- 學位論文
圓錐形攪拌器對黏性流中氣泡上升之影響
Influence of the conical stirrer on bubble rising in viscous flow
摘要
3D 列印相較於傳統製造方法，能以較少的成本依據患者需求進行設計，故近期在 醫療器材之應用上蓬勃發展。該方法是將粉末形態的塑料置於料桶噴頭處，經加熱融 化後再進行列印。由於粉末顆粒間存在空隙，因而熔化後之液體將包覆部分氣體形成 氣泡。該氣泡將導致列印過程塑料輸出不連續，進而影響列印成品之外型及機械強度。 因該流體高黏度之特性，致使氣泡無法依靠其密度差自由上升，因而尋求有效的除氣 機制成為本論文的重要議題。 為此，本文採用流體體積法(Volume of Fluid)，模擬氣泡在黏性流體中的上升行為。 已知醫療粉末塑料熔融後具有高黏度之特性，但缺乏其他相關之材料特性，故採同為 高黏度且已知材料特性之甘油作為研究對象。透過利用圓錐形的攪拌器使流體產生強 制對流，探討其對上升行為之影響。相關之探討參數包含：不同濃度之流體(黏度範圍 為 0.17 ~1.657 Pa s )、攪拌器參數設定(旋轉速度 0 ~2000rad s 、旋轉半徑 0.001m ~ 0.007m)。藉由監測氣泡的數值結果得知：隨著濃度增加，其流體黏度影響 氣泡上升速度影響愈明顯；轉速增大可以使慣性力提升，增加攪拌器對氣泡上升的效 果；增加旋轉半徑使攪拌器的接觸面積增加，增加強制對流影響的範圍；上述攪拌器 參數的結果變化趨勢不受濃度效應影響。由氣泡最高點隨時間之變化可觀察得知，當 氣泡在黏度最高的100% 甘油內，攪拌器以旋轉半徑0.007m及轉速1000rad s 操作條 件下，氣泡可最快獲得強制對流效應，其上升所需時間相較未採用攪拌器之情況可減 少49.71%。
並列摘要
Compared with traditional manufacturing methods, 3D printing can be designed according to the needs of patients at a lower cost, so it has recently developed vigorously in the application of medical equipment. This method is to place the plastic in powder form at the nozzle of the barrel, and then heat and melt it before printing. Due to the existence of voids between powder particles, the molten liquid will coat part of the gas to form bubbles. The bubbles will lead to discontinuous plastic output during the printing process, thereby affecting the appearance and mechanical strength of the printed product. Due to the high viscosity of the fluid, the bubbles cannot rise freely depending on the density difference. Therefore, the search for an effective degassing mechanism has become an important topic of this thesis. Therefore, this paper adopts the Volume of Fluid method to simulate the rising behavior of bubbles in viscous fluid. It is known that the medical powder plastic has the characteristics of high viscosity after melting, but it lacks other related material characteristics, so glycerol, which is also high viscosity and has known material characteristics, is used as the research object. By using a conical agitator to generate forced convection of the fluid, the effect on the ascent behavior was investigated. The relevant discussion parameters include: fluids with different concentrations (viscosity range is 0.17 ~1.657 Pa s ), stirrer parameter settings (rotation speed 0 ~ 2000rad s , rotation radius 0.001m ~ 0.007m). By monitoring the numerical results of the bubbles, it is known that as the concentration increases, the fluid viscosity affects the bubble rising speed more obviously; the increase of the rotational speed can increase the inertial force and increase the effect of the agitator on the bubble rising; increase the rotation radius to make the agitator increase. The contact area of increased, and the range of forced convection influence was increased; the results of the above agitator parameters were not affected by the concentration effect. It can be observed from the change of the highest point of the bubbles with time that when the bubbles are in the 100% glycerin with the highest viscosity, the agitator can obtain the forced convection effect at the fastest speed under the operating conditions of a rotating radius of 0.007m and a rotation speed of 1000rad s . The time required for its rise can be reduced by 49.71% compared with the case where no stirrer is used.
參考文獻
延伸閱讀
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