Influence of the radial-lip concept design to achieve ultra-low soot emission reductions: An optical analysis

Abstract

[EN] Nowadays, internal combustion engines must reduce pollutant emissions to achieve the upcoming strict regu-lations in the transport sector. In this context, new hardware designs have shown great potential to reduce pollutant emissions and comply with current and future regulations. This paper focuses on innovative bowl designs with radial lip protrusions, which are radially distributed inside the bowl. The potential of using these protrusions in order to reduce soot formation and improve soot oxidation has been demonstrated by different studies. For this reason, the present work addresses the impact of using two different radial-lip based geometries on soot formation and combustion behaviour in an optical single-cylinder compression ignition engine. High-speed OH* chemiluminescence imaging and 2-Colour pyrometry were applied simultaneously, in combination with a thermodynamic analysis of the in-cylinder pressure signal. The results show that more pronounced radial-lip geometry drive the flames closer to the bowl centre, where more oxygen is available to oxidize the soot, resulting in in-cylinder soot formation reduction. In addition, it has been observed that the improvement ach-ieved by the more pronounced radial-lip geometry is more noticeable under high EGR conditions. This opens a path to reduce the soot-NOX trade-off in compression ignition engines.