Non-Uniform Cylinder-to-Cylinder Combustion for Cost-Effective Lean NOx Trap Regeneration

Meeting the stringent EPA Tier 3 emission standards has been one of the main challenges towards the commercialization of highly-efficient lean-burn gasoline engines in the United States. One of the potential aftertreatment solutions is three-way catalyst (TWC) coupled with lean NO
_x
trap (LNT). LNT requires frequent regeneration via rich engine combustion, which can cause a fuel penalty by up to 3%. In this study, a non-uniform cylinder-to-cylinder combustion (NUCCC) strategy and a cost-effective TWC-LNT system with a new architecture, were proposed to reduce the fuel penalty associated with LNT regeneration. The air-to-fuel equivalence ratios for different cylinders were optimized using genetic algorithm. The proposed NUCCC strategy and new TWC-LNT system were verified over a simplified FTP-72 cycle in simulation. Simulation results demonstrated the NUCCC-based regeneration strategy could reduce the fuel penalty by 61.80%, compared to the traditional uniform cylinder-to-cylinder combustion (UCCC) based LNT regeneration strategy.