模型孔中化学气相渗透过程的热解碳沉积模拟

Modeling of Chemical Vapor Infiltration for Pyrocarbon within Capillaries

研究耦合均气相反应机理和总括反应机理,以模拟甲烷在模型孔中的热解碳沉积过程。在平推流反应器模型中,利用均气相反应机理对甲烷裂解的气相组分的变化进行模拟,并将平推流反应器相应位置的气体组分浓度作为模型孔入口初始浓度。运用包含总括反应机理及氢气抑制模型的热解碳沉积模型,对甲烷在模型孔中的化学气相渗透过程进行模拟。在温度1373和1398 K,甲烷压强10~20 k Pa,停留时间0.08和0.2 s下,沿模型孔深度方向的热解碳平均沉积速率的模拟结果与文献报道的实验结果有较好的吻合。模拟结果表明：热解碳平均沉积速率随甲烷压强和模型孔深度的增加而增大,且通孔的沉积速率要低于相应实验条件下一端闭孔的模型孔沉积速率。

Coupling homogeneous gas-phase reaction mechanism with lumped reaction mechanism, the pyrocarbon deposition process of the methane pyrolysis was simulated within the capillaries. The initial concentrations for the involved gas-phase species at the mouth of capillary are obtained firstly by computation of the plug flow using homogeneous gas-phase reaction mechanism during methane pyrolysis. Chemical vapor infiltration of pyrocarbon from methane in the capillary is simulated by deposition model, hydrogen inhibition model and lumped reaction mechanism. Predicted results for the mean deposition rate along the capillary depth are well validated by previously published experimental results, in which, at temperatures of 1373 and 1398 K, methane pressures are ranging from 10 to 20 k Pa, and residence times are of 0.08 and 0.2 s. Simulated results show that the gradient of the mean deposition rate profile increases with methane pressure and capillary depth, and the deposition rate for transition capillary is lower than the corresponding closed capillary.