本研究主要是利用實驗搭配模擬當二氧化碳在純氧條件下對於微管道的觸媒效應之影響。由於純氧燃燒當二氧化碳取代氮氣會因為二氧化碳比熱為氮氣1.66倍，此外從化學角度去觀看反應式CO2+H ->CO+OH，之反應為大量吸熱反應，導致火焰的不穩定性，以及純氧燃燒的氧氣來源需要另外耗能提供，而且微小化過程所造成面體比(surface-to-volume ratio)增加與混合停滯時間減少的問題，進而導致火焰冷熄現象的發生，主要包括熱能冷熄(thermal quenching)與自由基冷熄(radical quenching)。目前純氧燃燒的結果都顯示，在CO2迴流環境下氧氣比例通常需要提高到約30%才能穩定穩駐火焰，對於純氧燃燒的推動相當不利。
因此吾人採用微管道中披覆觸媒並搭配不同觸媒配置與空腔設計進而誘發氣相化學反應與壁面化學反應，得以增加燃料轉化率。實驗結果顯示，燃料為氫氣、當量比0.6且流體速度為10m/s時，分段式觸媒搭配空腔可以維持氣相反應於氧氣濃度為23%的純氧條件，因此觸媒與空腔及其搭配確實可以有效降低所需的穩駐火焰的氧氣比例。另外從模擬可看出CO的來源大都來自於氣相反應，而當CO接近觸媒壁面時很容易被觸媒吸附並反應成CO2增加熱釋率，因此觸媒有助於較低的氧氣比例下去穩駐火焰，而且尾氣CO2濃度的提升，也有助於CO2捕捉。

In this study, the effect of carbon dioxide on catalyst reaction in a small-scale channel in oxy-fuel atmosphere is investigated through experiments and numerical simulation. In the oxy-combustion, carbon dioxide in the flue gas is usually recirculated to dilute the oxidizer stream to reduce the flame temperature. However, the specific heat of carbon dioxide is relatively higher than that of nitrogen, and it causes significant reduction of flame temperature and combustion stability margin. Furthermore, carbon dioxide in the flame does not only act as an inert diluent, but also involve in flame reactions and modifies flame behavior and combustion characteristics. The chemical reaction CO2+H -> CO+OH usually found in the flame is a large endothermic reaction step and may cause combustion instability if its reaction rate is altered by CO2 addition. During the miniaturization, the surface-to-volume ratio of the combustion chamber will be increased and the mixing and reaction residence time will be decreased. It causes flame quenching, such as thermal quenching and radical quenching.

Consequently, various flame enhancing and flame stabilization techniques for micro-scale combustors have been proposed, among these techniques the catalyst bed configuration of segmented catalyst with cavity in a micro-channel is expected to induce gas reaction and surface reaction simultaneously, and enhance fuel conversion. The experimental results of the segmented catalyst with cavities show the improvement of oxy-combustion behaviors in a micro-channel by reducing the requirement of excessive oxygen concentration in the oxidizer stream for flame stability. When the flow rate is 10 m/sec and corresponding equivalence ratio of 0.6, oxy-hydrogen combustion in a micro-channel can be stabilized in a condition of 23% oxygen concentration in the oxidizer stream. The simulation results also show that the carbon monoxide generated in gas reaction can be oxidize to carbon dioxide by surface reaction and release heat. Using catalyst, the oxy-combustion can be stabilized in a condition of lower oxygen concentration.

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