具螺旋流道和雙螺旋擋板之多層微混合器之數值模擬

Numerical Simulations of Multi-Lamination Micromixers with a Helical Channel and Double-Helical Baffles

廖展威(Chin-Wai Lio)

指導教授 ： 陳漢明

國立臺灣大學/工學院/機械工程學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201902603

摘要

微混合器是實驗室晶片和微型全分析系統中不可或缺的組件。流體在微觀尺度下，因為雷諾數較低，在混合過程中主要依賴分子擴散作用進行混合，但僅依賴分子擴散作用難以有效率的混合流體，所以需要設計能增強混合效率的微混合器。
　　在本研究中，我們提出了一種三維多層微混合器。這種微混合器基於層壓和混沌平流機制來增強混合。其結構包括16條子流，螺旋形狀流道和雙螺旋擋板。16個子流產生多層流動的效果，而螺旋通道中的擋板結構引起混沌平流。數值模擬用於分析微混合器在雷諾數0.1到100範圍內的混合性能，並得出流體物理性質如流場、濃度分佈等的數值結果。然後，我們將擋板角度設計為變數，額外將具有三種不同角度的擋板跟不具擋板的螺旋流道分析結果進行比較。儘管流體在低雷諾數下混合，但混沌平流仍能在具擋板螺旋微流道中產生。而由擋板結構引起三維旋轉流動的影響導致兩種流體的界面拉伸，並且使流體在螺旋微流道中具有較長的流動路徑。因此，具有雙旋轉擋板的微混合器顯示出比沒有擋板的微混合器更高的混合效率。在雷諾數0.1至100的範圍內，所有具有雙旋轉擋板的微混合器在出口處的混合指數(Mixing Index, MI)都超過0.9。

關鍵字

被動式微混合器 ； 多層層壓式 ； 混沌平流 ； 數值模擬 ； 三維結構 ； 螺旋流道 ； 雙螺旋擋板

並列摘要

Micromixer is an important component of Lab-on-a-chip(LOC) and micro-analysis systems (μ-TAS). Fluids at the microscopic scale, because the Reynolds number is low, the mixing process mainly relies on molecular diffusion. However, it is difficult to mix the fluids efficiently only by molecular diffusion, so it is necessary to design a micromixer that can enhance the mixing efficiency.
　　In this paper, we proposed a 3D multi-lamination micromixer. This micromixer enhances mixing based on lamination and chaotic advection mechanisms. Its structure includes sixteen substreams, a helical channel and double-helical baffles. Sixteen substreams create the effect of multi-lamination flows, and the baffles structure induces the chaotic advection in the helical channel. Numerical simulations are used to analyze the mixing performance of the micromixers at Reynolds number from 0.1 to 100, which obtain the numerical results of fluid physics such as flow field and concentration distribution. The design of baffles angles in the helical channel can affect the mixing index. Therefore, we reveal the mixing performance of the micromixers in three difference baffles angles. We also compare with the mixing performance of the micromixer without double-helical baffles. Despite mixing at the low Reynolds number, the proposed micromixers can induce the chaotic advection in the helical channel. The effect of 3D helical flow caused by the baffles structure stretches the interfacial of two fluids and leads the fluids to have a longer flow path in a helical microchannel. Therefore, the mixing efficiency of the proposed micromixers is higher than the micromixer without the baffles structure. In the range of Reynolds number from 0.1 to 100, the proposed micromixers can obtain the outlet mixing index beyond 0.9.

並列關鍵字

Passive micromixer ； Multi-lamination ； Chaotic advection ； Numerical simulations ； Three dimension structure ； Helical channel ； Double-helical baffles

參考文獻

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