Numerical Assessment of an Innovative Piston Bowl Concept in a Light-duty Diesel Engine

A numerical assessment of an innovative bowl geometry, featuring both a stepped-lip and radial-bumps, was carried out in order to evaluate its impact in terms of soot and NOx emissions as well as of fuel consumption. As a test case, a 4-cylinder 1.6L diesel engine for passenger car applications was selected. Starting from a validated 3D-CFD engine model, including a calibrated spray model and a detailed chemistry combustion model, a spray targeting study was initially carried out in order to optimize the spray pattern for the innovative bowl design. Next, in order to investigate the effects of the innovative bowl geometry on in-cylinder mixing and combustion processes, a sensitivity analysis on injection timing, injection pressure and EGR (Exhaust Gas Recirculation) rate was carried out. Results confirmed a significant impact of the innovative bowl shape on the combustion process and showed that the new bowl design can lead to significant reductions of soot emissions and fuel consumption compared to conventional bowl geometries, with a significant improvement of both soot-NOx and BSFC-NOx trade-offs.