微圆管壁面材料和厚度对甲烷催化着火的影响

The Effects of Wall Materials and Thickness on Methane Catalytic Ignition in Micro-Tubes

对负载Pt催化剂的微圆管内CH_4的催化着火进行了非稳态和稳态模拟,重点研究了壁面材料和厚度对CH_4催化着火所需预热温度(表征着火温度)、着火时间、系统稳定时间以及极限着火条件的影响。非稳态研究结果表明:CH_4催化着火所需的预热温度与壁面条件无关,但着火时间和系统达到稳定状态所需的时间受壁面条件的影响较大,壁面热容量(mc)越大,着火及系统稳定时间越长;当壁面导热系数较小时,CH_4的催化着火发生在微圆管出口处,反应峰值区域随时间逐渐向进口移动,当壁面导热系数较大时,着火发生在进口处,且峰值反应位置不变。稳态结果显示,壁面轴向上热量的回流(大的导热系数和适当的壁面厚度)可以有效地拓宽甲烷的极限着火范围。

The transient and steady simulations of CH4 catalytic ignition in Pt-coated micro-tubes were conducted to investigation the effects of wall materials and thickness on the preheating temperature for ignition(representing ignition temperature),times for ignition and steady-state and critical ignition conditions.The results of transient simulations show that the catalytic ignition temperature of CH4 has no matter with wall conditions,but ignition and steady-state times are significantly affected.The micro-tubes with bigger thermal capacity need longer time to get ignited and steady.With non-conductive walls,catalytic ignition occurs at the exit of the micro-tube,and the peak reaction area moves upstream with time;while with conductive ones,catalytic ignition occurs at the entrance,and the position of peak reaction area keeps unmoved.The steady simulation results show that heat recirculation along the solid wall(good thermal conductivity and proper wall thickness)could broaden the range of critical ignition conditions.