本文主旨為探討多環燃燒器之火焰交互作用及最佳性能設計，透過數值計算(CFD-RC)與實驗量測溫度、流場結構(PIV)與污染物等方法，探討環間距比(S/d)與燃料當量比(□)所產生之不同火焰交互作用對其燃燒性能之影響。分析結果發現，多環燃燒器的幾何突張結構所形成之駐焰效果及環與環間的預熱效果，皆可提供燃燒器在貧油條件下穩定操作，利用此特性設計出多環燃燒器之最佳操作參數S/d = 1.67、□□值內環為0.8、中環為1.1、外環為1.1，其特性已達高效能、低污染之目標。
研究結果顯示，當改變環間距比時，對於燃燒場內流場結構的影響甚大，故產生不同程度之火焰交互作用；當S/d = 1.0時，其環間距相對較小，造成各環之預混火焰無法形成獨立環狀火焰，降低其火焰反應面積，且無法提供出口端附近未燃氣的預熱，對於火焰燃燒速率無法有效的提升，在污染物方面，雖然二氧化碳的生成量相對較低，但氮氧化物的生成量卻最高；在S/d = 1.67與2.33的條件下，由於環與環之間的距離增加，故皆能產生獨立環狀火焰結構，且火焰模態相當類似，在氮氧化物的排放量，其表現的性能也不相上下，原因為當環間距比增加到某一程度後，環間距比的改變效應迅速降低；不同的燃料當量比有不同之火焰初始強度與特性，亦影響火焰交互作用，當□□值為1.1時，火焰初始強度相對最強火焰溫度也最高，雖然氮氧化物的生成量略高，但評比各項數據後，其整體性能優於□□值為1.3與□□值為1.5。

The objective of this study is to investigate the flame-interaction and to design a multi-ring combustor with optimal performance. The flame-interaction was controlled by varying gap ratio (S/d) and equivalence ratio (□). Their effects on the flame structure were investigated by numerical and experimental methods. The sudden expansion structure of multi-ring combustor generate the flame holding and preheating effect, these phenomena can provide combustor operate in the fuel lean condition. The optimal operation conditions are S/d = 1.67, the inner ring □ = 0.8, and the middle and the outer ring □ = 1.1, which is corresponded to the objective of high performance and low pollutant.
The change of geometric dimension by varying S/d greatly affects the flame structure, where different degree of flame-interaction can be found. When S/d = 1.0, the flame merge together because the gap distance is short, and the separated ring-flame cannot be observed. This phenomenon will cause decrease reaction area and the preheating effect can not be provided to unburnt gas near the exit region of the combustor. Thus, the combustion rate can not be improved effectively. Considering the emission production, despite the production of carbon dioxide is lower, the production of nitric oxides(NOx) is the highest. When S/d = 1.67 and 2.33, a separated ring-flame can be found on each of the rings since the gap distance is wider. Similar flame pattern can also be found among ring-flames. Furthermore, their productions of NOx are nearly equal. This is because the effects of flame-interaction on flame structure rapidly decrease when the gap ratio increases beyond a specific value. The equivalence ratio dominates the initial flame strength and characteristic; consequently, it influences the flame-interaction. When □ = 1.1, the flame strength is the strongest and temperature is the highest. Although the production of NOx is slightly higher than that of □ = 1.3 and □ = 1.5, its global performance is the best.

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