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The TSI engines from Volkswagen demonstrate the potential offered by gasoline direct injection in combination with charging. In general, great importance is attached to the development of new gasoline engine combustion methods for reducing fuel consumption and hazardous emissions. In the near future, the combination of gasoline direct injection and engine charging will make up the greatest share of new car registrations in the European region.
Behind this technological trend is an effort to replace large-displacement naturally-aspirated engines by smaller, economical engines that are charged without compromising torque or power. The reduced engine displacement enabled by charged engines achieves reductions in friction losses and weight. In addition, operating points in the customer-relevant range of driving profiles are shifted to more efficient engine operating regions. The Volkswagen corporation has assumed a leadership role in this direction with its TFSI and TSI concepts.
The focus of current combustion process developments is on the jet-guided combustion method and combining it with charging. In contrast to prior air-guided or wall-guided combustion methods, characterized by lateral orientation of the injector and a defined generated charge movement, in the jet-guided combustion method the mixture is formed solely by the spray characteristics of the injector arranged centrally at top of the combustion chamber. This enables lean operation that is exceptionally stable and exhibits charge stratification over a broad engine map region.
Fulfillment of current and future emission laws represents a continuing challenge. In particular, the high NOx emissions generated in lean operation require expensive exhaust treatment. External exhaust gas recirculation is used in the jet-guided combustion method to suppress these emissions upstream in the engine. Introducing external exhaust into the combustion chamber reduces combustion temperature, thereby inhibiting the generation of nitrogen oxides.
Jet-guided gasoline direct injection in combination with charging opens up a broad playing field for reducing CO2 emissions. In customer-relevant operating ranges, reductions in fuel consumption of up to 20 percent are possible compared to engines in production today.
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