排气温度影响柴油机SCR尿素沉积物生成模拟研究

Simulation Study on the Influence of Exhaust Temperature on the Formation of SCR Urea Sediment in Diesel Engine

构建一个包含15种组分和11步反应的详细尿素分解化学反应动力学模型,对比了详细反应和总包反应的NH3生成量,计算结果吻合,认为新构建的详细机理模型能够预测尿素真实的分解过程。分析尿素在内燃机中150℃~400℃不同排气温度下的分解过程,探究这些温度下沉积物的生成和分解,结果表明,排气温度的高低对沉积物的生成和分解起重要作用,低温时沉积物生成明显,异氰酸是尿素分解副产物形成所需的最重要的反应物,缩二脲是尿素沉积物形成中最重要的中间产物。

A detailed urea decomposition chemical reaction kinetics model consisting of 15 components and 11 reactions was constructed to compare the NH3 production of the detailed reaction and the total package reaction. The calculated results are consistent. It is believed that the newly constructed detailed mechanism model can predict the true urea decomposition process. The decomposition process of urea in the internal combustion engine at different exhaust temperatures from 150 ℃ to 400 ℃ was analyzed to explore the formation and decomposition of sediments at these temperatures. The results show that the temperature of the exhaust gas plays an important role in the generation and decomposition of sediments. At the time of sedimentation,isocyanate is the most important reactant required for the formation of urea decomposition byproducts. Biuret is the most important intermediate in the formation of urea deposits.