Additive manufacturing new piston design and injection strategies for highly efficient and ultra-low emissions combustion in view of 2030 targets

Internal combustion engines have been the most effective solution as the main mover for mobility. Despite the recent European regulations targeting zero tailpipe CO2 emissions for new passenger cars and light vans from 2035 onwards, the upcoming emission regulations still require further technology and fuel developments in the transport sectors. In recent years, studies on internal combustion engines have been increasingly shifting from performance and refinement through advanced fuel injection and air charging technologies to ultra-low emissions and efficiency. Particular attention has also been paid to carbon–neutral fuels. The problem merits further investigation since all are key factors for the powertrain competitiveness in the electrified automotive future, as the pollutants and the CO2 emissions will soon approach the Euro 7 regulation and the Fit to 55 standards, respectively. To this aim, the combustion system design is a crucial part of the internal combustion engine development in the view of exploiting renewable fuel characteristics. This study seeks to assess the effectiveness of a steel piston, realized through a specific design for additive manufacturing technologies, enabling an innovative bowl geometry. It features a highly re-entrant sharp-step and radial lips bowl profile enabling spray separation and radial mixing zone concept. A single-cylinder compression ignition engine has been employed to demonstrate the effectiveness of the innovative bowl shape to meet the challenging future ultra-low emission targets. The results confirm the additive manufacturing technology as a possible solution for innovative highly-stressed steel piston designs. The new bowl shape design, combined with optimised spray targeting and injection strategies, allows outstanding soot reductions, up to 80%, and ultra-low NOx emission levels compared to the conventional combustion system. Gains in fuel economy are also observed. Further emissions advantages are expected with renewable fuel applications.