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浸入式金屬物對海上漏油現地燃燒行為之影響研究
The Effect of Immersed Metal Objects on the Burning Behavior of in-Situ Burning
摘要
石化燃料洩漏至海洋的事故為全世界環境保護及海洋生態所需防範及探討的議題，為了能有效減少漏油對生態的危害，目前發展許多清理漏油方法，其中現地燃燒（in-situ burning）為目前最快速且有效清除浮油的方法之一，但在水面上燃燒，由於其熱損失大、燃燒速率低，因此為提高燃燒速率，需要減少熱損失的措施，以增加熱能的回饋給燃料。因此本研究使用直徑30 cm、高度10 cm的石英油盤進行實驗，探討不同類型金屬物（圓柱、圓網（孔隙為82 %）、圓片（孔隙為0 %）、圓網柱、圓片柱）浸入燃料中對燃燒速率的影響，並透過熱傳遞估算模型分析浸入式金屬物對燃料燃燒行為之影響，期能了解金屬物浸入之傳熱機制並能最大限度地提高燃燒速率。 結果顯示，在燃料中添加浸入式金屬物可以提高質量損失率，其中圓網柱和圓片柱架設方式具有較高的燃燒速率；隨著金屬物的浸入深度增加，質量損失率也相應增加，這是由於金屬物除了通過異質成核引起氣泡生成外，還通過熱傳遞作用將熱能傳遞至內部燃料，進一步提高燃燒效率。在燃燒過程中觀測到，圓柱金屬物的使得火焰的型態發生改變，降低火焰的脈動頻率使空氣的捲入量增加，並提升火焰高度；可視化氣泡分析結果顯示，燃料中的液相分子在金屬柱表面形成汽化中心，產生氣泡，而這些氣泡在漂浮至表面的過程中帶動周圍燃料的熱對流作用。熱傳遞估算結果顯示，燃料上方的總熱傳遞主要以熱輻射為主，熱傳導的影響非常小。實驗數據證實了金屬物的熱傳遞作用，金屬圓柱和圓片柱的總熱傳遞量明顯高於無架設金屬物，且與燃燒速率呈現相同的趨勢。
並列摘要
In-situ burning (ISB) is effective to deal with the spill oil accidents. However, the burning on water results in huge thermal loss and poor burning efficiency, lowering the burning rate. This study consequently aimed to improve the burning rate of ISB by using immersed metal objects. Five types of metal objects and different immersed depths were investigated. The five types included column, round mesh, round disk, column & round mesh and column & round disk, and the free burning cases were conducted for comparison. Clearly, the presence of metal objects changed the flame appearance and enhanced heterogeneous-nucleation. More bubbles were generated with the immersed objects, and the movement of the bubbles enhanced convection. Additionally, the mass loss rates with the immersed column & mesh and column & disk at liquid surface were higher than that without metal objects for 21% and 17.5%, respectively. More detailed analysis shows that the additional metal objects above the fuel surface plays the role of heat absorber, and the larger flame height due to the presence of the column helps increase the area of heat absorption. Further, the metal below the fuel surface performs the heat releaser, providing extra heat to the fuel. Quantitative heat transfer analysis confirms the results.