Potential of Modern Diesel Engines with Lowest Raw Emissions - a Key Factor for Future CO ₂ Reduction 2009-26-0025

The high-speed Dl-diesel engine has made a significant advance since the beginning of the 90's in the Western European passenger car market. Apart from the traditional advantage in fuel economy, further factors contributing to this success have been significantly improved performance and power density, as well as the permanent progress made in acoustics and comfort. In addition to the efforts to improve efficiency of automotive powertrains, the requirement for cleaner air increases through the continuous worldwide restriction of emissions by legislative regulations for diesel engines. Against the backdrop of global climate change, significant reduction of CO₂ is observed. Hence, for the future, engine and vehicle concepts are needed, that, while maintaining the well-established attractive market attributes, compare more favorably with regard to fuel consumption. A substantial step towards improvement of the mileage in passenger car diesel engines is analogous to the tendency on the gasoline counterparts, the reduction in cylinder displacement, in other words “downsizing”. Strategies for the realization of downsizing concepts and their effect on fuel consumption and emissions have already been discussed in numerous publications. The open questions, however, are the extent to which cylinder displacement should be lowered in the future and the resulting specific power achievable. In the scope of this paper, the potential for further increase in specific power of passenger car diesel engines is analyzed and discussed. Here, feasible measures are brought under consideration, in order to obtain maximum possible specific power, at lowest emissions and minimized fuel consumption. In this article, the downsizing degrees are shown as a function of specific power, along with the consequences they have on engine-out emissions and process efficiency. The displayed results are based on systematic theoretical treatment and detailed CFD simulations for air flow, charge motion and combustion. It represents in-cylinder investigation, as well as forecasting test cycle simulations for targeted vehicle applications.