Evaluation of H-atom adsorption on wall surfaces with a plasma molecular beam scattering technique
Evaluation of H-atom adsorption on wall surfaces with a plasma molecular beam scattering technique
复制标题
DOI：
10.1016/j.proci.2018.08.061
复制
发表时间：
2019
影响因子：
3.4
通讯作者：
Y. Saiki;I. Kinefuchi;Yong Fan;Yuji Suzuki
中科院分区：
文献类型：
--
作者：
Y. Saiki;I. Kinefuchi;Yong Fan;Yuji Suzuki
为了精确模拟火焰-壁面相互作用中的壁面化学效应，采用一种新发展的分子束散射技术，利用非平衡等离子体驱动束源和超高真空室，直接研究了不同壁面上的自由基吸附。首先，每个自由基物种的吸附速率的壁面化学效应的敏感性进行了研究，通过一系列的数值模拟与详细的气体/表面化学甲烷-空气预混火焰。由于H原子具有较高的扩散性，并且其吸附显著地抑制了H + O2= O + OH的链支化反应，因此与OH、O和CH 3相比，H被认为是对火焰特性（例如热释放速率或CO排放）影响最大的自由基。在灵敏度分析的基础上，利用等离子体分子束散射测量技术对石英和SUS 321表面的H吸附进行了定量分析。证实了通过等离子体解离H2分子可以成功地产生H原子束。然后，将产生的H束照射到不同壁温Tw的石英和SUS 321表面。结果表明，H在石英和SUS 321表面上都有吸附，在Tw = 673 K时，HPH的反应几率都有最大值。这可能是因为复合速率随Tw的增大而增大，而脱附速率也随之增大，并在Tw> 673 K时克服了复合速率。对SUS 321发动机的PH值与我们以前的燃烧实验结果相一致，用本方法可以得到更精确的PH值。
Toward a precise modeling for wall chemical effects in flame-wall interactions, radical adsorption on different wall surfaces are directly evaluated through a newly-developed molecular beam scattering technique using a non-equilibrium plasma–driven beam source as well as an ultra-high vacuum chamber. Firstly, sensitivities of adsorption rates for each radical species to the wall chemical effect are examined through a series of numerical simulations with detailed gas/surface chemistry for a methane-air premixed flame. Since H-atom has a higher diffusivity and its adsorption significantly inhibits a chain branching reaction of H + O2= O + OH, H is considered to be the most influential radical on the flame characteristics such as heat release rate or CO emission if compared to OH, O and CH3. Based on the sensitivity analysis, H adsorptions are quantified for quartz and SUS321 surfaces with the plasma molecular beam scattering measurements. It is confirmed that H atomic beam can be successfully produced through the plasma dissociation of H2molecules. Then, the produced H beam is irradiated onto quartz and SUS321 surfaces at different wall temperaturesTw. It is found that H is adsorbed on the quartz and SUS321 surfaces, and reaction probabilities of HPHhas its maxima atTw∼673 K for both surfaces. This is probably because that the recombination rate increases asTwincreases, while the desorption rate is also promoted and overcomes the recombination rate atTw> 673 K. ThePHfor the SUS321 is in agreement with that in our previous combustion experiments and more precise value can be obtained by the present method.