Reduced models for the evaporation and decomposition of urea-water solution in exhaust gas systems are developed to improve computational efficiency for detailed simulations. The models describe a droplet or wall film of urea water solution in hot exhaust gas, which is simulated in detail including gas phase chemistry and an evaporation model for the urea decomposition. The time scales of all involved processes are analyzed and it is found that only during the phase of urea decomposition transport and chemistry are coupled, while there is no significant chemistry during the preceding phase of water evaporation and no significant transport after complete evaporation and decomposition. Based on these results reduced models for all phases are suggested and a two-dimensional tabulated model for the processes in the gas phase and the urea decomposition phase is developed, which accurately reproduces the results of detailed simulations.

开发了废气系统中尿素水溶液蒸发和分解的简化模型，以提高详细模拟的计算效率。这些模型描述了热废气中尿素水溶液的液滴或壁膜，对其进行了详细的模拟，包括气相化学和尿素分解的蒸发模型。对所有涉及过程的时间尺度进行分析，发现只有在尿素分解阶段，运输和化学是耦合的，而在水分蒸发的前一阶段没有显着的化学，在完全蒸发和分解后没有明显的运输。