Comparison of soot issued from diesel and naphtha combustion

Christophe  Chaillou, Aramco Fuel Research Center

In a global effort to reduce the CO2 footprint of oil-based transportation fuel, Aramco and IFP Energies nouvelles are developing an innovative fuel/engine design. The objective is to use, in a compression ignition engine, a less-processed fuel, commonly denominated as naphtha. Benefits from both lower CO2 footprint from well-to-tank, and lower CO2 as well as pollutant emissions from tank-to-wheel are expected. Today, when introducing innovative fuel formulations or new engine technologies, the investigation of after-treatment systems (ATS) requirements related to current and future pollutant regulation is mandatory.

In this context, the present work focuses on investigating structure and properties of the particulate matter produced using naphtha fuel in a compression ignition engine and comparing them to diesel particulates. In addition, the impact of a fuel borne catalyst (FBC) is also studied. Characterization of soot is performed through the backpressure of the diesel particulate filter (DPF), soot oxidation velocities with engine test bench measurements and thermogravimetric analysis (TGA). Composition and structure analysis are assessed with transmission electron microscopy (TEM).

Despite the very different composition of both fuels, observed differences between naphtha and conventional diesel soot are very low or null for all the parameters investigated in the scope of the present work. FBC introduction has the same impact on soot oxidation for both fuels. A slightly lower oxidation velocity of naphtha soot has been observed, most likely linked to oxygenated species present in diesel fuel.

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