臺灣博碩士論文加值系統

本文採用實驗分析方法，系統性地變化鈍體尺寸與燃燒器出口條件，研究雙噴流圓盤鈍體燃燒器尺度大小對後方非預混火焰結構之效應。藉由中心燃料噴流與外環空氣噴流之出口速度、動量與質量流率的調整，建立不同阻塞比之火焰模式分區圖，並且成功地應用Schlieren光學系統、溫度量測系統、雷射都卜勒測速儀(LDV)及平面雷射誘發螢光質譜儀(PLIFS)，探討空氣環流阻塞比(BR)、雙噴流出口速度比(γ)、動量比(MR)及質量流率比(QR)等控制參數對流場結構、熱結構與反應結構之影響。
尾流火焰結構之觀察顯示，較大的阻塞比可延緩火焰跳脫現象的發生，但阻塞比太大時，其延緩能力反而變得不穩定；當中心噴流出口速度(動量)固定時，阻塞比愈大，跳脫火焰因空氣環流出口速度(動量)增加所導致的吹熄現象愈不易發生。然而，當中心噴流質量流率固定時，阻塞比愈大，跳脫火焰因空氣環流出口質量流率增加所導致的吹熄現象反而容易產生。
尾流火焰之流場特性研究顯示，雙噴流鈍體燃燒器尾流場之流場結構可區分成五種典型的模態：分別是(a) ADV模態：迴流區流場結構由ADV (air-driven vortex)所主導；(b) A-FDV模態：流場結構由ADV與FDV (fuel-driven vortex)共同控制；(c) F-ADV模態：流場結構由FDV與ADV所共同主導，且中心噴流已穿透迴流區；(d) E-ADV模態：迴流區流場結構由中心噴流攫取效應(entrainment)與ADV共同主導；(e) HE-ADV模態：流場結構仍由中心噴流攫取效應與ADV主導，但由於中心噴流之高剪應力(high shear stress)作用增強，迴流區尺寸明顯變小。
阻塞比太小時，外環空氣之迴流能力較弱，易導致空氣主導渦漩受中心噴流牽引而拉長；較大阻塞比時，迴流區之無因次軸向高度受出口動量比主導，與阻塞比無關，但流場結構則隨阻塞比不同而有所改變；對於中心噴流主導火焰(F-ADV模態與E-ADV模態流場)，固定出口動量比時，較大的紊流強度皆集中分佈於中心線兩側，其強度隨著阻塞比增加而遞減；無因次雷諾應力的正極值亦分佈於中心線兩側，與紊流強度分佈趨勢一致，但其負極值則分佈於空氣主導渦漩外側剪流層，與紊流強度分佈趨勢相反。
尾流火焰之熱與反應結構研究顯示，在ADV模態流場，氫氧自由基螢光強度分佈與溫度分佈極為吻合，侷限於迴流區內，但較大的OH基強度是沿著空氣迴流渦漩剪流層分佈；A-FDV模態時，較大的OH基螢光強度分佈於迴流區域內之右側、FSP (forward stagnation point)上游之中心噴流兩側及FSP下游之中心線區域，最大反應強度發生於空氣主導渦漩內側剪流層與中心線交會處，與高紊流強度分佈一致；F-ADV模態流場，主要反應區的位置與A-FDV模態者類似，但中心線區域之OH基螢光強度增強許多，顯示富油燃燒反應時，較大的紊流強度可增加燃燒反應。此流場之高溫區域正巧分佈在高OH基螢光強度範圍的兩側，顯示熱結構與反應結構有密切的關聯；在E-ADV模態時，由於中心噴流速度增加，燃氣混合的滯留時間變短，降低反應能力，使得中心噴流上的OH基螢光強度減弱；在HE-ADV模態時，隨著中心噴流攫取效應增大，反應強度會逐漸減弱並往迴流區上游推進，熱結構與反應結構分佈位置趨於一致。
在相同速度比下，雖然空氣外環流速度一樣，但阻塞比較大時，其空氣渦漩逆流動量反而較小，使得朝鈍體表面逆向前進的迴流渦漩，易受中心噴流的強力吸引而轉向往下游而去。因此，反應區域向流速較慢、滯流時間較長的迴流區上游推進，高溫也因而在此產生；此外，在迴流區內較大的OH基螢光強度分佈與高紊流強度分佈之間，阻塞比愈小時兩者相關性愈大，但較大的OH基螢光強度分佈與高溫分佈範圍，則隨著阻塞比增大而更趨於一致。
對不同的阻塞比，其OH基螢光分佈位置與反應強度隨著速度比而變遷的趨勢皆相同，但是當阻塞比愈大時，此現象也愈顯著；OH基螢光分佈範圍與反應強度亦會隨著質量流率比而改變，但其遷移的趨勢則隨著阻塞比增大而變得較緩和。當出口速度比固定時，動量比會隨著阻塞比增大而提高，但當質量流率比固定時，動量比反而會隨著阻塞比增大而降低。由此顯示，阻塞比、速度比與質量流率比皆為影響氫氧自由基反應區域遷移與反應強度改變之重要因素，但其背後主導的控制參數則為動量比值。

目 錄
頁次
摘要 i
誌謝 iv
目錄 v
圖表目錄 viii
符號說明 xvii
第一章 前言 1
1.1 研究動機 1
1.2 文獻回顧 4
1.2.1 迴流區特性 4
1.2.2 流場結構分析 5
1.2.3 燃燒反應對流場特性之影響 7
1.2.4 火焰型態與燃燒場特性 8
1.2.5 大尺度渦漩結構對混合之作用 9
1.2.6 雷射誘發螢光法之應用 11
第二章 實驗裝置與方法 15
2.1 實驗裝置 15
2.1.1 測試區與供氣系統 15
2.1.2 流場觀測系統 16
2.1.3 速度量測系統 17
2.1.4 溫度量測系統 22
2.1.5 氫氧自由基平面雷射誘發螢光系統 23
2.2 實驗方法 30
2.2.1 火焰影像觀察 32
2.2.2 速度場量測 32
2.2.3 溫度場量測 34
2.2.4 平面雷射誘發螢光影像觀察 34
第三章 尾流火焰結構之觀察 37
3.1 火焰型態變化 37
3.2 火焰型態分區圖 39
3.3 Schlieren 影像分析 42
第四章 尾流火焰之流場特性 44
4.1 固定阻塞比之燃燒流場特性 45
4.1.1 燃燒流場結構 45
4.1.2 燃燒流場之紊流性質 48
4.2 固定速度比之燃燒流場特性 55
4.2.1 燃燒流場結構 55
4.2.2 燃燒流場之紊流性質 57
4.3 固定動量比之燃燒流場特性 59
4.3.1 燃燒流場結構 59
4.3.2 燃燒流場之紊流性質 60
4.4 固定質量流率比之燃燒流場特性 61
4.4.1 燃燒流場結構 61
4.4.2 燃燒流場之紊流性質 63
第五章 尾流火焰之熱與反應結構 66
5.1 固定阻塞比之溫度場與反應結構分析 66
5.1.1 平均溫度與溫度擾動量分佈 66
5.1.2 燃燒反應強度分佈 70
5.2 固定速度比之溫度場與反應結構分析 74
5.2.1 平均溫度與溫度擾動量分佈 74
5.2.2 燃燒反應強度分佈 75
5.3 固定動量比之溫度場與反應結構分析 78
5.3.1 平均溫度與溫度擾動量分佈 78
5.3.2 燃燒反應強度分佈 79
5.4 固定質量流率比之溫度場與反應結構分析 80
5.4.1 平均溫度與溫度擾動量分佈 80
5.4.2 燃燒反應強度分佈 81
第六章 結論與展望 84
6.1 結論 84
6.2 未來展望 88
第七章 參考文獻 90
作者簡歷 197
著作目錄 199

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