Development of After-Treatment Systems and Control Strategy for a Hybrid-Dedicated Homogeneous Lean Burn Engine

The development of lean-burn gasoline engines has continued due to their significant improvements in thermal efficiency. However, challenges associated with NOx emissions have hindered their mainstream adoption. As a result, the development of an effective NOx after-treatment system has become a key focus in lean-burn engine research. Additionally, HC emissions pose another challenge, as they tend to increase under lean combustion conditions while their conversion efficiency simultaneously declines. This study presents a novel after-treatment system incorporating a lean NOx trap(LNT) and a passive SCR(pSCR) system. This configuration enables efficient NOx reduction at a competitive cost while maintaining operational simplicity. Moreover, conventional catalyst technologies, including three-way catalysts (TWCs) and fuel-cut NOx traps (FCNTs), were optimized to maximize conversion performance under lean operating conditions. To further enhance system performance, various control strategies were explored, including advanced temperature management of after-treatment systems, the regeneration strategy of LNT, and optimized catalyst purge strategies during the cold-start phase. The proposed after-treatment system and control strategies were validated through vehicle testing on a chassis dynamometer. The results demonstrated that a hybrid vehicle equipped with a lean-burn gasoline engine and new after-treatment system can achieve a 10% improvement in fuel efficiency while remaining compliant with future emission regulations, underscoring its viability for real-world applications.