在薄型固態燃料上火焰傳播之實驗觀測

Abstract

本論文係以實驗的方式來觀測火焰在薄型固態燃料上傳播的現象。此實驗所改變的參數包括了：(1) 傾斜角、(2) 紙張厚度、(3) 紙張寬度。首先探討傾斜角的影響，發現火焰傳播速度會隨著傾斜角的增加而減小。其次討論紙張厚度對於火焰傳播速度的影響，結果發現，火焰傳播速度會隨著紙張厚度的增加而減小。最後則為紙張寬度的影響，發現向下火焰的傳播速度在q ³ 30°時，紙張的寬度幾乎不會影響到火焰傳播速度。另一方面，向上火焰的傳播速度則是隨著紙張寬度的增加而增加。而在2D及3D現象的討論方面，則是發現火焰前端在紙張厚度比較薄以及紙張寬度比較窄的情況之下，會呈現一個比較好的2D現象。另外，隨著傾斜角度的增加，火焰前端的2D現象則會愈來愈明顯。此外也探討了有無玻璃板對於火焰的影響，發現火焰在沒有玻璃板的情況之下，火焰受到兩旁空氣自然對流引入的影響，呈現一個上下振盪的現象。假如有玻璃板的話，火焰則會相對的穩定。對於樣品A，在垂直向上火焰時，在紙張寬度為0.5 cm時，火焰成長到最後會熄滅。而對於樣品B和C，其極限的紙張寬度則是為1.4 cm。對於垂直向下火焰而言，樣品A的極限紙張寬度為1.1 cm，其火焰成長到最後亦會熄滅。而同樣的情況在樣品B和C則是1.6 cm。其原因為此時火焰的強度已經非常弱了，再加上散失到外界環境的熱量相對的愈來愈多，因此火焰就會熄滅。

This thesis observes the flame spread behaviors and measures the rates over the thin solid fuels by varying three parameters, which are the inclined angle (q), paper thickness (2 ) and separation distance (d), respectively. The flame spread rate decreases as the inclined angle and the thickness increases. For the separation distance effect, it shows having almost no influence on downward flame spread rate for q ³ 30°, whereas for upward flame spread, the flame spread rate is faster as the separation distance becomes wider for all of orientation. The flame front is closer to 2D pattern in a thinner sample or a narrower separation distance. Also, it displays the more 2D likely flame appearance by increasing the inclined angle. Without glass plates, the flame shows an oscillation behavior. On the other hand, the flame is relative stable with an installation of sidewalls. The limiting separation distance is 0.5 cm in Sample A (2 =0.02cm) for vertically upward spreading flame, whereas they are 1.4 cm for sample B (2 =0.01cm) and C (2 =0.005cm). For downward flame spread, the limiting one is 1.1 cm for Sample A, and 1.6 cm for both Sample B and C. It is indicates that upward flame spread is more hazardous.