Influence of an Adjustable Tumble-System on In-Cylinder Air Motion and Stratification in a Gasoline Direct Injection Engine

To meet future emission standards with gasoline direct injection engines it is important to have a reliable process robustness during stratified charge operation. Especially engines with a wide spacing arrangement of fuel injector and spark plug which operate with an air-guided concept are very sensitive concerning misfire operation caused by cyclic variations of the mixture formation and transport. Primarily the turbulent in-cylinder gas motion and the interaction with the fuel injection indicate these fluctuations. To reduce these cycle-to-cycle variations and to generate a steady flow behavior an adjustable air-guiding system was developed and attached to the inlet port of a single-cylinder DI engine. The following examinations show that the air-guiding system can lead to a significant reduction of the cycle-to-cycle-variation of the in-cylinder air flow. As a result of these improvements, the deviation of imep in the fired engine decreases obviously.