Resumen de Analysis of the combustion process and soot formation in a single cylinder optical engine fueled with e-fuels and using different piston geometries
The emissions reduction in internal combustion engines (ICE) is one of the greatest technical challenges of society. Although new technologies for mobility are emerging, the ICE will still have a key role in transport over the next decades. Diesel engines are challenging in terms of pollutant emissions, in particular nitrogen oxides (NOX) and particles. In fact, the last one represents 50 % of total emissions of this kind of engine. In this context, new hardware technologies as well as new renewable fuels have shown great potential to reduce soot emissions without affecting engine efficiency (CO2) emissions. For this reason, the impacts of using e-fuels (OMEX and FT-diesel) and different piston bowl geometries (re-entrant, stepped lip and stepped lip-wave bowl) on soot formation and combustion development were analyzed in a single cylinder optical diesel engine. First, an in-cylinder flow characterization when using a real bowl shape was performed by applying particle image velocimetry (PIV) technique. Subsequently, the flame movement, combustion process and soot formation were analyzed for different piston geometries through several optical techniques such as combustion image velocimetry (CIV), natural luminosity, OH* chemiluminescence and 2 color pyrometry. Finally, the combustion process and soot formation when using different e-fuels were studied by applying the same optical techniques used previously. In addition, for this part of the study, it was included a specific optical technique named high-speed spectroscopy for the soot analysis. Regarding the bowl geometries evaluation, the stepped lip and wave-stepped lip presented a faster late soot oxidation in comparison with the re-entrant geometry. Under extreme soot conditions, differences were also observed between the wave-stepped lip and the stepped lip. A faster soot oxidation was observed for the first one. The e-fuels showed a remarkable reduction in soot formation (especially OMEX) when compared with fossil diesel. From the spectroscopy analysis, it is possible to state the absence of soot during the combustion of pure OMEX. In general, the application of new hardware (bowl geometries) as well as new kind of fuels in diesel engines have presented a great potential in order to diminish the soot emissions.
