As the late combustion phase in SI engines is of high importance for a further reduction of fuel consumption and especially emissions, the impacts of unburnt mass, located in a small volume with a relatively large surface near the wall and in the top land volume, is of high relevance throughout the range of operation.
To investigate and quantify the respective interactions, a state of the art Mercedes-Benz single cylinder research SI-engine was equipped with extensive measurement technology. To detect the axial and radial temperature distribution, several surface thermocouples were applied in two layers around the top land volume. As an additional reference, multiple surface thermocouples in the cylinder head complement the highly dynamic temperature measurements in the boundary zones of the combustion chamber. Furthermore, the cylinder is equipped with four pressure transducers and four distance sensors to determine the pressure distribution in the top land and the current piston position respectively.
Based on a wide range of operating points, this work shows differences in the temperature distribution of the top land volume as well as the flame propagation into different boundary zones of the combustion chamber towards the late combustion phase. Furthermore, the temperature measurements are used to quantify the heat transfer characteristics of the late combustion phase in homogeneous and stratified DI-SI operation mode.