Investigation of an Innovative Combustion Process for High-Performance Engines and Its Impact on Emissions

Over the past years, the question as to what may be the powertrain of the future has become ever more apparent. Aiming to improve upon a given technology, the internal combustion engine still offers a number of development paths in order to maintain its position in public and private mobility. In this study, an innovative combustion process is investigated with the goal to further approximate the ideal Otto cycle. Thus far, similar approaches such as Homogeneous Charge Compression Ignition (HCCI) shared the same objective yet were unable to be operated under high load conditions. Highly increased control efforts and excessive mechanical stress on the components are but a few examples of the drawbacks associated with HCCI. The approach employed in this work is the so-called Spark Assisted Compression Ignition (SACI) in combination with a pre-chamber spark plug, enabling short combustion durations even at high dilution levels. This operation mode leads to substantial improvements in terms of fuel consumption up to highest load conditions. Developed in close collaboration with Volkswagen Motorsport and the FKFS, the experimental investigations are carried out on a single cylinder test bench at the Technical University of Munich (TUM). The test bench is directly derived from the Volkswagen WRC 1.6l DI-SI race engine. In a numerical approach, the 3D-CFD engine development tool QuickSim is used to gain a detailed understanding of charge motion, mixture formation, and combustion. As a first step, we want to assess the effects of engine operating parameters such as engine load and engine speed on both boosted conventional and SACI operation. Secondly, we want to give an overview on the magnitude of the formulation of NO_x and particle emissions in the presence of different ignition modes. The latter is aimed at addressing one of the many remaining questions in order to apply SACI operation to series production engines.