Molecular simulations of surface ablation using reaction probabilities from molecular beam experiments and realistic microstructure
Molecular simulations of surface ablation using reaction probabilities from molecular beam experiments and realistic microstructure
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使用分子束实验的反应概率和真实的微观结构对表面烧蚀进行分子模拟
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
T. Minton
中科院分区：
文献类型：
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作者：
Savio J. Poovathingal;T. Schwartzentruber;Vanessa J. Murray;T. Minton
对高温离解氧与理想碳/碳复合材料的反应进行了分子模拟，解决了材料的微观结构问题。用直接模拟蒙特卡罗方法模拟了反应物向微观结构的对流和扩散以及表面反应产物向微观结构的迁移。进行了有无气相化学反应的模拟，以确定与材料表面附近的气相反应相比，气相表面反应的相对重要性。这些模拟包含了基于在分子束装置中获得的新的反应散射数据的单个气体-表面碰撞的反应概率。分子束实验清楚地表明，大多数表面反应产物是通过热机制产生的。这些实验提供了关于O、O2、CO和CO2从具有代表性的材料样品上散射的相对大小的详细数据，该样品由玻璃碳组成。对于800K的气体表面温度，模拟发现，尽管CO是表面反应的主要产物，但在微观结构区域内，气相交换反应生成了大量的CO2。微结构区域内的二氧化碳产生量取决于基于暴露的微结构高度的局部克努森数。最后，对一个真实的碳碳(C-C)表面进行了初步的模拟。表面拓扑是通过烧蚀的C-C样品的X射线显微层析成像获得的，该样品被三角化，并直接用于气体-表面相互作用的DSMC模拟。
Molecular simulations are performed of high temperature dissociated oxygen reacting with an idealized carbon-carbon composite material, where the microstructure is resolved. The Direct Simulation Monte Carlo (DSMC) method is used to simulate the convection and diffusion of reactants towards the microstructure and the transport of surface reaction products away from the microstructure. Simulations are performed with and without gas-phase chemical reactions in order to determine the relative importance of gas-surface reactions compared to gas-phase reactions next to the material surface. The simulations incorporate reaction probabilities for individual gas-surface collisions based on new reactive scattering data obtained in a molecular beam facility. The molecular beam experiments clearly indicate that a majority of surface reaction products were produced through thermal mechanisms. The experiments provide detailed data on the relative magnitude of O, O2, CO, and CO2 scattering from a representative material sample, made of vitreous carbon. For a gas-surface temperature of 800K, it is found from the simulations that despite CO being the dominant surface reaction product, a gas-phase exchange reaction forms significant CO2 within the microstructure region. The amount of CO2 production within the microstructure region is shown to be dependent on the local Knudsen number, based on the exposed microstructure height. Finally, preliminary simulations are performed for a real CarbonCarbon (C-C) surface. The surface topology is obtained through X-ray microtomography of an ablated C-C sample, which is triangulated and used directly within a DSMC simulation of the gas-surface interaction.