Kinetic Effects of Hydrogen Addition on the Thermal Characteristics of Methane鈥揂ir Premixed Flames

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• 作者：Qingfang Li ; Ge Hu ; Shiyong Liao ; Qian Cheng ; Chi Zhang ; Chun Yuan
• 刊名：Energy & Fuels
• 出版年：2014
• 出版时间：June 19, 2014
• 年：2014
• 卷：28
• 期：6
• 页码：4118-4129
• 全文大小：799K
• 年卷期：v.28,no.6(June 19, 2014)
• ISSN：1520-5029

文摘

A numerical investigation was implemented to evaluate the kinetic effects of hydrogen addition on the thermal characteristics of lean and stoichiometric premixed methane鈥揳ir flames, on the basis of the detailed kinetic reaction mechanism GRI-Mech 3.0. The flame temperature profiles and the distributions of reactive species were predicted as a function of flame height by solving a freely propagating laminar premixed flame model. Some global properties of the premixed flame, i.e., the flame temperature gradient, the inner layer flame temperature, and the heat release rate, were estimated. Results showed that hydrogen enrichment in methane鈥揳ir flames led to increases in the peak flame temperature, the peak temperature gradient, and the peak heat release rate, but a decrease in the inner layer flame temperature. Analyses of the interactions among heat release rates, radical production, and reaction progress rates were conducted. Analysis of the contribution of the heat release rate showed that the reactions concerning CH₃ consumption consistently released a large proportion of heat, while significant contributions were found from the reactions of OH + H₂ H + H₂O, H + O₂ + H₂O HO₂ + H₂O, and H + HO₂ 2OH, when hydrogen was added. The rates of radical production were computed on the basis of the predicted species profiles. It was suggested that OH and H were the two important radicals, which had significant relevance to the heat release in the hydrogen-enriched flame. The analyses of the formation pathway were conducted for OH and H. It was shown that radical H was mainly produced in the reactions OH + H₂ H + H₂O and O + H₂ H + OH, and the dominant reactions contributing to the production of radical OH were O + H₂ H + OH, O + CH₄ OH + CH₃, and H + HO₂ 2OH. The progress rates of these preceding reactions were compared. Numerical results indicated that hydrogen had its kinetic effects on methane鈥揳ir flames through promoting the formations and consumptions of OH and H, and the dominant reactions in terms of the contribution to heat release were OH + H₂ H + H₂O, H + O₂ + H₂O HO₂ + H₂O, and H + HO₂ 2OH.