In the Selective Catalytic Reduction (SCR) system of a diesel engine, the decomposition of urea will produce the reducing agent NH₃, and by-products which will form deposits. To reduce deposits, this work studied the relationship between liquid film temperature and reactants. Further, the mixers with different structures and the injectors with different injection parameters were designed and compared with different designs about the location and mass of deposits. The evaporation and pyrolysis process of urea aqueous solution in an SCR system were simulated by using computational fluid dynamics (CFD) coupled with a detailed urea decomposition mechanism. The results indicated that the by-products (biuret, CYA, and ammelide) would be produced at 300, 380, and 437 K, respectively. With increasing liquid film temperature, the mass fraction of NCO⁻ and by-products also increased. The turbulence intensity varied when they were generated by the different mixer structures. In lower turbulence intensity of mixer1, with the decrease of injection angle and pressure, the mass and distribution regions of liquid film and deposits were obviously reduced. In higher turbulence intensity of mixer2, the urea droplets were entrained by strong turbulence. The decrease of the injection angle and pressure did not significantly reduce the liquid film and deposits.

在柴油发动机的选择性催化还原（SCR）系统中，尿素的分解将产生还原剂NH ₃以及会形成沉积物的副产品。为了减少沉积物，这项工作研究了液膜温度和反应物之间的关系。此外，设计了具有不同结构的混合器和具有不同喷射参数的喷射器，并就沉积物的位置和质量与不同设计进行了比较。利用计算流体力学（CFD）结合详细的尿素分解机理，对SCR系统中尿素水溶液的蒸发和热解过程进行了模拟。结果表明，副产物（缩二脲，CYA和酰胺）将分别在300、380和437 K下产生。随着液体薄膜温度，NCO的质量分数^-副产品也增加了。当湍流强度由不同的混合器结构产生时，湍流强度会发生变化。在较低的湍流强度下，随着注入角和压力的减小，液膜和沉积物的质量和分布区域明显减小。在混合器2的湍流强度较高的情况下，尿素液滴被强湍流夹带。注射角度和压力的减小并未显着减少液膜和沉积物。