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

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.

Automated summary

Nowadays, internal combustion engines are required to reduce pollutant emissions to comply with strict regulations in the transport sector. This paper examines the impact of using two different radial-lip based designs on soot formation and combustion behavior in a compression ignition engine. The results show that a more pronounced radial-lip geometry can drive the flames closer to the bowl center, reducing in-cylinder soot formation. The improvement is particularly noticeable under high EGR conditions, suggesting a potential to reduce the trade-off between soot and NOX emissions in compression ignition engines.