Influence of Swirl and Tumble on Economy and Emissions of Multi Valve SI Engines

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. Special attention will be paid on the tumble formation process and measurement of the tumble intensities. A newly designed stationary tumble measurement method for development purposes will be demonstrated which enables to determine the tumble intensities.