducted using water as the substance. The granulation process including film waving and ligament break-up was captured by high-speed camera. A self-compiled MATLAB program was employed to extract the data from the images. The ligament formation and the process of ligament break-up into droplets during centrifugal granulation were analyzed. Variation of ligament formation and droplet formation with operating conditions was investigated. The qualitative relationship between ligament formation and droplet formation was obtained. The impacts of Weber and Reynolds numbers on ligament number, ligament break-up length, droplets diameter distribution and average diameter were discussed. The results revealed that the ligaments were originated from surface instable waves of liquid film on the spinning disc and the droplets were formed by ligament break-up due to symmetric shocking waves spreading from the ends to the middle of ligament. The number of ligament increased with increasing rotary speed and the distribution of droplets became more highly concentrated as well, while the break-up length of ligaments and the average diameter of droplets were decreased as rotary speed increased. With increasing liquid flow rate, the number of ligaments increased, while the distribution of droplets became less concentrated. The break-up length of ligaments and average diameter were increased with higher liquid flow rate. Besides, larger ligament number or shorter ligament break-up length resulted in smaller droplets. Meanwhile, both of the Weber and Reynolds numbers had significant influence on the ligament formation, while only the Weber number had significant effect on droplet formation. By fitting the experimental data, correlations have been obtained to predict the granulation variation with different operational conditions quantitatively.
Aiming at the granulation of molten blast furnace slag by spinning disc, the visualization granulation experiment was conducted using water as the substance. The granulation process including film waving and ligament break-up was captured by high-speed camera. A self-compiled MATLAB program was employed to extract the data from the images. The ligament formation and the process of ligament break-up into droplets during centrifugal granulation were analyzed. Variation of ligament formation and droplet formation with operating conditions was investigated. The qualitative relationship between ligament formation and droplet formation was obtained. The impacts of Weber and Reynolds numbers on ligament number, ligament break-up length, droplets diameter distribution and average diameter were discussed. The results revealed that the ligaments were originated from surface instable waves of liquid film on the spinning disc and the droplets were formed by ligament break-up due to symmetric shocking waves spreading from the ends to the middle of ligament. The number of ligament increased with increasing rotary speed and the distribution of droplets became more highly concentrated as well, while the break-up length of ligaments and the average diameter of droplets were decreased as rotary speed increased. With increasing liquid flow rate, the number of ligaments increased, while the distribution of droplets became less concentrated. The break-up length of ligaments and average diameter were increased with higher liquid flow rate. Besides, larger ligament number or shorter ligament break-up length resulted in smaller droplets. Meanwhile, both of the Weber and Reynolds numbers had significant influence on the ligament formation, while only the Weber number had significant effect on droplet formation. By fitting the experimental data, correlations have been obtained to predict the granulation variation with different operational conditions quantitatively.
引文
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[16]Yan Zhaomin(闫兆民),Zhou Yangmin(周扬民),et al.Experimental study of plates dry granulation of BF slag[J].Energy for Metallurgical Industry(冶金能源),2010,29(3):44-46.
[17]Du Bin(杜滨),Zhang Yanguo(张衍国).Centrifugal granulation experimental study of molten blast furnace slag by rotary disc[J].Energy for Metallurgical Industry(冶金能源),2013,32(4):29-32.
[18]Chen Xiaoyan(陈小艳),Zhou Wu(周骛),Cai Xiaoshu(蔡小舒),et al.Particle size distribution measurement of large spray by imaging[J].CIESC Journal(化工学报),2014,65(2):480-487.
[19]Dombrowski N,Johns W R.The aerodynamic instability and disintegration of viscous liquid sheets[J].Chemical Engineering Science,1963,18(3):203-214.
[20]Leneweit G,Roesner K G,Koehler R.Surface instabilities of thin liquid film flow on a rotating disk[J].Experiments in Fluids,1999,26(1/2):75-85.
[21]Strutt J W,Rayleigh L.On the instability of jets[J].Proc.London Math.Soc.,1878,10:4-13.
[22]Kamiya T.Analysis of the ligament-type disintegration of thin liquid film at the edge of a rotating disc[J].Journal of Chemical Engineering of Japan,1972,5(4):391-396.
[23]Castleman R A.The mechanism of the atomization of liquids[J].Bureau of Standards Journal of Research,1930,6:369-376.
[24]Schweitzer P H.Mechanism of disintegration of liquid jets[J].Journal of Applied Physics,1937,8(8):513-521.
[25]Bergwerk W.Flow pattern in diesel nozzle spray holes[J].Proceedings of the Institution of Mechanical Engineers,1959,173(1):655-660.
[26]Shkadov V Y.Wave flow regimes of a thin layer of viscous fluid subject to gravity[J].Fluid Dynamics,1967,2(1):29-34.
[27]Li Kai(李凯),Wang Hong(王宏),Zhu Xun(朱恂),Liao Qiang(廖强),Wu Junjun(吴君军).Experiment of liquid centrifugal atomization properties by rotary cup[J].Iron and Steel(钢铁),2014,10:95-99.
[28]Yang Hu(杨虎),Liu Qiongsun(刘琼荪),Zhong Bo(钟波).Mathematical Statistics(数理统计)[M].Beijing:Higher Education Press,2004.
[2]Yoshida H N Y,Nakatani G,Anazi T,Sato H.The technology of slag heat recovery at NKK//SEAISI Conference of Energy Utilization in the Iron and Steel Industry[C].1984.
[3]Rodd L K T,Walker C,Voermann N.Economics of slag heat recovery from ferronickel slags//Sustainability for Profit.Conference of Metallurgists(COM2010)[C].2010:3-17.
[4]Xie D,Norgate T,Jahanshahi S.Dry granulation of slags–turning waste into valuable cement binder[J].CAMP-ISIJ,2005,18:1088-1091
[5]Mizuochi T,Akiyama T.Cold experiments of rotary vaned-disks and wheels for slag atomization[J].ISIJ International,2003,43(9):1469-1471.
[6]Ahmed M,Youssef M S.Influence of spinning cup and disk atomizer configurations on droplet size and velocity characteristics[J].Chemical Engineering Science,2014,107:149-157.
[7]Liu J,Yu Q,Guo Q.Experimental investigation of liquid disintegration by rotary cups[J].Chemical Engineering Science,2012,73:44-50.
[8]Liu J,Yu Q,Li P,et al.Cold experiments on ligament formation for blast furnace slag granulation[J].Applied Thermal Engineering,2012,40:351-357.
[9]Min Y,Huang J,Liu C,et al.Physical simulation of molten slag granulation by rotary disk[J].Journal of Iron and Steel Research:International,2013,20(9):26-32.
[10]Zhu X,Zhang H,Tan Y,et al.Analogue experimental study on centrifugal-air blast granulation for molten slag[J].Applied Thermal Engineering,2014.
[11]Xie J W,Zhao Y Y,Dunkley J J.Effects of processing conditions on powder particle size and morphology in centrifugal atomisation of tin[J].Powder Metallurgy,2004,47(2):168-172.
[12]Pan Y,Witt P,Kuan B,Xie D.CFD modelling of the effects of operating parameters on the spreading of liquids on a spinning disc[J].The Journal of Computational Multiphase Flows,2014,6:49-64.
[13]Pan Y,Witt P J,Xie D.CFD simulation of free surface flow and heat transfer of liquid slag on a spinning disc for a novel dry slag granulation process[J].Progress in Computational Fluid Dynamics,2010,10:292-9.
[14]Pan Y,Witt P,Kuan B,Xie D.CFD simulation of slag droplet formation by a spinning disc in dry slag granulation processes[C]//8th International Conference on Computational Fluid Dynamics in the Oil&Gas,Metallurgical and Process Industries[C].Trondheim,2011.
[15]Yang Zhiyuan(杨志远),Zhou Yangmin(周扬民),et al.Experimental study of dry centrifugal granulation of blast furnace slag[J].Science Technology and Engineering(科学技术与工程),2009,(23):7257-7260.
[16]Yan Zhaomin(闫兆民),Zhou Yangmin(周扬民),et al.Experimental study of plates dry granulation of BF slag[J].Energy for Metallurgical Industry(冶金能源),2010,29(3):44-46.
[17]Du Bin(杜滨),Zhang Yanguo(张衍国).Centrifugal granulation experimental study of molten blast furnace slag by rotary disc[J].Energy for Metallurgical Industry(冶金能源),2013,32(4):29-32.
[18]Chen Xiaoyan(陈小艳),Zhou Wu(周骛),Cai Xiaoshu(蔡小舒),et al.Particle size distribution measurement of large spray by imaging[J].CIESC Journal(化工学报),2014,65(2):480-487.
[19]Dombrowski N,Johns W R.The aerodynamic instability and disintegration of viscous liquid sheets[J].Chemical Engineering Science,1963,18(3):203-214.
[20]Leneweit G,Roesner K G,Koehler R.Surface instabilities of thin liquid film flow on a rotating disk[J].Experiments in Fluids,1999,26(1/2):75-85.
[21]Strutt J W,Rayleigh L.On the instability of jets[J].Proc.London Math.Soc.,1878,10:4-13.
[22]Kamiya T.Analysis of the ligament-type disintegration of thin liquid film at the edge of a rotating disc[J].Journal of Chemical Engineering of Japan,1972,5(4):391-396.
[23]Castleman R A.The mechanism of the atomization of liquids[J].Bureau of Standards Journal of Research,1930,6:369-376.
[24]Schweitzer P H.Mechanism of disintegration of liquid jets[J].Journal of Applied Physics,1937,8(8):513-521.
[25]Bergwerk W.Flow pattern in diesel nozzle spray holes[J].Proceedings of the Institution of Mechanical Engineers,1959,173(1):655-660.
[26]Shkadov V Y.Wave flow regimes of a thin layer of viscous fluid subject to gravity[J].Fluid Dynamics,1967,2(1):29-34.
[27]Li Kai(李凯),Wang Hong(王宏),Zhu Xun(朱恂),Liao Qiang(廖强),Wu Junjun(吴君军).Experiment of liquid centrifugal atomization properties by rotary cup[J].Iron and Steel(钢铁),2014,10:95-99.
[28]Yang Hu(杨虎),Liu Qiongsun(刘琼荪),Zhong Bo(钟波).Mathematical Statistics(数理统计)[M].Beijing:Higher Education Press,2004.