Assessment of optimized calibrations in minimizing GHG emissions from a Dual Fuel NG/Diesel automotive engine

•NG substitution ratios higher than ~40/65% not feasible at low/medium loads.•Combustion phasing results the most influential parameter in Dual Fuel engine control.•Optimized calibration provides a CO2 saving during WLTC of ~12% wrt standard Diesel.•Optimized calibration provides a THC reduction during WLTC of ~50% wrt a non-optimized DF map. Natural gas is recognized as a valid alternative to conventional fuels for internal combustion engines, thanks to its characteristics of low environmental impact and considerable natural reserves. In a Dual Fuel (DF) NG/Diesel configuration, NG offers interesting possibilities in terms of nitrogen oxides and soot emissions abatement, with reduced CO2 levels. Despite a proven feasibility of the DF concept for heavy duty engines, its applicability to light duty engines still clashes with several issues, especially the high unburned hydrocarbons emission. The present activity was devoted to assess the potentiality of an optimized DF engine calibration, to minimize GHGs emissions. A first experimental campaign on an automotive Diesel engine, equipped with an advanced combustion control, illustrated the effects of crucial control parameters on DF combustion. Hence, an optimization procedure permitted to identify the optimal set of control parameters. Finally, experiments in steady state and transient conditions allowed quantifying the THC and CO2 emissions reductions achievable moving from a starting DF engine map to the optimized calibration. The investigations highlighted that an adequate engine recalibration can offer a CO2 saving of about 12%, compared to the standard Diesel configuration, whereas the detrimental effect in terms of THC emissions could not be fully eliminated. Nevertheless, compared to a non-recalibrated DF map, the engine parameters optimization allowed achieving a THCs reduction of roughly 50%. Reported results could provide valuable information on behavior tendencies of a DF engine, useful for the development of dedicated engine technologies for DF combustion systems.