【摘要】 微燃烧器中的火焰由于外壁面的散热损失较大而容易失去稳定性,通过上游壁面的热循环则能使火焰稳定性得到增强。这两方面都依赖于燃烧器的壁面传热过程,它和壁面厚度及导热系数密切相关。本文选择两个壁面厚度(δ=0.2和0.4 mm)和两种壁面材料(石英和碳化硅),通过数值模拟研究了这两个参数对平板型微燃烧器中氢气/空气火焰稳定性的影响。结果显示:当壁厚δ=0.2 mm时,两种材料的微燃烧器内火焰都发生了倾斜现象,但是碳化硅燃烧器出现得更晚。当壁厚为δ=0.4 mm时,石英燃烧器在更大速度时(相对于δ=0.2 mm)仍然发生了火焰倾斜现象,但是碳化硅燃烧器中不再出现。分析表明:壁厚增大能够强化热循环,同时减少散热损失;此外,相对于石英燃烧器来说,碳化硅燃烧器的热循环比例更大,散失损失比例更小。总之,当微燃烧器的壁厚和导热系数较大时,它能获得更大的稳燃极限。更多还原

【Abstract】 Flame is prone to lose its stability in micro-combustors due to the large amount of heat loss from the external walls.On the other hand,heat recirculation through the upstream combustor walls can enhance flame stability.These two aspects depend on the structural heat transfer,which is associated with the thickness and thermal conductivity of the combustor walls.In the present study,the effects of wall thickness and material on flame stability were numerically investigated by selecting two thicknesses(δ=0.2 and 0.4 mm)and two materials(quartz and SiC).The results show that when δ=0.2 mm,flame inclination occurs at a certain inlet velocity in both combustors,but it happens later in SiC combustor.For δ=0.4 mm,flame inclination still occurs in quartz combustor from a larger inlet velocity compared to the case of δ=0.2 mm.However,flame inclination in SiC combustor with δ=0.4 mm does not happen and it has a much larger blowout limit.Analysis reveals that a thicker wall can enhance heat recirculation and reduce heat loss simultaneously.Moreover,SiC combustor has larger heat recirculation ratio and smaller heat loss ratio.In summary,the micro-combustor with thicker and more conductive walls can harvest large flame stability limit.更多还原