Successive diesel engine emissions’ regulations impose increasingly tighter limits on the automotive industry. A well-established method to meet nitrogen oxides emissions’ requirements is selective catalytic reduction with a urea-water solution injection. State-of-the-art designs are based on close-coupled exhaust architecture which suffers from a lack of space for a proper decomposition of a urea-water solution. The optimization of such systems is very challenging and is always intensively supported by numerical simulations. Within this work a two-zone spray representation for a urea-water solution injection is proposed. The two-zone approach captures a non-uniform droplet distribution inside the spray cone while maintaining a reasonable calculation time, since it is still based on a Lagrangian method. The proposed model was applied into exhaust system simulations and tested against a standard spray representation. The results revealed that uniform spray representation led to a smaller wall film formation and different mass balance. Ammonia distribution at the catalyst inlet was not directly affected significantly; however, in real systems one could expect catalyst clogging due to wall film formation, followed by a decrease of ammonia distribution uniformity. The results clearly show that uniform spray representation may lead to misestimation of the selective catalytic reduction system’s performance and the novel two-zone approach should be used instead.

连续不断的柴油机排放法规对汽车行业施加了越来越严格的限制。满足氮氧化物排放要求的公认方法是通过注入尿素水溶液选择性催化还原。最先进的设计基于紧密耦合的排气结构，该结构缺少尿素水溶液能适当分解的空间。这种系统的优化非常具有挑战性，并且始终受到数值模拟的大力支持。在这项工作中，提出了用于尿素水溶液注射的两区域喷雾表示法。由于它仍然基于拉格朗日方法，因此两区方法可在保持合理的计算时间的同时捕获雾锥内部的不均匀液滴分布。所提出的模型已应用于排气系统仿真中，并针对标准喷雾表示法进行了测试。结果表明，均匀的喷雾表示导致较小的壁膜形成和不同的质量平衡。催化剂进口处的氨分布没有直接受到明显影响。但是，在实际系统中，人们可能会期望由于壁膜的形成而导致催化剂堵塞，进而降低氨分布均匀性。结果清楚地表明，均匀喷雾表示可能会导致对选择性催化还原系统性能的错误估计，应改用新颖的两区方法。催化剂进口处的氨分布没有直接受到明显影响。但是，在实际系统中，人们可能会期望由于壁膜的形成而导致催化剂堵塞，进而降低氨分布均匀性。结果清楚地表明，均匀喷雾表示可能会导致对选择性催化还原系统性能的错误估计，应改用新颖的两区方法。催化剂进口处的氨分布没有直接受到明显影响。但是，在实际系统中，人们可能会期望由于壁膜的形成而导致催化剂堵塞，进而降低氨分布均匀性。结果清楚地表明，均匀喷雾表示可能会导致对选择性催化还原系统性能的错误估计，应改用新颖的两区方法。