Search Results

Future emission standards will require further reduction of harmful gaseous emissions such as HC, CO and NOx as well as consideration for greenhouse gas emissions such as CO₂. Gasoline engines with lean combustion spray-guided direct fuel injection in conjunction with turbocharging have a very high potential for fuel savings. The main challenge for stratified lean GDI aftertreatment systems is the development of a catalyst system to fulfill the emission legislation requirements under low exhaust temperature operating conditions with efficient use of precious metals. In addition to the very stringent emission legislation another challenge for the introduction of lean gasoline engines in North America is the higher sulfur content of the fuel compared to Europe. In this paper exhaust gas aftertreatment requirements for stratified gasoline direct injection engines will be discussed and the latest advances in catalyst and system development will be shown.

New fuel economy standards intensify the power train development for more fuel efficient vehicles worldwide. Different approaches are utilized to improve the fuel efficiency of gasoline engines. Of all concepts, including downsizing plus turbocharging, stratified operation of spray-guided gasoline direct injection (GDI) engines show the greatest fuel savings benefit. A significant challenge for stratified GDI aftertreatment systems is to develop both catalysts and systems that can reduce the high amount and cost of precious metals currently needed to meet performance standards under low exhaust temperature operating conditions. Furthermore, tighter emission standards will exceedingly require high conversion rates for HC, CO and NOx. In this paper the most recently developed catalyst and systems for lean GDI aftertreatment will be compared with serial production EURO 5 systems against future legislated targets.

The oil ash accumulation on modern three way catalyst (TWC) as well as its influence on catalyst deactivation is evaluated as a parameter of oil consumption, kind of oil additive compound and additive concentration. The oil ash accumulation is characterized by XRF and SEM/EDX in axial direction and into the washcoat depth of the catalyst. The deposition patterns of Ca, Mg, P and Zn are discussed. The catalytic activity of the vehicle and engine bench aged catalysts is measured by performing model gas tests and vehicle tests, respectively. The influence of oil ash accumulation on the lifetime emission behavior of the vehicle is discussed.

To meet future emission levels the industry is trying to reduce tailpipe emissions by both, engine measures and the development of novel aftertreatment concepts. The present study focuses on a joint development of aftertreatment concepts for gasoline engines that are optimized in terms of the exhaust system design, the catalyst technology and the system costs. The best performing system contains a close-coupled catalyst double brick arrangement using a new high thermal stable catalyst technology with low precious metal loading. This system also shows an increased tolerance against catalyst poisoning by engine oil.