Future emission regulations will further reduce the vehicle emissions of diesel engines significantly. In addition, increasing fuel prices due to increasing demands and limited crude oil resources place a strongly requires minimisation of fuel consumption. The competition between different propulsion units, modern gasoline engines, hybrid concepts and the HSDI Diesel engine, the classical aggregate with highest fuel efficiency, is developed for different market situations, with the most balanced cost of ownership for the final consumer. To meet the goal of achieving these strict limits while maintaining attractive market attributes in terms of driving pleasure and comfort, the combustion system must also be revised or redesigned in order to achieve the CO2 limits that will be enforced in the future, while at the same time clearly reducing untreated NO(x) emissions. In this article, the basic conditions for the optimal layout of a future, low NO(x)/low CO2 combustion system is discussed. The FEV combustion system HECS (High Efficiency Combustion System), a promising option, is defined and presented. Besides an enhanced power density of more than 80 kW/l, it achieves low fuel consumption values even in the high part load range, in conjunction with extremely reduced NO(x) emissions. The key elements for the achievement of the potential shown are: - Robust and homogeneous in-cylinder charge movement, - Efficiency-optimised gas exchange, - Adapted cylinder charge cooling (fresh air and EGR), - Improved fuel injection with excellent mixture formation and homogenisation, - Optimised combustion process with highest possible air utilization. The intelligent interlinking of these factors, on the basis of a comprehensive database and the assistance of the development process by modern software tools (CAE, DoE) for layout and testing, permits the favourable control of the small combustion chamber volumes, which stem from the trend towards engine capacity reduction ('Downsizing'). The complex technology package, with 2-stage turbocharging, intercooling and dual EGR path (HP as well as LP), also demands advanced control algorithms to manage the responsive cylinder charge composition of fresh air and EGR, switchable between two sources, and also the fast fuel injection actuation. The introduction of a novel model-based NO(x) control structure provides the base for such a fast and precise mixture control, even under transient conditions, as necessary for realisation of minimised engine-out NO(x) emissions at best possible CO2 values. The attached closed-loop combustion control serves, in addition, for smooth and comfortable engine operation, while both systems in combination also participate in active compensation of production related scattering in component performance. The presented concept offers the potential to meet future European emission standards with substantially reduced fuel consumption figures of appr. 5 ltr/100 km for medium-sized vehicle classes without active NO(x) aftertreatment.
Advanced clean-powerful hsdi diesel engine concept for lowest CO2 and emission requirements
2008
21 Seiten, 20 Bilder, 7 Quellen
Conference paper
Storage medium
English
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