Emissions Optimization Potential of a Diesel Engine Running on HVO: A Combined Experimental and Simulation Investigation

The present work investigates a number of recalibration possibilities of a common rail turbocharged diesel engine, aiming at the improvement of its emissions performance and fuel consumption (FC), with Hydrotreated Vegetable Oil (HVO). Initially, steady-state experimental data with nominal engine settings revealed HVO benefits as a drop-in fuel. Under these conditions, pure HVO results in lower engine-out PM emissions, lower CO₂ emissions, and lower mass-based FC, while the respective NO_x emissions present a mixed trend. In mid loads and speeds NO_x emissions of HVO are lower while at higher loads and speeds are slightly higher compared to conventional diesel. At a second step, a combustion model was developed, in order to investigate the possible re-adjustments of IT (Injection Timing) and EGR (Exhaust Gas Recirculation) settings in order to exploit HVO’s properties for further reduction of emissions and FC. The results of the combustion model in steady-state conditions showed clear reductions in NO_x (up to 50%), PM (up 70%) to and CO₂ (up to 7%) emissions with HVO, when IT and EGR are recalibrated compared to market diesel at default engine settings. The investigation was extended with a vehicle simulation model, aiming to examine the performance of the recalibrated engine over the WLTP and the NEDC, focusing on CO₂ emissions and FC. New FC tables were built as output of the combustion model for the re-adjusted IT and EGR and were implemented in the vehicle model. According to the results, the improved IT and EGR settings for HVO, lead to lower CO₂ emissions (4% in WLTP and 2.5% in NEDC) and FC (3.9% in WLTP and 2% in NEDC) compared to diesel at nominal engine settings.