Improvement of vehicle fuel economy, both over legislated drive cycles and in the real world, remains one of the critical challenges facing powertrain engineers. Market pressures and CO2 emissions targets dictate that innovative approaches to the efficiency of gasoline combustion engines must continue to be made. The Lean Boost downsized gasoline engine concept combines direct injection and lean operation at high load to allow high compression ratio to be maintained in a pressure charged engine. Investigation of this technology in a European C-class demonstration vehicle has shown the potential to compete with the diesel engine for drive cycle CO2 emissions at significantly lower manufacturing cost. The production feasibility of the Lean Boost concept is critically dependent on control of NOx emissions in an engine which operates lean at all engine operating conditions, including high load. For a new gasoline-fuelled concept there is a need to demonstrate the feasibility of achieving low tailpipe NOx emissions under all real world driving conditions, not just over legislated drive cycles. The NOx emission control issues are discussed with reference to experimental engine results and simulation studies. Both Lean NOx Trap (LNT) and ureabased Selective Catalytic Reduction (SCR) aftertreatment systems are considered in typical European and US specification vehicle applications. The Lean Boost downsized direct injection gasoline engine concept is a cost effective route to deliver 20% CO2 reduction. The production feasibility of the Lean Boost concept is dependent on control of NOx emissions in an engine which operates lean at all engine operating conditions, including high load. Either LNT or urea-based SCR solutions would provide sufficient NOx conversion in a Lean Boost application and operating cost would be similar for both systems. Based on current precious metal prices, the aftertreatment system costs for LNT will be significantly higher than for SCR. The cost of the urea dosing and storage equipment for SCR redresses some of the higher LNT catalyst costs, but at current precious metal prices, there a net 200-600 Dollar price difference for European and US applications.
NO(x) emission control options for the Lean Boost downsized gasoline engine
Möglichkeiten der NOx Emissionskontrolle beim verkleinerten Lean Boost-Verbrennungsmotor
2007
34 Seiten, Bilder, Tabellen, 4 Quellen
Conference paper
Storage medium
English
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