Browse Publications Technical Papers 2020-37-0003
2020-06-23

Experimental Study of Additive-Manufacturing-Enabled Innovative Diesel Combustion Bowl Features for Achieving Ultra-low Emissions and High Efficiency 2020-37-0003

In recent years the research on Diesel thermodynamics has been increasingly shifting from performance and refinement to ultra-low emissions and efficiency. In fact, the last two attributes are key for the powertrain competitiveness in the automotive electrified future, especially in European market where 95gCO2/km fleet average and Euro6d RDE Step2 are phasing in at the same time. The present paper describes some of the most innovative research that GM and Istituto Motori Napoli are performing in the field, exploring how the steel additive manufacturing can be used to create innovative combustion bowl features that optimize the combustion process to a level that was not compatible with standard manufacturing technologies. In particular, an innovative highly-reentrant sharp-stepped profile featuring radial-lips has been studied on a 0.5l single-cylinder engine, coupled to a state of art 2500bar fast-acting fuel injection system, with the objective to demonstrate the full potential of optimized fuel stratification and spray separation enabled by the radial mixing zone concept. The results confirm that excellent reduction of engine-out emissions vs a Euro6-b design could be achieved with no detriment to the indicated efficiency nor engine power density, especially when compact injection patterns are applied at part load. In addition, sensitivity studies have been conducted to understand the optimal injection protrusion and spray indexing to the ribs, and to explore future improvements that will be tested in the second step of the project. A final comment is related to the additive manufacturing technology itself, as the prototype steel piston did not highlight any durability concerns even after extensive full load testing.

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