臺灣博碩士論文加值系統

本研究建立了一套觀察液滴受熱行為與微爆現象的裝置，並提出一種異於一般乳化燃料液滴的複合液滴，其特色是不需界面活性劑混合，液滴受熱時即有類似乳化燃料液滴的微爆效果。試驗液體包括：十六烷與水的複合液滴，非純物質的複合液滴，十六烷與水的乳化燃料液滴。本研究的重點在於微爆現象與其他參數的相關性。
複合液滴受熱時的微爆情況，依微爆有無氣泡產生可分為直接與非直接微爆。直接微爆又可依照高速攝影觀察之微爆後液滴碎化情況，將爆炸強度區分為三個等級。在環境溫度為400℃或500℃左右，實驗結果發現，微爆時間越長微爆的溫度越高，但在環境溫度為300℃左右，趨勢較不明顯。而複合液滴的水量變化對於微爆時間及微爆溫度，看不出有明顯的影響。複合液滴的微爆強度方面，微爆時間越長，微爆溫度越高，微爆強度就越強，其中的機制可能與水過熱吸收能量，然後在蒸發時瞬間大量釋放有關，但複合液滴中水滴的大小或水滴與燃料的比例對於微爆強度沒有明顯的影響。
非純物質複合液滴的實驗結果，其微爆的狀況與純物質複合液滴相似，但液滴受熱過程中常發現在油-水界面間產生一連串的微小氣泡，這些微小氣泡可能是由非均勻成核機制產生。乳化燃料液滴的實驗發現，其微爆現象與複合液滴不同，微爆的型態傾向於膨脹，鮮少劇烈爆炸，原因可能是內部水滴呈分散狀，而不容易同時成核，所以瞬間汽化的水量較少，而熱電偶的存在也可能對實驗結果造成影響。複合液滴的微爆情況整體而言較乳化燃料液滴劇烈，且不需要加入界面活性劑，具改善噴霧燃燒之潛力。

A compound drop, composed of a fuel shell and a water core, was suspended and heated to micro-explosion. Three ambient temperatures, namely, 300 oC, 400 oC, and 500 oC and two fuels, namely diesel and n-hexadecane, were tested. The heating process was recorded by a high-speed video system, and the time at temperature of the micro-explosion were measured. The experimental results on compound drops were also compared with the micro-explosion of a heated emulsified W/O diesel-water drop.
The micro-explosion of a heated compound drop was classified as either a indirect micro-explosion, if there were quite a few bubbles generated at the shell-core interface before the explosion, or a direct micro-explosion, if few or no bubble could be seen before the explosion. At an ambient temperature of 400 oC or 500 oC, the micro-explosion time was observed to increase with the micro-explosion temperature; but this trend was not as obvious at 300 oC ambient temperature. The intensity of the micro-explosion rose as the micro-explosion time lengthened, because the accumulation of thermal energy within the over-saturated water core drop grew to a higher extent. However, the size of the core water drop was not seen to influence either the micro-explosion time or micro-explosion temperature.
Compared with pure n-hexadecane and pure water, the impurities or microscopic air bubbles in diesel and dyed water enhanced nonhomogenous nucleation and thus more steam bubbles were produced before micro-explosion. Furthermore, contrary to the intense micro-explosion of a compound drop, a heated emulsified diesel-water drop generally expanded, and followed by squirting of steam to relieve the pressure within the expanded drop. The distributed microscopic water drops in an emulsified drop acted as nonhomogeneous nucleation sites and made an overall micro-explosion improbable.

總目錄····················································Ⅰ
表目錄····················································Ⅲ
圖目錄····················································Ⅳ
符號說明··················································Ⅶ
一、前言···················································1
1-1 乳化燃料之研究·····································2
1-2 過熱極限···········································6
1-3 研究目的···········································8
二、研究方法···············································9
2-1 實驗方法回顧·······································9
2-2 整體設備··········································10
2-2-1 熱環境與加熱裝置····························10
2-2-2 溫度記錄系統································11
2-2-3 馬達直線移動機構····························12
2-2-4 影像紀錄系統································12
2-2-5 影像與溫度記錄同步系統······················13
2-3 實驗方法··········································13
2-3-1 試驗液滴的基本性質··························13
2-3-2 複合液滴的懸掛過程··························14
2-3-3 實驗流程····································14
2-3-4 複合液滴的直徑量測··························15
2-3-5 同步影像與溫度資料··························15
2-3-6 微爆時間及微爆溫度的量測····················16
2-3-7 液滴周圍之對流熱傳效應的估計················17
三、結果討論··············································19
3-1 純質液滴··········································19
3-1-1 純水液滴····································19
3-1-2 純十六烷液滴································20
3-2 十六烷與水複合液滴································23
3-2-1 以高速攝影機觀察之影像分類··················23
3-2-2 微爆現象與溫度變化··························26
3-2-3 微爆時間、微爆現象與環境溫度················28
3-2-4 微爆溫度、微爆現象與環境溫度················30
3-2-5 直接微爆情況-液滴微爆溫度與微爆時間·········31
3-2-6 直接微爆情況-複合液滴水量與微爆時間·········31
3-2-7 直接微爆情況-複合液滴水量與微爆溫度·········32
3-2-8 微爆強度與其他相關參數······················32
3-3 柴油與染色水複合液滴······························34
3-3-1 非純物質複合液滴之微爆特性··················34
3-3-2 固體表面的影響······························35
3-4 十六烷與純水含界面活性劑的乳化液滴················35
3-4-1 乳化燃料液滴的微爆現象······················36
3-4-1 乳化燃料液滴的溫度變化······················37
四、結論··················································39
五、參考文獻··············································41
六、圖表··················································44

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