| Summary: | 碩士 === 國立高雄第一科技大學 === 環境與安全衛生工程研究所 === 99 === Upward flame spread has been recognized to be the fastest flame spread mode due to larger flame height and heating intensity. This study discussed two aspects of upward flame spread. One is the width effect and the other is wind effect.
In the first part, the width effect was investigated on PMMA slabs with width of 100, 30, 500 and 700 mm with and without sidewalls. Flame/pyrolysis height, heat flux, flame temperature, flame thickness and flame spread rate were measured. The experimental results show that the heat feedback was stronger when sidewalls were absent. The volatiles were enhanced toward the central line of samples when sidewalls were absent, increasing the combustion efficiency and flame spread rate. The presence of sidewalls increased the flame heights and reduced the heat loss to the sides.
In the other part, the wide effect was investigated on PMMA slabs with wind speed of 0, 0.5 and 1 m/s and horizontal wind oriented 30, 60 and 90 degree from the sample surface. Flame height, flame horizontal length, pyrolysis height and heat flux were measured. The results show that the external wind extended the flame upwardly and horizontally, reducing the flame thickness and consequent flame feedback. When external wind was involved in the burning, the cooling effect was strong in the early stage of fires, reducing flame spread rate. However, the involvement of wind contributed to burning when the fires grew. Additionally, the volatiles were blown downstream to extend the flame size, increasing the flame spread rate with angles of 30°and 60°.
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