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选择性催化还原(SCR)系统已被证明是大型柴油机控制氮氧化物(NOx)排放的有效方案。未来的大型柴油机被设计为有更高的NOx排放量,以提高燃油经济性,这需要越来越高的NOx转化效率以满足排放法规要求。为此,未来的后处理设计可采用先进的技术,如选择性催化转化(SCR)涂覆颗粒滤清器(SCRF)和涂覆在高孔隙度直通式载体上的SCR,以获得高转化效率。评价了不同的高NOx转化效率系统。首先,通过使用SCRF单元和附加的涂覆在高孔隙度载体的SCR涂层,设计了高性能的NOx控制催化剂。第二,评价了不同的控制策略,以了解还原剂剂量策略和热管理对NOx转化效率的影响。在1台大型柴油机上进行瞬态循环试验。提高氨投入量而不是尿素可进一步提高转化效率,尤其是在低温下无法喷入尿素的时候。此外,实施热管理改善了低温时的NOx转化效率。结果证明,这种系统加上发动机控制策略的改进可以使瞬态FTP测试循环中的NOx转化效率达到95%以上,从而可使柴油机满足未来排放法规和燃油经济性的目标。
Selective catalytic reduction (SCR) systems have proven to be effective solutions for large-scale diesel engine control of nitrogen oxide (NOx) emissions. Future large diesel engines are designed to have higher NOx emissions to improve fuel economy, which requires higher and higher NOx conversion efficiencies to meet emission regulations. For this reason, future reprocessing designs can employ advanced technologies such as SCR (Selective Catalytic Conversion) and SCR coated on highly porous straight-through supports to achieve high conversions effectiveness. Different high NOx conversion efficiency systems were evaluated. First, a high performance NOx control catalyst was designed by using an SCRF unit and an additional SCR coating on a highly porous support. Second, different control strategies were evaluated to understand the effect of reductant dosing strategies and thermal management on NOx conversion efficiency. In a large diesel engine for transient test cycle. Increasing the ammonia input rather than urea can further improve the conversion efficiency, especially at low temperatures when urea can not be injected. In addition, implementing thermal management improves NOx conversion efficiency at low temperatures. The results demonstrate that improvements in this system, coupled with engine control strategies, can achieve over 95% NOx conversion efficiency in transient FTP test cycles, enabling diesels to meet future emissions regulations and fuel economy goals.