In order to provide guideline for choosing a suitable tube-wall thickness (δ) for the micro-jet methane diffusion flame, the effect of tube-wall thickness on the blow-off limit is investigated via numerical simulation in the present work. The results show that the blow-off limit of micro-jet methane diffusion flame firstly increases and then decreases with the increase of tube-wall thickness. Subsequently, the underlying mechanisms responsible for the above non-monotonic blow-off limit are discussed in terms of the flow filed, strain effect and conjugate heat exchange. The analysis indicates that the flow field is insignificant for the non-monotonic blow-off limit. A smaller strain effect can induce the increase of the blow-off limit from δ=0.1 to 0.2 mm, and a worse heat recirculation effect can induce the decrease of the blow-off limit from δ=0.2 to 0.4 mm. The non-monotonic blow-off limit is mainly determined by the heat loss of flame to the tube-wall and the performance of tube-wall on preheating unburned fuel. The smallest heat loss of flame to the tube-wall and the best performance of tube-wall on preheating unburned fuel result in the largest blow-off limit at δ=0.2 mm. Therefore, a moderate tube-wall thickness is more suitable to manufacture the micro-jet burner.

为了为微喷甲烷扩散火焰选择合适的管壁厚度（δ）提供指导，在本工作中通过数值模拟研究了管壁厚度对吹扫极限的影响。结果表明，随着管壁厚度的增加，微喷甲烷扩散火焰的喷出极限先增大后减小。随后，从流场，应变效应和共轭热交换的角度讨论了导致上述非单调排放极限的潜在机理。分析表明，对于非单调排放极限，流场无关紧要。较小的应变效应会导致吹出极限从δ增大= 0.1到0.2 mm，更差的热再循环效果会导致吹出极限从δ = 0.2降低到0.4 mm。非单调排放极限主要由火焰对管壁的热损失和管壁在预热未燃烧燃料时的性能决定。火焰对管壁的最小热损失以及在预热未燃烧燃料时管壁的最佳性能导致最大的吹扫极限为δ = 0.2 mm。因此，适当的管壁厚度更适合于制造微射流燃烧器。