Investigation on the effect of engine control parameters to optimize a light duty engine in Dual Fuel NG/Diesel configuration

The interest in natural gas (NG) as a candidate for a more sustainable fuel market finds certainly reasons in NG low carbon content and relatively high natural reserves. The concept of Dual Fuel (DF) Diesel-NG engines is not new, but its applicability to light duty automotive engines still clashes with several issues, as the high unburned hydrocarbon emission, mainly at low/partial engine loads. An extensive experimental campaign on a 2.0L automotive Diesel engine, equipped with an advanced combustion control, provided a thorough characterization of the engine behavior in DF mode. This research activity was devoted to assess the potentiality of a proper DF engine recalibration in the reduction of greenhouse gases emissions. The effects of crucial engine control parameters (like NG substitution ratio, Diesel injection timing and quantities, EGR) on DF combustion were evaluated and discussed.Hence, an optimization procedure was applied to the collected experimental data in order to identify an optimal set of control parameters. Then, a final experimental validation in transient driving cycles allowed quantifying the capability of the obtained calibration to reduce THC and CO2 emissions. The investigation highlighted the important role of combustion phasing and EGR in DF engine control and that an adequate recalibration can produce CO2 saving of about 12% with respect to the standard Diesel configuration and a THC reduction of roughly 50% compared to a non-recalibrated DF map.