在能源日益匱乏的今天，多重混合燃料的使用已漸漸成為了不可或缺的重要一環，因此在最近的研究當中，混合燃料時常被當作探討的主題。而在氣態的混合燃料方面，氫氣、一氧化碳與甲烷則是最主要且常見的組成物。其中之前的研究結果顯示一氧化碳與甲烷混合燃料在固定當量比下，改變燃料比例會有遠高於個別燃料火焰速度的混合燃料火焰速度極大值發生的特性最為特別，而且相當多文獻也指出添加氫氣於燃料中會明顯提升火焰速度同時增進火焰的燃燒穩定性。因此在本研究中擬以當量比1的條件下，利用實驗與數值計算的方法探討氫氣加入一氧化碳與甲烷混合燃料對其燃燒特性與火焰結構造成的影響。
首先從層流燃燒速度計算的結果顯示，當氫氣加入總燃料的比例增加至50%時，除了整體燃燒速度提升之外，最大火焰速度發生的一氧化碳與甲烷比例也會從80%一氧化碳與20%甲烷轉變為100%一氧化碳。而藉由預混對衝流火焰的實驗與Chemkin collection 3.5搭配GRI －Mech 3.0的計算結果亦證實了此特性。其中當氫氣佔總燃料10%與20%時，最大火焰速度發生的比例分別為90%一氧化碳與10%甲烷、94%一氧化碳與6%甲烷。
而從火焰結構的分析結果也證實了氫氣的加入對火焰速度變化的影響一樣是來自主要化學機構路徑的轉變所造成。雖然最大火焰速度發生的一氧化碳與甲烷比例因氫氣的加入有所改變，但在各自火焰速度最大發生的比例下，一氧化碳快速氧化反應式（R99）的反應速率依然會達到最高，並提供了主要且大量的熱釋率。然而較不同的是，氫氣氧化反應式（R84）的反應發生位置、反應速率及熱釋率都會因氫氣的增加而超越甲烷的氧化反應式（R98）。靈敏度分析結果則顯示氫氣的加入並不影響反應步驟上重要性的改變過程，其重要性最為重要的反應步驟皆在80%一氧化碳時由鏈鎖反應（R38）轉變為一氧化碳快速氧化反應（R99）。

As the turn of the new century, energy crisis and global warming have become important and urgent issues threatening the human beings and modern civilization. The supply of energy resources falls short of rapidly growth of demand. For all the efforts to partly relieve the coming energy crisis, the use of blended fuels has been proposed and becoming one of the important methods. For the gaseous blended fuels, gasified fuels from biomass and low-grade coals, with H2,CO, and CH4 as the primary compositions, attract intensive research attentions recently. In the present study, the blended fuels have also been the subjects for researches, and From the previous results reported by our group, it has been shown that the maximum laminar burning velocity for the CH4/CO blended fuels varies with the ratio of the fuel components at the same equivalence ratio, and the maximum burning velocity for the blended fuels far exceeds the burning velocity for each individual component. Also, extensively reported in the literature that addition of small amount of hydrogen in fuel will generally increase its burning velocity apparently. Therefore, in this study, the effects of H2 addition in stoichiometric CH4/CO blended fuels on the resultant combustion characteristics and flame structures for are investigated by experiments and numerical simulations.
Numerical prediction results of the laminar burning velocity for CO/CH4/H2 blended fuels in stoichiometric condition reveal that not only all the laminar burning velocity is increased with H2 addition, but also the CH4/CO fuel ratio of the maximum laminar burning velocity is changed from 80%CO and 20% CH4 to 100%CO when H2 addition reaches 50% of the total fuel amount. This finding is validated by both numerical simulations using Chemkin collection 3.5 with GRI-Mech 3.0 and experiments using the premixed H_2/CH_4/CO/Air opposed-jet flames. When 10%H2 and 20%H2 are used in the H2/CH4/CO flames, the CH4/CO fuel ratio of the maximum burning velocity varies from 90%CO and 10% CH4 to 94%CO and 6% CH4 respectively
Based on the analysis of flame structures, it’s shown that the variation in burning velocity with H2 addition isprimary due to the transition of dominant chemical kinetics paths. Although the CH4/CO fuel ratio of maximum laminar burning velocity is varied with H2 addition, the reaction rate of CO fast “wet” oxidation（R99）is still dominant as the major contributor in the sensitivity study, and CO fast oxidation（R99）provides primary and most heat-release rate. However, it becomes different that the reaction rate of H2 oxidation（R84）exceeds CH4 oxidation（R98）in the position where major oxidation happens in terms of reaction rate, and heat-release rate as the concentration of H2 addition is increased. Finally, The results of sensitivity analysis also shows that the variation of the importance in reaction steps is not affected by H2 addition, and the most important reaction step is changed from the chain-branching reaction（R38）to the reaction of CO fast oxidation（R99）when CO in CH4/CO is increased to 80%.

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