PLIF investigation on effects of chamber aspect ratio on flow and mixing in cross-shaped mixers
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摘要: 在10<Re<500时，采用平面激光诱导荧光技术（PLIF）研究了4种腔室宽高比r（r=0.5、1.0、1.5和2.0）的十字型混合器内的流动与混合特征。结果表明：不同腔室宽高比的十字型混合器内均出现了分离流、稳态吞噬流、脉动流和非稳态吞噬流等4种流型。对于稳态吞噬流，r<1.0的腔室内流场由3个共旋涡主导，而r≥1.0的腔室内中心涡和卫星涡旋转方向相反。对于脉动流，在r>1.0的腔室内，中心涡周期性收缩和扩张，且整个腔室内流体脉动，而在r=0.5和1.0的腔室下游出现涡环脱落特征。对于非稳态吞噬流，r=1.0的腔室内发生了旋涡合并和破碎现象，而r=0.5的腔室内中心涡和一侧卫星涡发生周期性合并，未观察到涡破碎；对于r>1.0的腔室，腔室内中心涡经历增长、变形和破碎过程。基于时间平均离析强度（IOS）对腔室内流体混合效果进行了量化，并揭示了混合机制。腔室宽高比的增大，促使吞噬流和脉动流的临界雷诺数显著降低，导致低雷诺数下腔室内流体混合强化。Abstract: Planar Laser-induced Fluorescence （PLIF） was used to study flow and mixing characteristics in cross-shaped mixers with four chamber aspect ratios r（r=0.5, 1.0, 1.5 and 2.0） at 10<Re<500. Results show that, there are four flow regimes in the mixers with different depths, including the segregated flow, steady engulfment flow, pulsation flow and unsteady engulfment flow. For the steady engulfment flow, the flow field is dominated by three co-rotating vortices for r<1.0, but the center and satellite vortices rotate in opposite directions for r≥1.0. For the pulsation flow, the center vortex shrinks and expands periodically, and the fluid oscillates throughout the chamber for r>1.0. For r=1.0 and 0.5, the shedding of vortex rings emerges downstream. For the unsteady engulfment flow, periodical vortex merging and breakup is observed for r=1.0. For r=0.5, vortex breakup is invisible, and instead, the center vortex merges with a satellite vortex periodically. For r>1.0, the center vortex experiences growth, deformation, and breakup processes. Mixing in cross-shaped mixers was evaluated by the time-averaged intensity of segregation （IOS）, and the mixing mechanism is revealed. An increase in chamber aspect ratios decreases the critical Reynolds number for the engulfment flow and pulsation flow, which causes the mixing enhancement in the chamber at low Re.
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Key words:
- cross-shaped mixer /
- engulfment flow /
- pulsation flow /
- mixing /
- PLIF
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图 1 PLIF实验流程图及十字型混合器结构示意图
Figure 1. Schematic diagram of the experimental system and geometry of cross-shaped mixer
图 2 不同腔室宽高比的十字型混合器内y=0平面上的PLIF图片
Figure 2. Flow regimes in the cross-shaped mixer with various chamber aspect ratios
图 3 十字型混合器的Re–r流型相图
Figure 3. The Re–r space map describing different flow regimes in cross-shaped mixers
图 4 不同腔室宽高比的十字型混合器内不同xOy平面上的瞬时PLIF图片
Figure 4. Instantaneous PLIF images of several xOy planes in cross-shaped mixers for various chamber aspect ratios
图 5 十字型混合器内稳态吞噬流型下平面z=0上的中心涡尺度随雷诺数的变化
Figure 5. Size of center vortex on plane z=0 for steady engulfment flows in cross-shaped mixers
图 6 Re=125、r=2.0时十字型混合器内z=0平面上一个周期内不同时刻的PLIF图片
Figure 6. PLIF images on plane z/h=0 at various moments during a period in the cross-shaped mixer for Re=125 and r=2.0
图 7 Re=125、r=2.0时十字型混合器内y=0平面上瞬时PLIF图片和区域（−0.25≤x/h≤0.25和−8.75≤z/h≤8.75）时空图
Figure 7. Instantaneous PLIF image on plane y=0 and spatiotemporal map on region （−0.25≤x/h≤0.25 and −8.75≤z/h≤8.75） in cross-shaped mixer for Re=125 and r=2.0
图 8 不同腔室宽高比的十字型混合器内非稳态吞噬流型下z=0平面上一个周期内不同时刻的PILF图片
Figure 8. PILF images at different moments in a period of the unsteady engulfment flow in cross-shaped mixers for various chamber aspect ratios
图 9 不同雷诺数和腔室宽高比时十字型混合器内脉动流和非稳态吞噬流的无量纲振荡频率
Figure 9. Normalized oscillation frequencies of the pulsation flow and unsteady engulfment flow in cross-shaped mixers for different Re and r
图 10 不同雷诺数和腔室宽高比下十字型混合器内z/h=5平面上的时间平均离析强度
Figure 10. The intensity of segregation of plane z/h=5 in cross-shaped mixer for various Reynolds numbers and chamber aspect ratios
表 1 十字型混合器结构参数
Table 1. Geometrical parameters of the cross-shaped mixer
Mixer No. h/mm wi /mm w/mm I 1000 500 1000 II 1000 1000 1000 III 1000 1500 1000 IV 1000 2000 1000 
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[1] LEE C Y,FU L M. Recent advances and applications of micromixers[J]. Sensors and Actuators B:Chemical,2018,259:677-702. doi: 10.1016/j.snb.2017.12.034 [2] 郭春海,谭俊杰,张玉成. 电磁力作用下微型管道中流体流动与混合的实验研究[J]. 实验流体力学,2012,26(5):1-6,26. doi: 10.3969/j.issn.1672-9897.2012.05.0015):1-6,26 GUO C H,TAN J J,ZHANG Y C. Experimental studies for the fluid flow and mixing under the action of electromagnetic force in the micro-channel[J]. Journal of Experiments in Fluid Mechanics,2012,26(5):1-6,26. doi: 10.3969/j.issn.1672-9897.2012.05.001 [3] 张建伟,马彦东,王显旺,等. 撞击流混合器内速度脉动的间歇性分析[J]. 实验流体力学,2012,26(2):6-11. doi: 10.3969/j.issn.1672-9897.2012.02.002ZHANG J W,MA Y D,WANG X W,et al. Intermittence analysis of velocity pulse signal in impinging stream mixer(ISM)[J]. Journal of Experiments in Fluid Mechanics,2012,26(2):6-11. doi: 10.3969/j.issn.1672-9897.2012.02.002 [4] BRIMMO A T,QASAIMEH M A. Stagnation point flows in analytical chemistry and life sciences[J]. RSC Advances,2017,7(81):51206-51232. doi: 10.1039/c7ra11155j [5] 任郑玲,卢晨阳,王安杰,等. T型微混合器合成Cu2O纳米颗粒[J]. 化工学报,2017,68(6):2611-2617. doi: 10.11949/j.issn.0438-1157.20170024REN Z L,LU C Y,WANG A J,et al. Synthesis of Cu2O nanoparticles in T-shaped micro-mixer[J]. CIESC Journal,2017,68(6):2611-2617. doi: 10.11949/j.issn.0438-1157.20170024 [6] 张建伟,闫宇航,沙新力,等. 撞击流强化混合特性及用于制备超细粉体研究进展[J]. 化工进展,2020,39(3):824-833. doi: 10.16085/j.issn.1000-6613.2019-0925ZHANG J W,YAN Y H,SHA X L,et al. Advances on impinging stream intensification mixing mechanism for preparing ultrafine powders[J]. Chemical Industry and Engineering Progress,2020,39(3):824-833. doi: 10.16085/j.issn.1000-6613.2019-0925 [7] AIT MOUHEB N,MALSCH D,MONTILLET A,et al. Numerical and experimental investigations of mixing in T-shaped and cross-shaped micromixers[J]. Chemical Engineering Science,2012,68(1):278-289. doi: 10.1016/j.ces.2011.09.036 [8] 肖水云,李鸣,杨大勇. T型微混合器内混合强化的数值模拟[J]. 应用数学和力学,2016,37(3):301-310. doi: 10.3879/j.issn.1000-0887.2016.03.008XIAO S Y,LI M,YANG D Y. Numerical simulation of mixing enhancement in T-shaped micromixers[J]. Applied Mathematics and Mechanics,2016,37(3):301-310. doi: 10.3879/j.issn.1000-0887.2016.03.008 [9] MARIOTTI A,GALLETTI C,BRUNAZZI E,et al. Steady flow regimes and mixing performance in arrow-shaped micro-mixers[J]. Physical Review Fluids,2019,4(3):034201. doi: 10.1103/physrevfluids.4.034201 [10] HSIEH S S,LIN J W,CHEN J H. Mixing efficiency of Y-type micromixers with different angles[J]. International Journal of Heat and Fluid Flow,2013,44:130-139. doi: 10.1016/j.ijheatfluidflow.2013.05.011 [11] ENGLER M,KOCKMANN N,KIEFER T,et al. Numerical and experimental investigations on liquid mixing in static micromixers[J]. Chemical Engineering Journal,2004,101(1-3):315-322. doi: 10.1016/j.cej.2003.10.017 [12] BOTHE D,STEMICH C,WARNECKE H J. Fluid mixing in a T-shaped micro-mixer[J]. Chemical Engineering Science,2006,61(9):2950-2958. doi: 10.1016/j.ces.2005.10.060 [13] WONG S H,WARD M C L,WHARTON C W. Micro T-mixer as a rapid mixing micromixer[J]. Sensors and Actuators B:Chemical,2004,100(3):359-379. doi: 10.1016/j.snb.2004.02.008 [14] HOFFMANN M,SCHLÜTER M,RÄBIGER N. Experimental investigation of liquid-liquid mixing in T-shaped micro-mixers using μ-LIF and μ-PIV[J]. Chemical Engineering Science,2006,61(9):2968-2976. doi: 10.1016/j.ces.2005.11.029 [15] SOLEYMANI A,KOLEHMAINEN E,TURUNEN I. Numerical and experimental investigations of liquid mixing in T-type micromixers[J]. Chemical Engineering Journal,2008,135:S219-S228. doi: 10.1016/j.cej.2007.07.048 [16] FANI A,CAMARRI S,SALVETTI M V. Unsteady asymmetric engulfment regime in a T-mixer[J]. Physics of Fluids,2014,26(7):074101. doi: 10.1063/1.4885451 [17] FANI A,CAMARRI S,SALVETTI M V. Investigation of the steady engulfment regime in a three-dimensional T-mixer[J]. Physics of Fluids,2013,25(6):064102. doi: 10.1063/1.4809591 [18] REDDY CHERLO S K,PUSHPAVANAM S. Effect of depth on onset of engulfment in rectangular micro-channels[J]. Chemical Engineering Science,2010,65(24):6486-6490. doi: 10.1016/j.ces.2010.08.025 [19] THOMAS S,AMEEL T,GUILKEY J. Mixing kinematics of moderate Reynolds number flows in a T-channel[J]. Physics of Fluids,2010,22(1):013601. doi: 10.1063/1.3283063 [20] ZHANG J W,LIU S F,CHENG C,et al. Investigation of three-dimensional flow regime and mixing characteristic in T-jet reactor[J]. Chemical Engineering Journal,2019,358:1561-1573. doi: 10.1016/j.cej.2018.10.112 [21] MARIOTTI A,GALLETTI C,MAURI R,et al. Steady and unsteady regimes in a T-shaped micro-mixer: Synergic experimental and numerical investigation[J]. Chemical Engineering Journal,2018,341:414-431. doi: 10.1016/j.cej.2018.01.108 [22] HAWARD S J,POOLE R J,ALVES M A,et al. Tricritical spiral vortex instability in cross-slot flow[J]. Physical Review E,2016,93(3):031101. doi: 10.1103/PhysRevE.93.031101 [23] ZHANG J W,LI W F,XU X L,et al. Experimental investigation of three-dimensional flow regimes in a cross-shaped reactor[J]. Physics of Fluids,2019,31(3):034105. doi: 10.1063/1.5080501 [24] BURSHTEIN N,ZOGRAFOS K,SHEN A Q,et al. Periodic fluctuations of streamwise vortices in inertia-dominated intersecting flows[J]. Physics of Fluids,2021,33(1):014106. doi: 10.1063/5.0031712 [25] CORREA P G,GOMBA J M,MAC INTYRE J R,et al. Influence of aspect ratio on vortex formation in X-junctions: direct numerical simulations and eigenmode decomposition[J]. Physics of Fluids,2020,32(12):124105. doi: 10.1063/5.0026829 [26] ZHANG W,LI W F,LIU H F,et al. Effects of outlets flow rates ratios on flow patterns in cross-shaped channels[J]. Physics of Fluids,2021,33(6):063601. doi: 10.1063/5.0051008 [27] ALBERINI F,SIMMONS M J H,INGRAM A,et al. Use of an areal distribution of mixing intensity to describe blending of non-Newtonian fluids in a kenics KM static mixer using PLIF[J]. AIChE Journal,2014,60(1):332-342. doi: 10.1002/aic.14237 [28] ZHANG J W,LI W F,XU X L,et al. Effect of geometry on engulfment flow regime in T-jet reactors[J]. Chemical Engineering Journal,2020,387:124148. doi: 10.1016/j.cej.2020.124148 [29] ZHANG W,SHI Z H,XU X D,et al. Oscillation induced by vortex ring shedding in a cross-shaped channel[J]. Chemical Engineering Science,2021,242:116756. doi: 10.1016/j.ces.2021.116756 [30] LOBASOV A S,MINAKOV A V. Analyzing mixing quality in a T-shaped micromixer for different fluids properties through numerical simulation[J]. Chemical Engineering and Processing - Process Intensification,2018,124:11-23. doi: 10.1016/j.cep.2017.11.004 -
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