文丘里式气泡发生器渐扩段内单气泡输运过程研究
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摘要
文丘里式气泡发生器渐扩段的流场结构、流动参数等对气泡制备性能起关键作用,因此,对具有矩形截面的文丘里通道渐扩段区域单气泡输运过程进行了可视化研究。分析发现,渐扩段气泡剧烈减速及变形过程对气泡最终的断裂和破碎起关键作用。气泡的减速过程虽只持续数ms时间,依然呈现加速减速和降速减缓两个明显阶段;气泡旋转过程呈现相似的变化规律。在液体流量2.4～6.9 m~3/h范围内,对应最大旋转速度可达900～3 000 rad/s。气泡旋转过程持续时间较减速过程稍长,气泡最大旋转速度的位置出现在最大减速加速度位置的下游约2 mm处;液体流量和气泡尺寸对气泡旋转和变形过程有明显影响,液体流量越大或气泡尺寸越小,气泡旋转过程越剧烈,且旋转速度在更短距离内达到最大值;增大液体流量在一定范围内加剧了气泡的拉伸变形。这些可视化研究结果,为进一步揭示文丘里气泡发生装置内气泡的碎化机制、完善数值分析模型、优化设计等提供参考和帮助。
Flow field and flow parameter, etc., in the diverging section of a Venturi-type bubble generator, are of significance in producing bubbles. A visualized research was consequently carried out on transportation of individual bubbles through a Venturi channel with a rectangular cross-section. The analysis shows that dramatic deceleration and deformation of bubbles in the diverging section play a key role in final split or breakup of bubbles. Within a short period about several milliseconds, a bubble in the diverging section always undergoes an increasing deceleration followed by a decreasing deceleration process, during which the bubble also experiences similar manner in rotation process. The maximum rotation velocity of bubbles is about 900-3 000 rad/s with the liquid flow rate in the range of 2.4 m~3/h to 6.9 m~3/h. However, a bubble would keep rotating and being deformed for a certain period of time after its deceleration process ends. The position of a bubble with the maximum rotation velocity lags behind that of maximum deceleration about 2 mm. Liquid flow rate and bubble size have significant effect on the rotation and deformation process. A larger liquid flow rate or a smaller size always incurs a more violent rotation process for a bubble, and the rotation velocity reaches the maximum in the shorter distance. Increasing liquid flow rate aggravates the deformation of a bubble to a certain degree. The visualized research results provide reference and help to illustrate the bubble breakup mechanism, improve the numerical simulation model and optimize the design.
Flow field and flow parameter, etc., in the diverging section of a Venturi-type bubble generator, are of significance in producing bubbles. A visualized research was consequently carried out on transportation of individual bubbles through a Venturi channel with a rectangular cross-section. The analysis shows that dramatic deceleration and deformation of bubbles in the diverging section play a key role in final split or breakup of bubbles. Within a short period about several milliseconds, a bubble in the diverging section always undergoes an increasing deceleration followed by a decreasing deceleration process, during which the bubble also experiences similar manner in rotation process. The maximum rotation velocity of bubbles is about 900-3 000 rad/s with the liquid flow rate in the range of 2.4 m~3/h to 6.9 m~3/h. However, a bubble would keep rotating and being deformed for a certain period of time after its deceleration process ends. The position of a bubble with the maximum rotation velocity lags behind that of maximum deceleration about 2 mm. Liquid flow rate and bubble size have significant effect on the rotation and deformation process. A larger liquid flow rate or a smaller size always incurs a more violent rotation process for a bubble, and the rotation velocity reaches the maximum in the shorter distance. Increasing liquid flow rate aggravates the deformation of a bubble to a certain degree. The visualized research results provide reference and help to illustrate the bubble breakup mechanism, improve the numerical simulation model and optimize the design.
引文
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[8] 居晓峰,孙立成,唐文偲,等.文丘里式气泡发生器工作特性分析[J].核技术,2014,37(12):120605-1-6.JU Xiaofeng,SUN Licheng,TANG Wencai,et al.Analysis of the operating characteristics of a Venturi-type bubble generator for MSR[J].Nuclear Techniques,2014,37(12):120605-1-6(in Chinese).
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[10] GABBARD C H.Development of a Venturi type bubble generator for use in the molten-salt reactor xenon removal system,ORNL-TM-4122[R].USA:ORNL,1972.
[11] SUN L,MO Z,ZHAO L,et al.Characteristics and mechanism of bubble breakup in a bubble generator developed for a small TMSR[J].Annals of Nuclear Energy,2017,109:69-81.
[12] YIN J,LI J,LI H,et al.Experimental study on the bubble generation characteristics for an Venturi type bubble generator[J].International Journal of Heat and Mass Transfer,2015,91:218-224.
[13] LIAO Y,LUCAS D.A literature review of theoretical models for drop and bubble breakup in turbulent dispersions[J].Chemical Engineering Science,2009,64(15):3 389-3 406.
[14] HINZE J O.Fundamentals of the hydrodynamic mechanism of splitting in dispersion processes[J].AIChE Journal,1955,1(3):289-295.
[15] KOLMOGOROFF A N.On the breaking of drops in turbulent flow[J].Dokl Akad Nauk,1949,66(5):825-828.
[16] FUJIWARA A,OKAMOTO K,HASHIGUCHI K,et al.Bubble breakup phenomena in a Venturi tube[C]//ASME/JSME Joint Fluids Engineering Summer Conference.San Diego:[s.n.],2007:553-560.
[17] UESAWA S,KANEKO A,NOMURA Y,et al.Study on bubble breakup behavior in a Venturi tube[J].Multiphase Science and Technology,2012,24(3):257-277.
[18] SONG Y,WANG D,YIN J,et al.Study of bubble breakup mechanism in a Venturi bubble generator applied in TMSR[C]//17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics.Xi’an:[s.n.],2017:21673.
[19] 邵梓一,张海燕,孙立成,等.文丘里式气泡发生器内气泡破碎机制分析[J].化工学报,2018,69(6):2 439-2 445.SHAO Ziyi,ZHANG Haiyan,SUN Licheng,et al.Bubble breakup mechanism in Venturi-type bubble generator[J].CIESC Journal,2018,69(6):2 439-2 445(in Chinese).
[20] ZHAO L,MO Z,SUN L,et al.A visualized study of the motion of individual bubbles in a Venturi-type bubble generator[J].Progress in Nuclear Energy,2017,97:74-89.
[21] ZHAO L,SUN L,MO Z,et al.An investigation on bubble motion in liquid flowing through a rectangular Venturi channel[J].Experimental Thermal Fluid and Science,2018,97:48-58.
[22] ZHAO L,SUN L,TANG J,et al.Investigation on bubble motion in liquid flowing through a rectangular Venturi channel[C]//17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics.Xi’an:[s.n.],2017:21920.
[23] JO H,JO D.Experimental studies of condensing vapor bubbles in subcooled pool water using visual and acoustic analysis methods[J].Annals of Nuclear Energy,2017,110:171-185.
[24] KUO J,WALLIS G B.Flow of bubbles through nozzles[J].International Journal of Multiphase Flow,1988,14 (5):547-564.
[25] FORRESTER J H,YOUNG D F.Flow through a converging-diverging tube and its implications in occlusive vascular disease,Ⅰ:Theoretical development[J].Journal of Biomechanics,1970,3(3):297-305.
[26] FROM C S,SAURET E,ARMFIELD S W,et al.Turbulent dense gas flow characteristics in swirling conical diffuser[J].Computers and Fluids,2017,149:100-118.
[2] 周艳民,孙中宁,谷海峰,等.自吸式文丘里水洗器引射特性研究[J].原子能科学技术,2015,49(6):1 075-1 079.ZHOU Yanmin,SUN Zhongning,GU Haifeng,et al.Research on injection characteristics of Venturi scrubber worked on self-priming mode[J].Atomic Energy Science and Technology,2015,49(6):1 075-1 079(in Chinese).
[3] 耿坤,董志勇,张凯,等.文丘里空化空蚀杀灭大肠杆菌的试验研究[J].中国环境科学,2017,37(9):3 385-3 391.GENG Kun,DONG Zhiyong,ZHANG Kai,et al.Experimental study of Escherichia coli killed by hydrodynamic cavitation due to Venturi tube[J].China Environmental Science,2017,37(9):3 385-3 391(in Chinese).
[4] SADATOMI M,KAWAHARA A,KANO K,et al.Performance of a new micro-bubble generator with a spherical body in a flowing water tube[J].Experimental Thermal and Fluid Science,2015,29(5):615-623.
[5] TERASAKA K,HIRABAYASHI A,NISHINO T,et al.Development of microbubble aerator for waste water treatment using aerobic activated sludge[J].Chemical Engineering Science,2011,66(14):3 172-3 179.
[6] SADATOMI M,KAWAHARA A,MATSUURA H,et al.Micro-bubble generation rate and bubble dissolution rate into water by a simple multi-fluid mixer with orifice and porous tube[J].Experimental Thermal and Fluid Science,2012,41:23-30.
[7] 唐文偲,阎昌琪,孙立成,等.文丘里式气泡发生器气泡碎化特性研究[J].原子能科学技术,2014,48(5):844-848.TANG Wencai,YAN Changqi,SUN Licheng,et al.Characteristic of bubble breakup in Venturi-type bubble generator[J].Atomic Energy Science and Technology,2014,48(5):844-848(in Chinese).
[8] 居晓峰,孙立成,唐文偲,等.文丘里式气泡发生器工作特性分析[J].核技术,2014,37(12):120605-1-6.JU Xiaofeng,SUN Licheng,TANG Wencai,et al.Analysis of the operating characteristics of a Venturi-type bubble generator for MSR[J].Nuclear Techniques,2014,37(12):120605-1-6(in Chinese).
[9] 莫政宇,杜敏,邵梓一,等.文丘里式气泡发生器内气泡输运过程研究[J].原子能科学技术,2016,50(6):1 034-1 039.MO Zhengyu,DU Min,SHAO Ziyi,et al.Investigation of bubble transportation in Venturi-type bubble generator[J].Atomic Energy Science and Technology,2016,50(6):1 034-1 039(in Chinese).
[10] GABBARD C H.Development of a Venturi type bubble generator for use in the molten-salt reactor xenon removal system,ORNL-TM-4122[R].USA:ORNL,1972.
[11] SUN L,MO Z,ZHAO L,et al.Characteristics and mechanism of bubble breakup in a bubble generator developed for a small TMSR[J].Annals of Nuclear Energy,2017,109:69-81.
[12] YIN J,LI J,LI H,et al.Experimental study on the bubble generation characteristics for an Venturi type bubble generator[J].International Journal of Heat and Mass Transfer,2015,91:218-224.
[13] LIAO Y,LUCAS D.A literature review of theoretical models for drop and bubble breakup in turbulent dispersions[J].Chemical Engineering Science,2009,64(15):3 389-3 406.
[14] HINZE J O.Fundamentals of the hydrodynamic mechanism of splitting in dispersion processes[J].AIChE Journal,1955,1(3):289-295.
[15] KOLMOGOROFF A N.On the breaking of drops in turbulent flow[J].Dokl Akad Nauk,1949,66(5):825-828.
[16] FUJIWARA A,OKAMOTO K,HASHIGUCHI K,et al.Bubble breakup phenomena in a Venturi tube[C]//ASME/JSME Joint Fluids Engineering Summer Conference.San Diego:[s.n.],2007:553-560.
[17] UESAWA S,KANEKO A,NOMURA Y,et al.Study on bubble breakup behavior in a Venturi tube[J].Multiphase Science and Technology,2012,24(3):257-277.
[18] SONG Y,WANG D,YIN J,et al.Study of bubble breakup mechanism in a Venturi bubble generator applied in TMSR[C]//17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics.Xi’an:[s.n.],2017:21673.
[19] 邵梓一,张海燕,孙立成,等.文丘里式气泡发生器内气泡破碎机制分析[J].化工学报,2018,69(6):2 439-2 445.SHAO Ziyi,ZHANG Haiyan,SUN Licheng,et al.Bubble breakup mechanism in Venturi-type bubble generator[J].CIESC Journal,2018,69(6):2 439-2 445(in Chinese).
[20] ZHAO L,MO Z,SUN L,et al.A visualized study of the motion of individual bubbles in a Venturi-type bubble generator[J].Progress in Nuclear Energy,2017,97:74-89.
[21] ZHAO L,SUN L,MO Z,et al.An investigation on bubble motion in liquid flowing through a rectangular Venturi channel[J].Experimental Thermal Fluid and Science,2018,97:48-58.
[22] ZHAO L,SUN L,TANG J,et al.Investigation on bubble motion in liquid flowing through a rectangular Venturi channel[C]//17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics.Xi’an:[s.n.],2017:21920.
[23] JO H,JO D.Experimental studies of condensing vapor bubbles in subcooled pool water using visual and acoustic analysis methods[J].Annals of Nuclear Energy,2017,110:171-185.
[24] KUO J,WALLIS G B.Flow of bubbles through nozzles[J].International Journal of Multiphase Flow,1988,14 (5):547-564.
[25] FORRESTER J H,YOUNG D F.Flow through a converging-diverging tube and its implications in occlusive vascular disease,Ⅰ:Theoretical development[J].Journal of Biomechanics,1970,3(3):297-305.
[26] FROM C S,SAURET E,ARMFIELD S W,et al.Turbulent dense gas flow characteristics in swirling conical diffuser[J].Computers and Fluids,2017,149:100-118.