An optical investigation of Fischer-Tropsch diesel and Oxymethylene dimethyl ether impact on combustion process for CI engines

[EN] Synthetic fuels (E-fuels) have shown to be an interesting alternative to replace the fossil diesel fuel due to its CO2 reduction potential as well as for their capability to diminish the soot production and therefore for improving the soot-NOX trade-off in Compression Ignition engines. Thus, the main objective of this paper was to better understand the combustion process and the in-cylinder soot formation of two of the most popular E-fuels currently: Fischer-Tropsch (FT) diesel and Oxymethylene dimethyl ether (OMEX). To achieve this aim, a single cylinder optical CI engine with a commercial piston geometry was used. Thee optical techniques (Natural Luminosity-NL, OH* chemiluminescence and 2-color pyrometry) were applied to analyze the combustion evolution and quantify the soot formation at different loads (1.5, 4.5 and 7.5 bar IMEP). OMEX presented the largest injection duration due to the low LHV. For the NL analysis, OMEX showed the lowest light intensity for the three loads tested, indicating a very low soot production. Despite of the low NL intensity, it presented the highest OH* chemiluminescence signal, indicating a higher presence of near-stoichiometric zones due to the high amount of oxygen. Regarding FT diesel, it showed a combustion behavior similar to the commercial diesel. NL, OH* and 2-color technique analysis indicated that for the three conditions tested, FT diesel presented lower soot production and a faster soot oxidation than commercial diesel. This work was partially funded by Generalitat Valenciana through the Programa Santiago Grisolia (GRISOLIAP/2018/142) program. Pastor, JV.; García Martínez, A.; Mico Reche, C.; De Vargas Lewiski, F. (2020). An optical investigation of Fischer-Tropsch diesel and Oxymethylene dimethyl ether impact on combustion process for CI engines. Applied Energy. 260:1-12. https://doi.org/10.1016/j.apenergy.2019.114238 Benajes, J., García, A., Monsalve-Serrano, J., & Lago Sari, R. (2018). Fuel consumption and engine-out emissions estimations of a light-duty engine running in dual-mode RCCI/CDC with different fuels and driving cycles. Energy, 157, 19-30. doi:10.1016/j.energy.2018.05.144 Dronniou, N., Kashdan, J., Lecointe, B., Sauve, K., & Soleri, D. (2014). Optical Investigation of Dual-fuel CNG/Diesel Combustion Strategies to Reduce CO2 Emissions. SAE International Journal of Engines, 7(2), 873-887. doi:10.4271/2014-01-1313 Tanov, S., Wang, Z., Wang, H., Richter, M., & Johansson, B. (2015). Effects of Inject