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研究生:謝景揚
研究生(外文):Jing-yang Sie
論文名稱:主動式漸闊型微混合器之效能分析
論文名稱(外文):Analyzing the performance of an active diverging-type micromixer
指導教授:孫珍理
指導教授(外文):Chen-li Sun
學位類別:碩士
校院名稱:國立臺灣科技大學
系所名稱:機械工程系
學門:工程學門
學類:機械工程學類
論文種類:學術論文
論文出版年:2008
畢業學年度:96
語文別:中文
論文頁數:167
中文關鍵詞:主動式微混合器流體穩定性混合指標
外文關鍵詞:active micromixerflow stabilitymixing index
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本研究利用數值模擬與實驗量測的方式,針對主動式微混合器,在隨時間正弦變化之壓力作動下,探討半角與相位差對於混合效率的影響。
在數值模擬方面,將微混合器的半角固定為25°,兩入口處的邊界條件設定為正弦壓力制動,壓力振幅、疊加壓力及頻率分別固定為500 Pa、250 Pa 與100 Hz。由模擬結果可發現,當兩流體入口處的動態壓力恰為反相(antiphase)時,可得最佳混合指標(MI,mixing index) 為0.66,而當制動壓力的相位差為同相(inphase)時,混合效率最差。比較漸闊型微混合器內濃度與流場的衍化可發現,漸闊區內的迴流尾部會對流體造成拉伸效應,改善局部混合。此外,在相位差不為0 時,受到壓力隨時間變化的影響,流體會由一入口直接逆流進另一入口,在下個時間點再被推進至漸闊區的另一邊,使二流體間的接觸面積增加,促進混合。在相位差為π時,匯流區內的迴流會增加流體的三維捲動,使混合效果更佳。
在實驗量測方面,針對不同半角之漸闊型、漸縮型及直管微混合器在改變相位差的條件下,進行濃度場可視化並量化其混合程度。由混合量化結果得知,對於漸闊型微混合器,半角為20°相位差為0.75π時,可得最佳混合效果,CV值為0.04。對於漸縮型微混合器,半角為-30°相位差為0.75π時,可得最佳混合效果CV值為0.09。此外,由可視化結果發現,在漸闊型與直管微混合器內,流體接觸介面皆出現不穩定現象,而在漸縮型微混合器中,流場則呈穩定狀態。故在動態壓力制動下,改變微混合器的半角可藉由流體不穩定現象加強流場的拉伸與折疊,提高混合效率。
In this study, mixing performance of an active micromixer is investigated by numerical simulation and experiments. An active micromixer is comsisted of three sections: the T junction, the mixing section, and the outlet. Two parameters are explored: half angle of the mixing section and phase difference of the two sinusoidal pressure actuations.
A diverging-type micromixer with a half angle of 25° is used in the numerical simulation. At the two inlets, time-varying sinusoidal pressures (amplitude 500 Pa, frequency 100 Hz) superimposed by a constant shift of 250 Pa are applied. From the numerical results, best mixing is achieved with a MI (mixing index) of 0.66 when the actuating pressures are anti-phase (phase difference π). On the contrary, in-phase actuation (phase difference 0) leads to poorest mixing. The evolutions of concentration profiles and flow fields reveal that fluid is stretched by a pair of circulations in the diverging region to enhance local mixing. Furthermore, fluid tends to flow from one inlet directly into the other when the actuating pressures are not inphase. The residual fluid in the opposite inlet is then pushed to the other side of the diverging region. This phenomenon helps to increase the contact area between the two fluids and mixing is improved significantly. At a phase difference of π, the unique circulation in the confluence region leads to three-dimensional helical flow so that best mixing is achieved.
During the experiments, both flow visualization and mixing quantification are conducted. For the diverging-type micromixers, minimum CV (0.04) is accomplished at θ = 20° with a phase difference of 0.75π. For the converging-type micromixers, minimum CV (0.09) is accomplished at θ = -30° with a phase difference of 0.75π. Under dynamic pressure actuations, flow instability is observed for both straight and diverging-type micromixers. Since flow instability tends to enhance the fluid stretching and folding effects,mixing performance can be easily improved by alternating the geometry of the mixing section.
Abstract.................................................................................................................................. i
摘要.....................................................................................................................................iii
符號索引.............................................................................................................................. vi
表目錄...............................................................................................................................viii
圖目錄................................................................................................................................. ix
第一章 導論....................................................................................................................... 1
1.1 前言........................................................................................................................ 1
1.2 文獻回顧................................................................................................................ 1
1.3 研究動機................................................................................................................ 3
第二章 主動式漸闊型微混合器之數值分析..................................................................... 4
2.1 模擬假設與統御方程式......................................................................................... 4
2.2 幾何外形、邊界條件及初始條件設定................................................................ 5
2.2.1 邊界條件與初始條件設定......................................................................... 5
2.2.2 微流體之特性............................................................................................. 6
2.2.3 主動式漸闊型微混合器之對稱性.............................................................. 7
2.3 模型離散化 (Discretization) ................................................................................. 8
2.3.1 網格獨立性測試......................................................................................... 8
2.3.2 時步選取..................................................................................................... 9
2.4 數值分析結果...................................................................................................... 10
2.4.1 相位差對於體積流率之影響................................................................... 10
2.4.2 相位差對混合之影響............................................................................... 11
2.4.3 濃度及流線分布隨時間之衍化............................................................... 13
2.4.4 三維濃度場隨時間之衍化....................................................................... 22
2.4.5 漸闊型微混合器與直管微混合器之比較............................................... 23
第三章 主動式微混合器設計及實驗量測....................................................................... 25
3.1 主動式微混合器光罩設計.................................................................................. 25
3.2 主動式微混合器製程.......................................................................................... 26
3.2.1 矽晶圓清洗............................................................................................... 26
3.2.2 微影製程................................................................................................... 27
3.2.3 PDMS 元件製程........................................................................................ 28
3.2.4 SEM 圖....................................................................................................... 29
3.3 實驗架構.............................................................................................................. 29
3.3.1 雷射掃瞄共軛焦顯微鏡系統................................................................... 30
3.3.2 倒立式顯微鏡........................................................................................... 31
3.3.3 正弦壓力產生機構................................................................................... 31
3.3.4 光電感測器............................................................................................... 32
3.4 實驗量測.............................................................................................................. 33
3.4.1 實驗假設................................................................................................... 33
3.4.2 壓力平衡校正........................................................................................... 34
3.4.3 體積流率量測........................................................................................... 34
3.4.4 濃度場可視化........................................................................................... 35
3.4.5 濃度場量化量測....................................................................................... 35
3.5 不確定性分析...................................................................................................... 36
3.5.1 體積流率之相對不確定性....................................................................... 37
3.5.2 莫耳濃度之相對不確定性....................................................................... 37
3.5.3 Reynolds number 之相對不確定性.......................................................... 38
3.5.4 Péclet number 之相對不確定性................................................................ 39
3.5.5 正弦壓力振盪頻率之相對不確定性....................................................... 39
3.5.6 CV (Coefficient of variance)之不確定性................................................... 39
第四章 實驗結果與分析................................................................................................... 42
4.1 半角對體積流率之影響....................................................................................... 42
4.1.1 穩態量測................................................................................................... 42
4.1.2 動態量測................................................................................................... 43
4.1.3 混合機制比較........................................................................................... 43
4.2 濃度場可視化結果............................................................................................... 44
4.2.1 漸闊型微混合器....................................................................................... 44
4.2.2 漸縮型微混合器....................................................................................... 46
4.2.3 直管微混合器........................................................................................... 46
4.2.4 流體不穩定性現象................................................................................... 46
4.3 濃度場量化分析................................................................................................... 47
第五章 結論與建議........................................................................................................... 49
5.1 結論...................................................................................................................... 49
5.2 建議...................................................................................................................... 50
參考文獻............................................................................................................................. 52
附錄A: ............................................................................................................................... 54
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