Potential of using OMEx as substitute of diesel in the dual-fuel combustion mode to reduce the global CO2 emissions

Abstract

To achieve the targets of extreme low emissions values for the transport sector, several technologies emerged in the last few years. In this sense, advanced combustion modes as the dual-fuel low temperature combustion showed great advantages in terms of NOx and soot emissions reduction. At low and medium engine load, the operation is stable with virtually zero emissions. However, the exhaust gas recirculation rates at high load need to be increased to avoid excessive in-cylinder peaks, which leads to higher soot emissions. At these conditions, the use of non-sooting fuels as the oxymethylene dimethyl ethers (OMEx) allows avoiding the NOx-soot trade-off. In addition, the e-fuel consideration of the OMEx makes it suitable to reduce the global GHG emissions. This paper assesses the potential of using OMEx as high reactivity fuel to reduce the CO2 well-to-wheel emissions, and NOx and soot tailpipe emissions, in a medium-duty truck operating under dual-fuel combustion in transient conditions. The cargo mass was varied between 0% and 100% (18 ton) in the World Harmonized Vehicle Cycle. The tank-to-wheel analysis shows slightly higher CO2 production with OMEx-gasoline than with diesel-gasoline due to the ratio between the lower heating value and the carbon content. However, the well-to-wheel analysis shows the benefits of using OMEx to reduce the carbon dioxide footprint, which ranges from 13% (at full cargo mass) to 19% (at low cargo mass) compared to diesel-gasoline dual-fuel mode. This benefit is due to the large gains in terms of fuel production due to the carbon capture and the clean electric energy source necessary to produce the OMEx.