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研究生:陳祈彰
研究生(外文):CHI-CHANG CHEN
論文名稱:液滴撞擊液膜之飛濺臨界邊界研究
論文名稱(外文):On the critical splashing boundary for single droplet impinge on a liquid film
指導教授:王安邦王安邦引用關係
指導教授(外文):AN-BANG WANG
學位類別:碩士
校院名稱:國立臺灣大學
系所名稱:應用力學研究所
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:1999
畢業學年度:87
語文別:中文
論文頁數:99
中文關鍵詞:液膜飛濺現象
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摘要
本文首先突破過去液滴與液膜交互作用文獻中一直尚未克服之障礙,建立一具能產生精確、穩定而均勻之平面薄液膜設備,同時改善傳統實驗中目測液膜所造成之不確定度。由本文之結果証實這些努力大幅提高此種實驗結果的重覆性及精度,並從而發現液滴撞擊極薄液膜之新特性。本文中所探討產生飛濺現象臨界邊界之主要研究參數為液膜之厚度及工作流體之黏滯性參數之變化皆橫跨兩個數量級以上,此為文獻中對臨界飛濺現象在如此大範圍所做之第一次有系統之探討。
由本文之實驗結果發現:對於單一液滴撞擊液膜所產生飛濺現象之特性,可將其分為出四個不同之特性區域:(Ⅰ)極薄液膜區、(Ⅱ)薄液膜區、(III)厚液膜區以及(IV)極厚液膜區。液膜厚度之效應對薄液膜區及厚液膜區之撞擊行為有明顯之影響;但在其他兩區則否。而在極薄液膜區臨界飛濺參數與液膜厚度無關之特性,及在第(III)區臨界飛濺值,隨膜厚增加反而降低之特性,是文獻中之首次發現。然而不論在任何之特性區域,液體之黏滯性愈大,其臨界飛濺值亦愈高。另外在本文中亦分別就各區域確立其特性邊界,並定量歸納其特性方程式以補足文獻資料的完整性。
The study of droplet-film-interaction has been restricted as a “demonstration” rather than a “investigation” due to its relatively scattered experimental data in the literature since a long time. A novel method has been introduced in this thesis to produce an accurate and repeatable thin film on the test plate. This method avoids the traditional problems from observing and determining the film thickness, which causes the biggest uncertainty of the experiment due to the capillary meniscus in the liquid-wall-interface.
Main efforts of this work is to figure out the critical splashing threshold for single droplet impinging on different viscous fluid with various film thickness. It is found that the splashing phenomena could be classified as four characteristic regimes. They are (I)very thin liquid film, (II)thin liquid film, (III)thick liquid film and (IV)very thick liquid film regimes. The film thickness has significant influences on the splashing threshold for both (II) and (III) regimes, but not for the other two regimes. The new character in the regimes (I) and (III) are the first time introduced in the literature. Among all regimes, the higher viscosity of the fluid, the higher the critical splashing level. The characteristic curve for the splashing threshold has been completely plotted out for the first time in the literature.
摘要………………………………………………………………...I
Abstract…………………………………………………………….II
目錄………………………………………………………………...III
圖表目錄…………………………………………………………...V
符號說明…………………………………………………………...IX
第一章 緒論……………………………………………………………1
1.1 前言……………………………………………………….……..1
1.2 文獻回顧…………………………………………………….…..2
1.3 本文動機…………………………………………….…………..6
第二章 實驗設備與方法…………………………………….………8
2.1 實驗設備..………………….………………………….………...8
2.2 液滴產生器……………………………...………………….…..10
2.3 平面液膜產生器…………………………………….……...…..12
2.4 影像擷取系統…………………………………………………..15
2.5 誤差分析…………...…………………………………...……....16
第三章 產生平面液膜之過程與結果.……………….……..…….19
3.1 淋幕液膜破裂與形成………………………...………….…..…19
3.2 淋幕塗佈缺陷………...………………………………….….….19
3.3 淋幕液膜塗佈視窗之量測…………...……………….…….….21
3.4 平面液膜之塗佈…………………………….………………….22
第四章 液滴正向撞擊液膜之結果與討論………..……….….23
4.1 液膜型態及各區域之特性…………….…………….…………26
4.1.1 薄液膜區之特性……………………………………….….26
4.1.2 極薄液膜區之特性…………………………………….….28
4.1.3 厚液膜區之特性……………...…………………………...29
4.1.4 極厚液膜區之特性……………...………………………...30
4.2 液體黏滯性之效應………………………………………….….31
4.2.1 黏滯性在薄液膜區之影響……...………………………...32
4.2.2 黏滯性在極薄液膜區之影響………….………………….36
4.2.3 黏滯性在厚液膜區與極厚液膜區之影響...……………...37
4.3 歸納與討論………………………………………...…………...38
第五章 結論………………………………….…….………………...43
參考文獻…………………………………………………………...…...46
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Cossali, G. E.,Coghe, A. & Marengo, M., 1997,“The impact of single drop on a wetted solid surface,” Experiments in Fluids, Vol. 22, pp. 463-472.
Cossali, G. E.,, Brunello, G., Coghe, A. & Marengo, M., 1999, “Impact of a single drop on a liquid film: experimental analysis and comparison with empirical models,” Proc. Of the Italian Congress of thermofliuid dynamics UIT, Ferrara, 1999.
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