A diesel oxidation catalyst (DOC) is widely used to oxidize partial combustion by-products, such as unburned hydrocarbons and carbon monoxide (CO), and nitric oxide (NO) from compression ignition (CI) engines. Numerical modelling of the DOC, reported in the literature, often does not predict the performance of the DOC accurately over a wide range of engine operating conditions because only a few chemical reactions are considered. The objective of this work is to develop a robust 1D transient numerical model, capable of accurately predicting the conversion efficiency of the engine-out total hydrocarbon (THC), CO and NO in a conventional diesel combustion mode. Based on experimental observations of the low temperature oxidation of CO and THC with nitrogen dioxide (NO2), the developed numerical model not only include oxidation reactions with oxygen but also the NO2 reduction and selective catalytic reduction (SCR) reactions to improve the robustness of the model. From the non-dimensional analysis, the kinetics and mass transfer limitation of exhaust gas species oxidation and their dependence on exhaust gas properties and DOC geometric parameters are identified. Relative magnitudes of resistances to chemical reaction and mass transfer reveal that CO oxidation in the DOC transitions from kinetically controlled to a mass transfer-controlled regime at the CO oxidation light-off temperature (218°C DOC inlet temperature), whereas, THC oxidation is in the kinetic controlled regime even at 377°C exhaust gas temperature. NO2 reduction in the DOC is always in the kinetic controlled regime; however, NO oxidation reaction transitions from kinetic to a mass transfer-controlled regime at 215°C.

中文翻译：

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以 NO2 还原为重点的柴油氧化催化剂的数值建模和无量纲分析

柴油氧化催化剂 (DOC) 广泛用于氧化部分燃烧副产物，例如压缩点火 (CI) 发动机中未燃烧的碳氢化合物和一氧化碳 (CO) 以及一氧化氮 (NO)。文献中报道的 DOC 数值模型通常无法准确预测 DOC 在各种发动机运行条件下的性能，因为只考虑了少数化学反应。这项工作的目标是开发一个强大的一维瞬态数值模型，能够准确预测传统柴油燃烧模式下发动机排出的总碳氢化合物 (THC)、CO 和 NO 的转化效率。基于二氧化氮（NO）低温氧化CO和THC的实验观察2），开发的数值模型不仅包括与氧气的氧化反应，还包括 NO2还原和选择性催化还原（SCR）反应，以提高模型的稳健性。通过无量纲分析，确定了废气物质氧化的动力学和传质限制及其对废气性质和 DOC 几何参数的依赖性。化学反应和传质阻力的相对大小表明，在 CO 氧化起燃温度（218°C DOC 入口温度）下，DOC 中的 CO 氧化从动力学控制转变为传质控制状态，而 THC 氧化则为即使在 377°C 的废气温度下，仍处于动力学控制状态。不2DOC 的减少始终处于动力学控制范围内；然而，NO 氧化反应在 215°C 时从动力学状态转变为传质控制状态。