臺灣博碩士論文加值系統

本研究成功建立二維模型，並以數值方法探討甲烷/空氣預混氣體在當量比ψ=1燃燒時漸張流道中火焰行為以及火焰存在範圍。文中使用完整之Navier-Stokes方程與簡化之甲烷一步驟化學反應式，探討不同壁面溫度、入口流速、漸張角度下對火焰行為的影響。
研究發現壁面溫度600K下控制入口流速在低流速會出現穩定對稱鬱金香火焰；中流速時會出現震盪火焰；而高流速時則會出現穩定傾斜火焰，傾斜長度則會隨著流速增加，火焰前端點會隨著流速增加而向下游區移動。改變壁面溫度在低與中壁溫時，火焰型態為穩定對稱蘑菇狀與鬱金香狀火焰；高壁溫時火焰則為震盪火焰現象。由於壁面溫度與火焰之間熱耦合的作用，會影響火焰前端點停留的位置，溫度越高，火焰前端點較接近上游處。漸張角度的改變除了影響通過之質量通量，也會對流場造成改變，小角度之火焰型態為震盪；大角度(θ=5^°)時則為穩定火焰。
針對火焰震盪行為的研究中，入口流速增加會使得火焰前端點向下游區移動並增加最大火焰長度，在高流速火焰週期時間會因為火焰拉伸而變長。壁面溫度增加則是會使得火焰前端點向上游區移動，並使得火焰最大長度縮短，且發現火焰震盪週期會隨著壁溫增加而加快。在漸張角度的影響中，發現平流道與漸張流道流場性質較不相同，其火焰上下震盪較劇烈且無重複性，週期時間較短。最大火焰長度則會隨著漸張角度變大而縮短，角度則對火焰前端點則是沒有明顯影響。

In this study, the complete Navier-Stokes equations are used in the mathematical formulation and the flame combustion is modeled by a simplified single-step reaction for methane-air mixture to investigate the different parameters such as wall-temperature, inlet velocity, diverging angle, and distribution of flame behaviors.
When wall-temperature is at 600K, the steady tulip-shaped flame exists in the low-velocity region, the oscillating flame in the mid-velocity region, and the slant-shaped flame, with length increasing with velocity, in the high-velocity region. The flame front will move toward the downstream when the velocity increases. When changing the wall-temperature from low to midrange, the steady flame shape is changes from mushroom to tulip and the only to oscillating flame in the high-temperature range. Due to the thermal coupling between the wall-temperature and flame, the location of flame front moves to the upstream when wall-temperature is increased. The diverging angle of the flow channel affects not only the mass flux but also the flow field. The oscillating flame behaviors are observed in small-angle channel and steady flame behaviors in the large angle (θ=5^°) channel.
In the research of oscillating flame, increasing inlet velocity makes the flame front moves to the downstream and makes the stretching flame longer. In the high-velocity region, the period of time becomes longer due to the flame extension. The increase of wall-temperature makes the flame front moves toward the upstream, makes the stretching flame shorter and the period of time becomes shorter with the increasing wall-temperature. For the angle effects of diverging channel, the stretching flame becomes shorter with the increase in angle with less effect on the location of flame front. In addition, the oscillating flame in the parallel channel is stronger and more irregular with a short period of time.

目錄
論文審定書 i
誌謝 ii
中文摘要 iii
Abstract iv
目錄 vi
圖目錄 vii
表目錄 viii
符號說明 ix
第一章 緒論 1
1.1 本文架構 1
1.2 前言 2
1.3 微小尺度燃燒系統 3
1.3.1 微尺度燃燒之定義 3
1.3.2 熄滅方式 3
1.3.3 連續性 4
1.4 文獻回顧 5
1.5 研究目的 10
第二章 數學模型和求解方法 11
2.1:邊界條件 12
2.2模型假設與統御方程式 13
2.3:模型格點測試 16
2.4:求解方法和收斂標準 18
第三章 結果與討論 19
3.1:穩定火焰 20
3.1.1 壁面溫度對不同流速之火焰行為影響 20
3.1.2 漸張角度對不同流速之火焰形狀影響 30
3.1.3漸張角度以及壁面溫度對火焰前端點位置之影響 32
3.2:震盪火焰 33
3.2.1 震盪火焰機制 33
3.2.2 入口流速對震盪火焰之影響 41
3.2.3壁溫對震盪火焰之影響 45
3.2.4 漸張角度對震盪火焰之影響 49
3.2.5 入口流速、壁面溫度、漸張角度對火焰震盪週期之影響 53
第四章 結論與未來展望 55
參考文獻 57

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