碳基材料氧化烧蚀的双平台理论和反应控制机理

A dual platform theory for carbon-based material oxidation with reaction-diffusion rate controlled kinetics

针对高超声速飞行器所到达的表面温度和压力范围,就碳基材料在氧化速率控制区、过渡区、扩散控制区的烧蚀特性开展了深入研究。发现CO2在烧蚀过程中扮演重要角色,是不能忽略的。无因次质量烧蚀率随温度变化的曲线应该存在两个平台,且都属于扩散控制区,而不是此前普遍认为的只有一个平台。从理论上阐明了双平台产生的机理,发现第一平台是由于生成CO2将氧消耗完产生的,另一个平台是生成CO引起的。文献中所谓的"快反应"和"慢反应"之说反映问题是不全面的,它们只是我们给出的新模型的两种极端情况,用一个统一的模型就可以将它们连接起来,而且随着温度的升高,会从所谓的"快反应"经过第一平台自动过渡到"慢反应"。双平台理论澄清了此前的一些争议,并且得到了试验证实,为准确预估烧蚀量奠定了基础。

The combustion of carbon-based materials in a high speed stream of dissociated air is analyzed, together with the oxidation mechanism from reaction rate controlled regime through the transition to diffu-sion controlled oxidation.The product of the heterogeneous reaction of carbon with oxygen is known to be CO and CO2 ,and CO2 is generally usually neglected when surface temperature is higher than 1000K in many literatures.However,we find that CO2 plays an important role in the whole oxidation processes,and can’t be ignored through the three regimes.It is shown that two different platforms existed in the diffusion con-trolled regime.The first platform results from a reaction of the predominant CO2 product,and the other is due to the predominant CO product reaction.In fact,the concepts of “fast”reaction and “slow”reaction are not proper,since the two are the extreme cases of the general model we proposed.As surface temperature ri-ses,the oxidation process will change automatically from nominated “fast”reaction to “slow”reaction.The dual platform theory has been confirmed by several experimental results.