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首页> 外文期刊>Journal of Heat Transfer >A Mathematical Model for Heat and Mass Transfer in Methane-Air Boundary Layers With Catalytic Surface Reactions
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A Mathematical Model for Heat and Mass Transfer in Methane-Air Boundary Layers With Catalytic Surface Reactions

机译：具有催化表面反应的甲烷-空气边界层传热和传质的数学模型

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Catalytic combustion of hydrocarbon mixtures involves the adsorption of the fuel and oxidant into a platinum surface, chemical reactions of the adsorbed species, and the desorption of the resulting products. Re-adsorption of some produced gases is also possible. The catalytic reactions can be beneficial in porous burners that use low equivalence ratios. In this case, the porous burner flame can be stabilized at low temperatures to prevent any substantial gas emissions, such as nitric oxide. The present paper is concerned with the numerical computation of heat transfer and chemical reactions in flowing methane-air mixtures over a platinum coated hot plate. Chemical reactions are included in the gas phase and in the solid platinum surface. In the gas phase, 16 species are involved in 49 elementary reactions. On the platinum hot surface, additional surface species are included that are involved in 24 additional surface chemical reactions. The platinum surface temperature is fixed, while the properties of the reacting flow are computed. The flow configuration investigated here is the parallel boundary layer reacting flow. Finite-volume equations are obtained by formal integration over control volumes surrounding each grid node. Up-wind differencing is used to ensure that the influence coefficients are always positive to reflect the physical effect of neighboring nodes on a typical central node. The finite-volume equations are solved iteratively for the reacting gas flow properties. On the platinum surface, surface species balance equations, under steady-state conditions, are solved numerically by an under-relaxed linear algorithm. A non-uniform computational grid is used, concentrating most of the nodes near the catalytic surface. Surface temperatures, 1150 K and 1300 K, caused fast reactions on the catalytic surface, with very slow chemical reactions in the flowing gas. These slow reactions produce mainly intermediate hydrocarbons and unstable species. The computational results for the chemical reaction boundary layer thickness and mass transfer at the gas-surface interface are correlated by non-dimensional relations, taking the Reynolds number as the independent variable. Chemical kinetic relations for the reaction rate are obtained which are dependent on reactants' concentrations and surface temperature.
机译：碳氢化合物混合物的催化燃烧涉及燃料和氧化剂在铂表面的吸附，吸附物质的化学反应以及所得产物的解吸。也可以重新吸附一些产生的气体。催化反应在使用低当量比的多孔燃烧器中可能是有益的。在这种情况下，多孔燃烧器的火焰可以在低温下稳定，以防止任何实质性的气体排放，例如一氧化氮。本文涉及在铂涂层热板上流动的甲烷-空气混合物中的传热和化学反应的数值计算。化学反应包括在气相和固体铂表面中。在气相中，有16种物质参与49个基本反应。在铂热表面上，还包括其他与24种其他表面化学反应有关的表面物质。铂表面温度是固定的，同时计算反应流的性质。此处研究的流态是平行边界层反应流。通过对每个网格节点周围的控制体积进行形式积分，可以得到有限体积方程。迎风差异用于确保影响系数始终为正，以反映典型中央节点上相邻节点的物理影响。对于反应气体的流动特性，迭代求解了有限体积方程。在铂表面上，通过欠松弛线性算法对稳态条件下的表面物种平衡方程进行数值求解。使用非均匀计算网格，将大多数节点集中在催化表面附近。表面温度1150 K和1300 K在催化表面上引起快速反应，在流动的气体中化学反应非常慢。这些缓慢的反应主要产生中间烃和不稳定物质。以雷诺数为自变量，通过无量纲关系对化学反应边界层厚度和气体-表面界面传质的计算结果进行了关联。获得了反应速率的化学动力学关系，其取决于反应物的浓度和表面温度。

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