臺灣博碩士論文加值系統

本論文主要以數值方法來模擬地下車站架設消防撒水系統所造成的溫度、能見度、一氧化碳濃度變化，並改變水量、粒徑、排風機風量，探討這些參數之改變對車站發生火災時所造成的影響。本文採用計算流體力學軟體FDS來進行計算，模擬模型藉由實際施工平面圖來建立，並利用防煙垂壁區分各個火場區塊進行探討，網格則採用六面體網格將計算區域離散化，數目約70萬。火源大小的確立是參考文獻中提及，平均一人可攜帶20公升之汽油，其六分鐘內燃燒完成之熱釋放率為3.6MW；風機開啟時機，採用定址偵煙光電式偵煙探測器，並設定其偵測到能見度低於20公尺時開啟；撒水器作動時機為撒水器位置偵測到溫度大於68℃時。結果顯示，改變撒水器參數皆不會影響排煙系統開啟時間；改變撒水器水量時，水量增加降溫效果越好，且由偵測點數據顯示80LPM為48.1℃、100LPM為46.7℃、120LPM為45.1℃，但水量過大可能會產生水害，對後續復原造成難度。噴霧粒徑的大小主要影響的因素是水滴的蒸發速率，粒徑越大吸熱速度較慢，其火場升溫會比較快，400μm為49.1℃、100μm為48.1℃、50μm為47.5℃，雖然粒徑越小降溫效果越好，但其噴嘴成本高，因此需要考量成本問題。改變排風量則是最有效增加能見度、降低高溫濃煙累積與降低一氧化碳濃度的方式，火場溫度在排風量30CMS為42.0℃、60CMS為38.8℃、90CMS為35.5℃，且每增大30CMS約可增加30秒的逃生時間，但若無限制的加大排風量是否會造成其他影響還需進一步討論。

The purpose of this study is to simulate the effect on changes of temperature and visibility and Carbon monoxide concentration which coursed by sprinkler system in underground station by numerical method. Besides, change water quantity, particle diameter , exhaust airflow to investigates the changes of variable of the influences in underground station fire. This study adopted Computational fluid dynamics software FDS. The simulated model is built from the real construction plan and utilize smoke barrier to separate the fire district. Besides approximately 700,000 Hex Mesh are used to calculate the discrete fire area. The size of fire is referred to the reference, one person can carry 20 liter of gas which the rate of heat release is 3.6MW within six minutes. The moment to be set to turn on the Blow is when the Addressable Photoelectric Smoke Detector’s visibility is deteriorated below 20m. Moreover, when the sensor detect the temperature higher than 68℃, sprinkler will be turned on. The result shows that the variable of sprinkler’s changes do not influence the time to turn on the exhaust system. When the sprinkler’s water quantity increase, the effect of cooling is better. According to the data of sensor shows that 80LPM is 48.1℃, 100LPM is 46.7℃and 120LPM is 45.1℃. However, excessive water quantity may cause flood and hard to repair. The size of spray particle is mainly influenced by rate of water evaporation. The bigger particle slow down the rate of heat absorption which caused the temperature rise rapidly in fire. 400μm is 49.1℃, 100μm is 48.1℃and 50μm is 47.5℃. Although the small particle’s effect of cooling is better than big one, the nozzle, spray small particle, cost more money. So the costs need to be considered. By changing amount of exhaust airflow is the most effective way to increase the visibility, reduce amount of high temperature smoke and Carbon monoxide concentration. The relationship between amount of exhaust airflow and fire field temperature are: 30CMS is 42.0℃, 60CMS is 38.8℃and 90CMS is 35.5℃. Moreover, increasing 30CMS approximately create 30 seconds to escape. However, it need to investigate more that unlimited increasing exhaust airflow whether cause other influences.

摘 要 i
ABSTRACT ii
致 謝 iv
目 錄 v
表目錄 vii
圖目錄 viii
第一章 緒論 1
1.1 研究動機與目的 1
1.2 文獻回顧 2
1.3 研究方法 4
1.4 論文架構 5
第二章 理論分析 6
2.1 火源發展趨勢與設計 6
2.2 煙層流動特性 8
2.3 撒水頭的作動原理 9
2.4 水顆粒之狀態變化 11
2.5 撒水器之水滴軌跡 12
2.6 撒水器之水滴熱傳方程式 15
第三章 CFD模擬理論 17
3.1 FDS數值方法與架構 17
3.2 FDS之守恆方程式 19
3.3 FDS之熱輻射模式 21
3.4 FDS之燃燒模式 22
3.5 FDS之熱邊界條件 24
第四章 物理模型設定 26
4.1 車站建模 26
4.2 火源熱釋放率與位置設定 33
4.3 排煙系統與撒水頭設定 34
4.4 網格獨立性測試 38
4.5 自然對流對車站之影響 39
第五章 結果與討論 40
5.1 有無裝設撒水器結果分析 41
5.2 改變流量結果分析 45
5.3 改變粒徑結果分析 51
5.4 改變排風量分析 57
第六章 結論與建議 62
6.1 結論 62
6.2 建議與未來展望 64
參考文獻 65
符號表 68

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