本研究目的為設計一個在1公分長度內快速達到90%氣體混合的混合器，因此以數值模擬軟體ANSYS CFX探討氮氣與氧氣在具結構物之T 型微混合器內的混合特性與其溫度效應，流道設計為入口及主流道皆長10 mm、寬 1 mm、高0.125 mm的T型微混合器，並在其主流道上下壁面加入四對交錯三角形結構物，其中三角形高定為0.4 mm。針對壁面三角形的形狀、間距進行特性分析，之後加入中心結構物並改變入口雷諾數，最後分別比較一般T型微混合器與具結構物之T型微混合器於不同進氣溫度條件下的混合特性。
在壁面三角形形狀模擬中，其前傾角為改變速度的主要因素，且越接近90度流體v方向的速度越會提升，因此在控制出口混合效率及入出口壓差方面，前傾角效果相較於後傾角更明顯，且特性在前傾角為90度之後影響逐漸變小。在壁面三角形間距模擬中，結構物間距增加，雖會降低v方向的速度，但可使高流速區域面積增加，因此可有效提高出口混合效率並大幅降低入出口壓差。在中心結構物模擬中，分別加入三種中心結構物，欲利用撞擊中心結構物分離流體的效果提高混合效率，其發現在壁面結構物前先置一中心矩形結構物最有效，且控制此結構物之長可有效控制出口混合效率，但入出口壓差會進一步提升。在不同雷諾數模擬中，將氧氣入口雷諾數改為50、150進行模擬，可發現中心結構物在任此雷諾數區間內都可以有效增進混合效率，而在雷諾數100時，因混合效率已鄰近100 %，因此其反應在混合長度的縮短上。整體來說，壓差則因中心結構物的長的增加而更容易隨著雷諾數提升而上升。在溫度模擬中，分別對無結構物與具結構物微混合器進行模擬。在無結構模擬中，溫度的提升會使氣體的黏度上升、密度下降。為了使氧氣入口雷諾數一致，流道內整體速度上升，但無結構物主要依靠擴散作用主導，因此u方向速度的上升反而使流體有更少時間混合，因此混合效率些微下降，但入出口壓差因此上升。在具結構物模擬中，溫度提升會導致氣體黏度依舊上升，因此流道內整體速度皆上升，但由於u方向速度的上升幅度較大，導致出口混合效率些微降低，但由於整體速度皆大幅上升，入出口壓差大幅上升。

The aim of this research is to design a micromixer that quickly reaches 90% gas mixing efficiency within a mixing length of 1 cm. The numerical simulation software ANSYS CFX was used to investigate the mixing characteristics of nitrogen and oxygen mixing in passive micromixers with different structure and the temperature effects. The mixers are designed as T-type micromixers with the mixing length of 10 mm, the width of 1 mm, and the height of 0.125 mm for both entrance and the mixing channel. Four pairs of staggered triangular structures are added to the upper and lower walls of the mixing channel. The triangle height is set to 0.4 mm. Characteristic analysis of the shape and distance of the wall triangle was performed. The effects of central structure and the Reynolds number of the inlet flow were also discussed. Finally, the mixing characteristics of T-type micromixers and structured T-type micromixers with different inlet temperatures was investigated.
In the simulation of the triangular shape of the wall structures, the front angle is the main factor to affect the flow speed in the mixing channel. The velocity in the v direction of the fluid will increase as the front angle approaching to 90 degrees. Therefore, in terms of enhancing the mixing efficiency and the pressure difference between the inlet and the outlet, the change of the front angle is more effective than the back angle. This effect gradually decreases after the front angle increasing over 90 degrees. In the discussion of the distance effect of the wall triangle structures, the increase of the distance between the structures will reduce the velocity in the v direction. However, it will enlarge the area of the high velocity area. Therefore, the mixing efficiency at the outlet can be effectively improved and the pressure difference between the inlet and outlet can be greatly reduced. With the discussion of central obstruction designs, three kinds of central obstructions are used. It was found that it was most effective to place a central rectangular obstruction in front of the wall structure. Changing the length of this structure can effectively control the mixing efficiency at the outlet, but the pressure difference between the inlet and outlet will be further increased. It can be found that the central obstructions can effectively improve the mixing efficiency in any range of this Reynolds number between 50 and 150. In general, the pressure difference is easier to increase with the increase of the Reynolds number due to the increase in the length of the central obstructions. For the discussion of temperature effect, an increase in temperature will increase the viscosity of the gases and decrease the density of the gases with. In order to make the Reynolds number of the oxygen inlet consistent, the velocity in the flow channel increases. The mixing in the unstructured micromixers are mainly dominated by diffusion, so the increase in velocity in the u direction will decrease the residence time for mixing. Therefore, the mixing efficiency is slightly reduced and the pressure difference between the inlet and the outlet is greatly improved. In structured simulations, an increase in temperature will also cause the gas viscosity to rise and the overall velocity in the flow channel to increase. Because the speed increase in the u direction is larger than v direction, the exit mixing efficiency is slightly reduced. However, because the overall speed has risen sharply, the pressure differential between the inlet and the outlet has also improved significantly.

致謝 i
摘要 ii
Abstract iv
目錄 vii
圖目錄 ix
表目錄 xiii
第1章 緒論 1
1.1 研究動機 1
1.2 文獻回顧 3
1.2.1 微混合器分類 3
1.2.2 無結構物微混合器 5
1.2.3 具結構物或改變流道形狀之微混合器 14
1.3 研究目的 24
第2章 模擬設定 28
2.1 微混合器數值模擬 28
2.2 數值模擬邊界條件設定 28
2.3 統御方程式 29
2.4 重要計算參數 33
2.5 模擬的流程架構 35
2.6 網格獨立模擬 36
2.7 擷取平面測試 40
第3章 壁面三角形結構物形狀的影響討論 47
3.1 參數設定 47
3.2 後傾角(BA)模擬 47
3.3 前傾角(FA)模擬 53
3.4 最佳結構物形狀模擬參數設定與結果 59
3.4.1 結構物後傾角(BA)探討： 59
3.4.2 結構物前傾角(FA)探討： 60
3.4.3 最適當壁面三角結構物的選擇： 60
第4章 壁面三角形結構物間距與中心結構物的影響討論 66
4.1 壁面三角形結構物間距 66
4.1.1 參數設定 66
4.1.2 結構物間距模擬 66
4.2 中心結構物 72
4.2.1 參數設定 72
4.2.2 中心結構物模擬 72
第5章 不同雷諾數與改變進氣溫度之影響討論 80
5.1 不同雷諾數影響討論 80
5.1.1 參數設定 80
5.1.2 雷諾數模擬 80
5.2 無結構物之T型微混合器的進氣溫度討論 91
5.2.1 參數設定 91
5.2.2 不同溫度下無結構物之T型微混合器討論 92
5.3 具結構物之T型微混合器的進氣溫度討論 99
5.3.1 參數設定 99
5.3.2 不同溫度下具結構物之T型微混合器討論 100
第6章 結論及未來工作 108
6.1 結論 108
6.2 未來工作與建議 111
參考文獻 113

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