Search Results

To meet the future challenges of reducing fuel consumption and exhaust emissions, load and speed dependent control of mixture formation and the combustion process are necessary. Although variable intake systems will contribute to this issue, current designs are characterized by costly deactivation mechanisms and have sensitivity to production tolerances. In this paper, a new type of variable intake and mixture formation system is presented, which offers a new, economical and reliable way to control mixture formation and charge motion. A theoretical analysis was done to determine the best geometric dimensions and subsequent experimental results demonstrated the best potential strategies for reducing fuel consumption and exhaust emissions through improvements in lean burn capability and EGR-tolerance. Compared to conventional port deactivation systems, all control features have been realized with a reduced number of required parts.

The future challenges for spark ignition (SI) engines to drastically reduce the exhaust emissions and fuel consumption while still maintaining high specific power output will be addressed. In order to further improve stoichiometric engine concepts with three-way-catalyst, reduced cold start and warm-up fuel enrichment as well as a higher EGR tolerance gain fundamental importance. Both objectives will be met if the combustion system of the engine features a high lean burn capability. Due to less freedom of multi-valve engines in combustion chamber shapes, resulting in minor squish effects, the intake generated charge motion plays the dominant role to assure an efficient combustion of even highly diluted mixtures. Basing on results of experimental combustion and flow test bench studies, the performance of swirl and tumble intake systems for multi-valve SI engines will be compared and evaluated.

It can be expected that the high speed DIdiesel enginewill play a major role as a drive system for passenger cars and light duty vehicles. The reason is its fuel consumption which is the lowest of all combustion engines. Of course, low exhaust emission levels expecially particulates (PM) and nitric oxides NOx are a requirement in this context. Exhaust gas recirculation (EGR) can contribute decisively to achieve acceptable emission levels with high speed DI diesel engines. On the basis of fundamental investigations into the influence of EGR on the combustion process of DI diesel engines, it will be shown how the exhaust gas should be recirculated to obtain effective emission reductions. In particular, it was found that so called “Hot EGR” which keeps the temperature of the recirculated exhaust gases at a very high level, not only helps to reduce NOx but also contributes distinctly to achieve lower hydrocarbon (HC) and PM emissions.