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Extinction characteristics of catalyst-assisted combustion in a stagnation-point flow reactor

机译：驻点流反应器中催化剂辅助燃烧的消光特性

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As a fundamental study to understand physical and chemical characteristics in catalyst-assisted combustion, numerical simulations of a stagnation-point flow combustor with a catalytic surface are performed. The combustible mixture of methane and air is blown on top of a platinum surface, forming a classical stagnation-point flow configuration. This geometry not only represents an on-chip microcombustor considered in recent studies, but it also serves as a canonical problem of combined heterogeneous/homogeneous combustion subjected to flow straining, which is a key parameter that governs the quenching and flammability limit. One-dimensional similarity formulation is derived with full consideration of detailed surface and gas-phase chemical kinetic models. Parametric studies are conducted to investigate the effects of strain rate, equivalence ratio, heat loss on the combustion, and extinction modes. The steady results showed that catalysis can largely extend the extinction limit, while suppressing the gas-phase reaction at lower strain rates. It was also found that the extension of the catalytic reaction quenching limit is sensitive to the mixture composition, suggesting the dominance of chemical aspects in catalytic combustion. The temperature versus strain rate response curves exhibit multiple branches of stable solutions, implying a possibility of hysteresis behavior in a coupled homogeneous-heterogeneous reactor. Extensive parametric studies in terms of the mixture equivalence ratio and the conductive heat loss parameter have revealed three distinct steady response regimes: a surface-dominant monotonic response, continuous two-branch response, and separated response showing an isolated surface-reaction island. The results are expected to provide insight into improving the overall combustion stability and efficiency of catalyst-assisted combustors.
机译：作为了解催化剂辅助燃烧中的物理和化学特性的基础研究，对具有催化表面的滞流燃烧器进行了数值模拟。甲烷和空气的可燃混合物吹到铂表面的顶部，形成经典的停滞点流动形态。这种几何形状不仅代表了最近研究中考虑的片上微型燃烧器，而且还充当了异质/均质燃烧相结合的典型问题，这是控制淬火和可燃性极限的关键参数。一维相似公式是在充分考虑详细的表面和气相化学动力学模型的基础上得出的。进行了参数研究，以研究应变率，当量比，热损失对燃烧和消光模式的影响。稳定的结果表明，催化可大大延长消光极限，同时在较低的应变速率下抑制气相反应。还发现催化反应淬灭极限的扩展对混合物组成敏感，表明催化燃烧中化学方面的优势。温度对应变率的响应曲线显示出稳定溶液的多个分支，这意味着在均相-非均相反应器中存在滞后行为的可能性。关于混合物当量比和传导热损失参数的广泛参数研究显示了三种不同的稳态响应机制：表面主导的单调响应，连续的两分支响应和分离的响应，它们显示了一个孤立的表面反应岛。预期结果将提供深入了解，以改善整体燃烧稳定性和催化剂辅助燃烧器的效率。

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