多孔介质内预混气体燃烧稳定操作范围的研究

为优化多孔介质燃烧器设计,考察了多孔介质的物性参数对稳定燃烧速度极限的影响.建立了甲烷/空气预混气体在多孔介质内燃烧的二维数学模型,在FLUENT软件中加入自定义编程,用求解瞬态控制方程的方法对多孔介质内的稳定燃烧进行计算,考察了当量比、多孔介质的辐射衰减系数及导热系数对速度极限的影响.结果表明,当量比从0.55增加到0.9时,速度的最小和最大极限值有明显增加,稳定燃烧的最大与最小速度极限差从0.12增加到0.72;与参考算例相比,当下游区域导热系数增加5倍而上游导热系数保持不变时,稳定燃烧最大与最小速度极限差增加到0.47;上游多孔介质的辐射衰减系数增加而下游辐射衰减系数保持不变,可以达到相对最大的稳定操作范围.

Study on Stable Operation Range of Premixed Gas Combustion in Porous Media Burner

The combustion of methane/air mixture in a two-section porous burner was numerically simulated for the optimal design of a porous media burner. The software FLUENT with self-designing codes was used to solve a two-dimensional transient mathematical model of the combustion. The effects of the parameters, such as equivalence ratio, radiative extinction coefficient and thermal conductivity of the porous media on the range of stable burning rate were investigated. The results showed that the difference of maximum and minimum limits of burning rate enlarges from 0.12 to 0.72 when the equivalence ratio increases from 0.55 to 0.9 and the maximum and minimum limits of burning rate both increase obviously. Compared with the reference example, if the downstream thermal conductivity is 5 times greater than its original value and the upstream thermal conductivity remains unchanged, the difference of maximum and minimum limits of burning rate reaches 0.47. It was found that the radiative extinction coefficient of upstream section increases but that of downstream one remains unchanged, a relatively biggest stable operation can be provided.