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Sustainable Energy 2024
NH3/CH4混合燃料层流火焰速度的数值分析及其反应机理的优化
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Abstract:
NH3作为一种无碳燃料，且具有较长的应用历史、较高的市场成熟度和较完整的产业链，因此在推动全球低碳发展中具有很大的发展前景。为了解决NH3在燃烧时火焰传播速度较慢的问题，可行的方法是将NH3与CH4混合燃烧。针对NH3/CH4混合燃烧的数值模拟研究时采用的反应机理比较多样且都存在相对误差的问题，对NH3/CH4混合燃料的层流燃烧速度进行模拟并通过反应灵敏度等方法分析了重要影响因素。结果表明燃料CH4的添加可有效使NH3的层流火焰速度线性增加，燃烧强度显著提升。同时发现层流火焰速度在很大程度上受火焰中自由基O、H、OH数量以及基元反应H + O2 < = > O + OH反应速率的影响，随CH4加入火焰中的O、H、OH的摩尔分数也随之增大，因此进一步提高NH3的层流火焰速度。此外通过敏感性分析以及火焰结构分析发现基元反应的参数设置是各个机理模拟产生差异的根本原因，因此本研究基于模拟表现最好Okafor机理，根据其他常用机理的参数设置和实验数据形成了优化机理Okafor-Modified，与实验结果的平均相对误差在10%内。
As a carbon-free fuel with a long application history, high market maturity and a complete industri-al chain, NH3 has great development prospects in promoting global low-carbon development. In or-der to solve the problem of slow flame propagation when NH3 is burning, a feasible method is to add CH4 to NH3 for mixed combustion. In order to solve the problem of various reaction mechanisms and relative errors in the numerical simulation of NH3/CH4fule, the laminar burning velocity of NH3/CH4 fuel was simulated and the important influencing factors were analyzed by means of reaction sensi-tivity and other methods. The results show that the addition of CH4 effectively increases the laminar flame velocity and combustion intensity of NH3. At the same time, it is found that the laminar flame velocity is greatly affected by the number of free radicals O, H, OH in the flame and the reaction rate of elementary reaction H + O2 < = > O + OH, and the molar fraction of O, H, OH in the flame increases with the addition of CH4, so the laminar Burning velocity of NH3 is further increased. In addition, through sensitivity analysis and flame structure analysis, it is found that the parameter setting of primitive reaction is the fundamental reason for the differences in the simulation of various mecha-nisms. Therefore, based on the Okafor mechanism with the best simulation performance, the opti-mization mechanism Okafor-Modified is formed according to the parameter setting of other com-monly used mechanisms and experimental data. The average relative error with the experimental results is within 10%.
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