Holistic Development of Future Low NO _x Emission Concepts for Heavy-Duty Applications

Further tightening of NO_x emission standards as well as CO₂ emission limits for commercial vehicles are currently under discussion. In the on-road market, lowering NO_x emissions up to 90%, down to 0.02 g/bhp-hr, has been proposed by CARB and is evaluated by US EPA. Testing for in-service conformity using a portable emission measurement system (PEMS) is currently under review in the US. In Europe, CO₂ emission limits are anticipated and a CO₂ monitoring program is ongoing. PEMS legislation has been recently tightened and further restrictions can be expected. Stage V legislation has been introduced in Europe and it is foreseeable that further tightening of off-road standards will take place in the future. This study deals with virtual development and evaluation of future engine and exhaust aftertreatment (EAT) technology solutions to fulfill the diverse future emission requirements with emphasis on off-road applications. Considering a future emission standard scenario, first the NO_x reduction efficiency of different exhaust aftertreatment layouts is analyzed. Multiple EAT concepts and possible technology solutions combining different technologies are considered. It has been recognized that the future solutions require an integrated approach, combining both novel aftertreatment technology and engine related emission reduction measures. Using a phenomenological combustion model and predictive emission models, the engine model is virtually developed. The full-size physical engine model is coupled to the EAT model to enable a holistic system development. Technology packages for emission reduction and requirements to thermal management of the exhaust gas are defined accordingly. Evaluation of future EAT concepts, multiple emission reduction and advanced heating strategies are performed for a heavy-duty off-road application. Standard certification and a typical real cycle are considered and evaluated.