Diesel Oxidation Catalyst and HC Investigations of a Low RON Gasoline Fuel in a Compression Ignition Engine 2017-01-2405
Fuels from crude oil are the main energy vector used in the worldwide transport sector. But conventional fuel and engine technologies are often criticized, especially Diesel engines with the recent “Diesel gate”. Engine and fuel co-research is one of the main leverage to reduce both CO2 footprint and criteria pollutants in the transport sector. Compression ignition engines with gasoline-like fuels are a promising way for both NOx and particulate emissions abatement while keeping lower tailpipe CO2 emissions from both combustion process, physical and chemical properties of the low RON gasoline.
To introduce a new fuel/engine technology, investigation of pollutants and After-Treatment Systems (ATS) is mandatory. Previous work  already studied soot behavior to define the rules for the design of the Diesel Particulate Filter (DPF) when used with a low RON gasoline in a compression ignition engine. The aim of this study is to investigate the impact of such fuel/engine technology on the Diesel Oxidation Catalyst (DOC) for low load operating conditions. Hydrocarbon (HC) speciation is performed upstream (Us) and downstream (Ds) of the DOC. Warm-up and efficiency are also tested for different operating conditions. To finish, exothermal capacities are considered to ensure high temperature levels for DPF regeneration.
Upstream and downstream DOC HC speciation showed heavier molecules for Diesel fuel compared to low RON gasoline and higher carbon balance. These results are consistent with fuel composition. Upstream DOC main HC family is olefin for Diesel while it appears to be paraffin from low RON gasoline. Regardless of the fuel, upstream DOC HC species are mainly C1 to C4 and methane is the major downstream molecule.
For steady hot conditions, conversion efficiency of HC and CO for both fuels are quite similar. Differences are highlighted for transient conditions from cold to warm. For low load operating conditions, due to high amounts of HC and CO for low RON gasoline combustion, the catalyst seems to be poisoned and light-off temperatures are higher than Diesel ones. Moreover, the HC storage, during the light-off, is lower when using low RON gasoline.
Finally, DOC exotherm for regeneration is possible with low RON gasoline post-injections. For a same fuel quantity injection regardless of the fuel, low RON gasoline has higher upstream DOC HC amount and generates higher exotherms.
Despite some differences in the HC species between Diesel and low RON gasoline, conversion efficiency and DOC exotherm are quite similar. Nevertheless, the light-off and the HC-storage during a warm-up phase could be different and need more investigations.
Citation: Chaillou, C., Bouet, A., Frobert, A., and Duffour, F., "Diesel Oxidation Catalyst and HC Investigations of a Low RON Gasoline Fuel in a Compression Ignition Engine," SAE Technical Paper 2017-01-2405, 2017, https://doi.org/10.4271/2017-01-2405. Download Citation