因工業生產型態的急遽變化，各種之化學物品大量被引用，而這些化學品通常具有高度火災、爆炸危險性或健康危害性。回顧我國過去十年之重大災害事件，不乏有傳統產業、半導體產業及化工產業發生之災害，而這些災害大多可燃氣體或有毒氣體等的大量洩漏，若引起火災爆炸後伴隨熱輻射、爆壓等能量釋放，往往造成人員、環境及工廠之重大傷害。為了減少這方面的危害，除了增加更多的安全設備外，更重要的是如何利用有效的方式，減少災害的發生或將災害減低到最小。
當輸送管線經過人煙多的地方，一旦氣體洩漏即會造成相當危險的現象，不僅包括氣體擴散後與空氣混合及流動的過程、濃度及溫度分佈，甚至可能引起氣爆，有些洩漏的氣體具有毒物質，後果更是難以想像，所以氣體洩漏與流場擴散的研究非常重要，如果能把氣體洩漏模擬程式應用在大氣氣流的分析及氣體擴散的探討，就能減低人員、公安問題及社會財產的損失。
本文建立氣體洩漏、洩爆及化學物質等危害之模式，以瞭解引發洩漏之起始條件與危險程度。本研究是採用數值模擬方法來分析流場之漏氣濃度、壓力及速度等分佈情形，分析主要在了解所有參數之影響，結果可顯示濃度分佈及危險範圍。

Thanks to the rapid development of variable production patterns of industries, many kinds of chemicals are used. But the chemicals usually come with dangers of causing fires, explosions, and harming people. In the past decade in Taiwan, these chemicals caused many serious industrial disasters. They happened not only in conventional industries but also in semiconductor and chemical industries. And most of them happened due to the leaking of flammable or toxic gases. In the situation of the outbreak of fires, explosions may occur, and they will generally bring about heat radiation, explosive pressure, and energy releasing. And all of these often harm the workers and the environment, and also bring great loss for the factories. In order to prevent the disasters, except for improving the protection and safety equipment, it’s more important to realize how to use effective ways to reduce them.

If the gas pipes pass through a densely populated area, when some toxic gas leaks, it will cause fatal dangers which result from the mixing of gas diffusion and air, the flow process of the mixture, concentration of CH4, and temperature distribution, or explosions. After that, some toxic gas with poisonous substances will be released, and it will turn out to be horrible consequences that are beyond our imagination. So it’s really important to do research on gas leaking and gas diffusion. If gas-leaking simulation is applied on the analysis of the leaking of flammable gas and gas diffusion, it’s much more possible to protect the workers from being hurt, keep public safety, and reduce the loss on the wealth of the society.

The thesis focuses on building various hazard patterns of gas leaking, gas explosions, and chemicals, etc. From all of these, the initial conditions and the degrees of dangers will be revealed. In the thesis, numerical simulation is used to analyze the density, pressure, speed of the leaking gas and all the distributions in the flow field. The major analysis is about the effects of parameter and the display of concentration distribution, and hazard range.

中文摘要.........................................................Ⅰ
目錄.............................................................Ⅱ
圖目錄...........................................................Ⅳ
表目錄...........................................................Ⅶ
符號說明.........................................................Ⅷ
第一章 緒論……………………………………………………………………….1
1.1前言…………………………………………………………………………….1
1.2 研究動機………………………………………………………………………4
1.3 文獻回顧………………………………………………………………………5
1.4 研究內容………………………………………………………………………6
第二章 甲烷（CH4）之特性..........................................7
2.1 物理狀態………………………………………………………………………7
2.2 氣爆界限………………………………………………………………………9
第三章 理論分析………………………………………………………………….13
3.1 基本假設……………………………………………………………………..13
3.2 統御方程式…………………………………………………………………..13
3.3 紊流模式……………………………………………………………………..16
3.4 混合氣體擴散………………………………………………………………..17
3.5 壁面函數探討………………………………………………………………..18
第四章 數值模擬方法...............................................19
4.1 數值模擬軟體簡介…………………………………………………………..19
4.2 SIMPLE演算法則 ………………………………………………………….20
4.3 上風差分法…………………………………………………………………..22
4.4 鬆弛因子與離散化……….………………………………………………….24
4.5 物理幾何模型………………………………………………………………..26
4.6格點系統……………………………………………………………………...29
第五章 數值模擬結果...............................................34
5.1氣體洩漏流場之模擬………………………………………………………...34
5.1.1 邊界條件設定 …………………………………………………….......34
5.1.2 結果與討論..………………………………………………………......34
5.1.3 氣體洩漏之濃度場分佈…………………………………………........36
5.1.4 結果與討論………………………………………………………........37
5.2 不同風速之影響……………………………………………………………..41
5.3氣體洩漏流量變化之影響…………………………………………………...50
5.4不同物理特徵模型之影響…………………………………………………...59
5.5氣體洩漏之危險範圍………………………………………………………...62
第六章 結論與建議 ................................................66
6.1 結論…………………………………………………………………………..66
6.2 建議…………………………………………………………………………..67
參考文獻 ……………………………………………………………………….68

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