The effective use of ethanol for greenhouse gas emissions reduction in a diesel engine 2019-36-0157
Regulations have been established for the monitoring and reporting of greenhouse gas (GHG) emissions and fuel consumption from the transport sector. Low carbon fuels combined with new powertrain technologies have the potential to provide significant reductions in GHG emissions while decreasing the dependence on fossil fuel. In this study, a lean-burn ethanol-diesel dual-fuel combustion strategy has been used as means to improve upon the efficiency and emissions of a conventional diesel engine. Experiments have been performed on a 2.0 dm3 single cylinder heavy-duty engine equipped with port fuel injection of ethanol and a high-pressure common rail diesel injection system. Exhaust emissions and fuel consumption have been measured at a constant engine speed of 1200 rpm and various steady-state loads between 0.3 and 2.4 MPa net indicated mean effective pressure (IMEP). Compared to a baseline diesel-only operation, the ethanol-diesel dual-fuel engine yielded up to 57% lower well-to-wheels GHG emissions. Moreover, the dual-fuel combustion strategy attained higher net indicated efficiency than the conventional diesel mode from 0.6 to 2.4 MPa IMEP, with a maximum value of 47.2% at 1.2 MPa IMEP. The analysis also revealed that the use of ethanol resulted in 26% to 90% lower nitrogen oxides (NOx) emissions than the conventional diesel operation. This was attributed to the formation of a more premixed and low temperature combustion process for a dual-fuel operation with an ethanol energy fraction that varied from 56% to 79%. Soot levels from the dual-fuel combustion were maintained comparatively low, with a filter smoke number of less than 0.235. Carbon monoxide and unburned hydrocarbon emissions, however, increased significantly in the dual-fuel combustion. This will likely require the application of a high efficiency oxidation catalyst. Overall, this experimental study demonstrated that a dual-fuel combustion with a low carbon fuel such as ethanol is an effective means of decreasing the dependence on diesel fuel and associated GHG emissions.