- 學位論文
複燃影響因子之探討分析
The Exploration to the Factors of Backdraft Scenario
摘要
本研究包含不同開口模擬情境之複燃實驗、實驗箱內部設置阻礙物以及細水霧系統對複燃情境之影響變化，變化細水霧系統之流量及噴頭，探討不同細水霧放射模式及流量，對於複燃現象之抑制及降低複燃發生之可能性變化。 在立即點火之實驗中，開口面積增大，會使得空氣進入空間置換量增加，加速降低燃料濃度，亦加快複燃產生之時間，且無法有效建壓，故複燃壓力值較小，且當複燃發生時，發現不論距離點火源最近或最遠處，其溫度皆大於60℃，顯示複燃瞬間所製造之高溫將造成未穿著任何防護設備之人員嚴重損傷。 利用機械送風進行一系列之複燃實驗所求得之預測公式，可用來預測空間殘存之燃料量在多大的風速下可產生最大複燃壓力，風速(m/s) = 9×10^(-05)× 燃料量(%)^(3.4)。設置阻礙物於實驗箱中，確實會因亂流而使得複燃壓力波增強，在氣流遇上阻礙物時，會使內部產生亂流，使空氣與燃料量混合越均勻，所引發之複燃壓力波也越強烈，但僅於單開口情境下；若開口面積增大時，則因建壓不易而無法產生強烈壓力波；開口情境為影響複燃壓力波強弱之重要因素。 經由實驗數據得知，發現設置於內部可有效抑制複燃，並且由實驗結果得到抑制複燃之臨界細水霧量預測公式，細水霧百分比(%) =0.0113×燃料量百分比(%)^2-0.0556×燃料量百分比(%) +0.0494，以此預測公式來預估臨界抑制複燃之細水霧量。
並列摘要
This research focuses on the effects of the opening, obstacles, and water mist in the backdraft scenarios. Through the larger opening, the more entrained air causes fast backdraft scenarios, but builds smaller pressure in the tests. The temperature was found over 60℃ in every measured point and people will get hurt in such high temperatures without protective gear. A correlation is obtained based on different air velocities flowing into the container and the initial fuel amount in it. The turbulent induced by the obstacles inside the container carries more uniformed fuel-air mixture and causes higher b pressure. For the larger opening, the backdraft pressure is still small in the container with obstacles because it’s hard to build pressure in such a larger opening. More water mist can inhibit backdraft scenarios when discharged inside the container before the opening is opened to entrain the air into the container. A correlation is obtained to predict the inhibited amount of water mist as follows: water mist percentage = 0.0113 × (fuel percentage)^2 – 0.0556 ×(fuel percentage) ＋ 0.0494.