摘要
本研究建立了一套可以觀察液滴受熱行為與微爆現象的實驗裝置，針對十六烷和水合成的乳化燃料液滴，觀察其在熱環境中受熱產生微爆的現象和分析相關微爆參數的影響。實驗中藉由熱電偶量測受熱乳化液滴的溫度變化和高速攝影機擷取影像觀察，可以成打y述分析十六烷/水乳化燃料液滴的微爆過程與現象。本研究之重點在於探討不同的環境溫度(Tsur=300℃、400℃和500℃)和含水量百分比(cw=5%、10%、15%、20%、25%、30%、35%和40%)這兩個重要參數對微爆現象、微爆溫度和微爆時間等微爆特性的影響，並針對微爆強度作定性上的分類。 十六烷/水乳化液滴的微爆現象，依照高速攝影機影像觀察微爆後液滴碎化和霧化的情況，可分為直接微爆（Direct explosion，即Mode D）、部分微爆（Partial explosion，即Mode P）、以及膨脹模式（Swelling and ejecting，即Mode S）三種微爆的模式。由十六烷/水乳化液滴受熱時的溫度變化可以分析液滴的微爆時間與微爆溫度的關係。結果顯示在環境溫度300℃時，含水量20%以上才會發生直接微爆；在含水量15%以下時，僅發生部分微爆及膨脹模式，且部分微爆之微爆時間會隨水量增加有增長之趨勢，而直接微爆狀況亦也有與此相同的趨勢產生。在環境溫度為400℃時， 同樣在含水量15%以上才會發生直接微爆的現象，而膨脹模式則僅在含水量20%以下才有可能發生。在環境溫度500℃時，不論何種含水量百分比（5%~40%），皆會發生直接微爆，而膨脹模式則在25%以下才會發生，至於部分微爆則在含水量約10%~30%時發生。 實驗結果得到在含水量較高的情況下，環境溫度較低時，所需的微爆時間皆偏高，且隨著含水量增加（一般需15%以上），直接微爆發生的機會才增大，而微爆溫度的範圍會越集中。含水量越低，則所需的微爆時間相對越長。一般而言，不論含水量多寡，微爆時間都隨著環境溫度升高而縮短，且微爆溫度隨環境溫度升高而升高；此外，本研究亦發現在含水量5%~40%的範圍時，含水量越高(15%以上)，環境溫度高，越容易發生直接微爆，微爆強度會越強。
並列摘要
In the paper, we heated an n-hexadecane and water emulsified drop in a high temperature environment to result in micro-explosion. The heating process was recorded by a high-speed video system. In addition, with two thermocouples, we measured the temperature variations of an emulsified drop during the heating period. Three environmental temperatures, namely 300℃, 400℃, and 500℃, as well as eight different kinds of water contents (cW=5~40%) were adopted to investigate the micro-explosion phenomenon, the temperature and time at the onset of micro-explosion. According to the observations of high-speed video system, the micro-explosion for n-hexadecane and water emulsified drops can be classified into three modes: direct explosion, partial explosion, and swelling and ejecting. The experimental results showed that, at the environmental temperature of 300℃, direct explosion would occur when water content was higher than 20%. Under the condition of water content lower than 15%, only partial explosion and swelling and ejecting would take place and the onset of micro-explosion time of partial explosion increased with the increase of water content. The same trend was found for direct explosion. At the environmental temperature of 400℃, direct explosion occurred when water content was over 20%; under the condition of water content below 20%, only swelling and ejecting appeared. Irrespective of water contents, direct explosion always took place at the environmental temperature of 500℃; swelling and ejecting, however, was present merely under the condition of water content cW=25%. From cW=10% to 30%, partial explosion would occur. The experimental results revealed that at high water content and low environmental temperature, micro-explosion would take a longer time. With the increase of water content, the probability for direct explosion increased accordingly, and the range of temperature for micro-explosion would be concentrated. The lower the water content, the longer micro-explosion time would take. In general, micro-explosion time decreased with the increase of environmental temperature whereas micro-explosion temperature increased with the increase of environmental temperature. In this research, we also found that from cW=5% to 40%, the higher the water content, the easier the direct explosion would occur, and micro-explosion’s strength would be stronger.