SULEV: Diesel-Exhaust Gas Aftertreatment heading to Super Ultra Low Emissions

摘要

The Corporate Average Fuel Economy (CAFE) regulation demands for a continuous fuel consumption reduction of light-duty vehicles in the US. As light-duty vehicles operated with diesel engines provide higher fuel efficiencies compared to gasoline vehicles and higher cruising ranges than electric vehicles, an increase of the diesel market share would help to meet the US market's requirements. However, the emission limits for nitrogen oxides and nonmethane organic gas (NO_x + NMOG) have to be concurrently reduced below levels, which can be achieved with today's production technologies for diesel emission concepts. In this study, an advanced exhaust gas aftertreatment concept is developed for a Jaguar XF E-segment vehicle with an I4 2.2l diesel engine to meet the emission standards for super ultra low emission vehicles, SULEV. The applied aftertreatment system has been selected by a validated system simulation of numerous architecture options and consists of a close-coupled electrically heated catalyst (EHC) followed by a near-coupled SCR on filter (SCR/DPF) and underbody SCR system. The dosing and mixing of AdBlue upstream of the SCR/DPF is optimised for a very compact package by a simulationsupported design process. A uniform reductant distribution at the SCR/DPF inlet was achieved by the development of an application-specific mixer and an advanced watercooled dosing system. It is shown, that the low exhaust gas temperature activity of the exhaust gas aftertreatment can be increased by applying advanced SCR catalyst technologies in combination with an improved warm-up strategy. A model-based calibration of the combustion process and the EHC operation results in an optimised tradeoff between warm-up behaviour and fuel economy. While the advanced exhaust gas aftertreatment architecture provides the potential to meet SULEV emission requirements on a concept level, the impact on controls and diagnostics, fuel efficiency and green house gas emissions is pointed out. It has to be noted, that the competitiveness of SULEV diesel production vehicle concepts strongly depends on their applicability with respect to system complexity and package requirements, robustness and durability, fuel quality and total costs of ownership.