FDS軟體對於透天厝火災模擬之差異性分析

Variation Analysis of Townhouse Fire Simulations by FDS Software

台灣因地狹人稠，人口成長迅速，導致住宅用建築物有集合化、高密度化之趨勢，早期台灣各地有許多透天厝建築物，隨著時間流逝，此種建築物設計多半顯得老舊，消防及逃生相關設備規劃不完善，若發生火災，可能造成重大之人員傷亡及財物損失。因此本研究蒐集台灣較為常見之長型透天厝模型，並使用火災動態模擬器（Fire Dynamics Simulator, FDS）軟體對該種透天厝進行火災模擬，並分成下列項目：不同的燃燒方式、FDS版本差異性及固／液／氣三態火源等，來進行火源延燒探討及差異性分析比較。由於三態火源之熱釋放率均不相同，因此另外設置小模型並且假定其為相同熱釋放率以進行比較。由模擬結果顯示：以Material Reaction方式設定之物件燃燒無法使火焰產生延燒效果，如要觀察火災之火焰延燒現象，建議使用Surface Reaction。由氣態火源模擬結果之火焰分布、溫度剖面分析及煙流濃度分析得知，早期FDS 4之溫度及燃燒物種在建築物內部會有流失較快的情況，並由FDS 5之內部絕熱效果可看出得到改善。在固態火源燃燒方面，FDS 5會有溫度上升較快及物種產生較少的情況，可由FDS 6之模擬改善其物種以便得到相對應的控制。在液態火源燃燒方面，由模擬結果推論在早期FDS 5之液態火源較近似於氣態火源燃燒，此點可由燃燒結果及運算器之運算速率比得知，在FDS 6中由於加入液態蒸發的燃燒熱運算，所以其液態燃燒較接近真實的燃燒結果，但其運算速度也較固態及氣態為慢。由小模型的測試結果顯示，在相同熱釋放率下，三態火源之燃燒結果差異不大，但運算時間則以液態火源較久。 Taiwan is a densely populated island and its urban population is growing rapidly to result the phenomena of aggregated, high density, diversified and with complex equipment within the buildings. There are many townhouses in the early days of Taiwan; however, the design of these buildings are out of date and their fire prevention plans are not complete with the evolution of times. Heavy casualty and property loss may happen once a fire broke out. The most common type of townhouse is the long-type. This study collects the commonly seen long-type townhouse model and employs the open published Fire Dynamics Simulator (FDS) software to implement the fire simulation of the townhouse model. The extended burnings are discussed according to the following items: the burning status of the three-state fire, comparisons of different FDS versions, and differences analysis in different combustion modes. In addition, since the heat release rates of the three-state fire source are not the same, we employ a small model to observe the three-state fire source with same heat release rate. The results show that the extended burnings effect isn't shown up by using the Material Reaction object. Instead, it is recommended to use the Surface Reaction setting to observe the extended burnings result. According to the results of flame distribution, temperature profile analysis and smoke flow concentration analysis of the gaseous fire source simulation, it shows that the temperature and the burning species in the early FDS 4 have the conditions of losing too fast inside a building. These drawbacks have been improved by the internal thermal insulation effect of the FDS 5. As for the solid-state fire source burning results, the temperature rising too fast and the burning species generated too low in the early FDS 5. By improving the characteristics of the species, all these have been controlled accordingly in the FDS 6 simulation results. The simulation result of liquid-state fire source combustion confirms that the liquid-state fire source in the early FDS 5 version is closer to the combustion result of the gas-state fire source, which can be proved by the combustion result and the computational speed ratio. By adding the combustion heat calculation of liquid evaporation in the FDS 6, its liquid-state combustion result is closer to the real one; however, the corresponding calculation speed is also slower than that of the solid- and gas-state. All three-state combustion results do not show much difference while maintain at the same heat release rate.