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研究生:李介佑
研究生(外文):Jie-You Li
論文名稱:數值方法探討無重力下火焰在極薄固體燃料的傳播
論文名稱(外文):Numerical simulation of Flame Spread over Extremely Thin Solid Fuel in microgravity
指導教授:許聖彥
指導教授(外文):Sheng-Yen Hsu
學位類別:碩士
校院名稱:國立中山大學
系所名稱:機械與機電工程學系研究所
學門:工程學門
學類:機械工程學類
論文種類:學術論文
論文出版年:2019
畢業學年度:108
語文別:中文
論文頁數:83
中文關鍵詞:強制對流無重力極薄固體燃料順流反轉傳播火焰面積密度
外文關鍵詞:forced flowmicrogravityextremely thinconcurrent-reversed flamearea density
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本研究以二維火焰傳播模型探討無重力強制對流場下,火焰在極薄固體燃料上的傳播現象。研究使用兩種不同數值模型,分別探討火焰點燃、成長至傳播的過程,以及火焰在穩定傳播下的形狀與特性。研究發現,在無強制對流的情況下,火焰仍可在極薄燃料上傳播,導致火焰在順流流場下,有兩種火焰形態:順流傳播火焰(Concurrent-flow spread flame)以及順流反轉傳播火焰(Concurrent-reversed spread flame)。順流傳播火焰發生在當強制對流比火焰傳播速度快時,火焰基部在上游燃料燃燼區,而火焰尾端會覆蓋下游區燃料;而順流反轉火焰則發生在強制對流速度比火焰傳播速度還要慢時,其火焰基部會在較下游的燃料表面,而火焰尾端則在燃料的上游端,其形狀與逆流傳播火焰(Opposed-flow spread flame)類似。另外,在火焰點燃、成長的過程中,順流火焰會形成二個火焰區,此乃因為火焰傳播速率快,下游端氧氣仍有充足的氧氣與燃料反應。然而當火焰成長至穩定傳播時,上游端氧氣完全消耗,以及反應生成物 (H2O、CO2) 的累積,導致下游氧氣不足,下游端反應區消失。此外,研究也發現火焰傳播速度隨著面積密度變小呈現指數性的上升。
In this study, the two-dimensional flame spread over extremely thin solid fuel (ρ_α<1 mg/cm^2) is investigated in forced flow without gravity. There are two numerical models. One is utilized to simulate the flame spread from igniting to spread, and the other is utilized to simulate flame structure in stable state. In stable state, flame can spread without forced flow, which causes two types of flame structures in concurrent-flow spread flame. When the velocity of forced flow is faster than the flame spread rate, flame base would be at the upstream of solid fuel, and flame tip would cover the downstream of solid fuel. The flame structure described above is called concurrent-flow spread flame. When the velocity of forced flow is slower than the flame spread rate, flame base would cover the surface of solid fuel, and flame tip would be at the upstream of solid fuel. The flame structure described above is called concurrent-reversed flame and that flame structure is similar to opposed-flow spread flame. Besides, there are two flame zones in concurrent-flow spread flame, because the flame spread rate is rapid, and there exists sufficient oxygen at downstream which is enough to be reacted with fuel. However, when flame develops to stable spread, oxygen has been consumed completely and some productions have accumulated (H2O, CO2), the flame would disappear due to lack of oxygen. When flame spreads over extremely thin solid fuel, flame spread rate grows exponentially as the area density gets smaller.
摘要 ii
Abstract iii
目錄 v
圖目錄 vii
表目錄 x
符號說明 xi
1. 序論 1
1.1前言 1
1.2文獻回顧 1
1.3研究目的 5
2. 數值模型 6
2.1 統御方程式 7
2.2 邊界條件 10
2.3 物理性質 11
2.4 網格繪製 16
3. 模擬結果 18
3.1火焰發展傳播模擬與實驗比對 19
3.2 穩定火焰傳播 29
3.2.1穩定火焰傳播的火焰形狀 29
3.2.2 強制對流對穩定火焰傳播的影響 34
3.2.3 面積密度對火焰傳播的影響 37
3.2.4壓力對火焰傳播的影響 41
4. 結論 44
參考文獻 45
附錄 48
有限長度30公分火焰傳播模型User defined function 48
穩態無限長度火焰傳播 User defined function 57
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