泡沫陶瓷材料及其微观结构参数对多孔介质燃烧特性的影响

基于Kelvin模型,建立了泡沫陶瓷多孔介质的微观结构参数(孔筋长度、孔筋半径、微立方体节点边长)与其孔隙率、导热系数等宏观特性参数的关系式;利用FLUENT软件,就材质种类及其微观结构参数对双层多孔介质燃烧器内甲烷/空气预混燃烧性能的影响进行了数值模拟。结果表明,在入口速度为60cm/s、当量比为0.6的条件下,燃烧区材质为SiC时,气、固相温度最高,稳定操作范围以SiC、ZrO2、Al2O3的顺序依次降低;无量纲参数d(微立方体节点边长与孔筋长度之比)的增加会降低气、固相温度且会改变火焰面驻定的位置,而e(孔筋半径与孔筋长度之比)的改变对气、固相温度分布影响不大。因此,在实际燃烧器多孔材料选型中,应优先考虑微观结构中微立方体节点边长和孔筋长度的合理选择。

Effect of ceramic foam material and its microstructure parameters on combustion characteristics of porous media

Based on the Kelvin model, the mathematical relation between microstructure parameters of ceramic foam (including strut length, strut radius and cubic node length) and its macroscopic characteristics, i.e. thermal conductivity and porosity, has been established. The effects of the ceramic type and its microstructure parameters on the methane/air premixed combustion behaviors in a two-layer porous burner were studied numerically by software FLUENT. The results indicate that when the gas flow rate is 60 cm/s and the stoichiometric ratio of methane/air mixture is 0.6, SiC foam burner exhibits the highest gas and solid phase temperatures, and the stable operating range decreases in the sequence of SiC, ZrO₂ and Al₂O₃. Besides, the increase of microstructure dimensionless parameter d (the ratio of cubic node length to strut length) will result in the reduction of gas and solid temperatures and also the change of flame anchoring location, whereas the variation of e (the ratio of strut radius to strut length) has slight effect on the temperature distributions of gas and solid phases. Hence, the microstructure parameters, i.e. cubic length and struct length, should be considered in priority for the actual selection of porous burner material.