Hydrotreated vegetable oil as enabler for high-efficient and ultra-low emission vehicles in the view of 2030 targets

Studies consider the influence of biofuels on the decarbonization of the transport system not negligible. The employment of fossil fuels with an even higher degree of renewable biofuel content, produced with a mature technology process, such as the Hydrotreated Vegetable Oils (HVO), are expected to increase. The research community expects valuable research results to exploit the HVO characteristics in ultra-low emission vehicles equipped with internal combustion engines. In this context, new findings in setting combustion control parameters through proper experimental design are carried out on a modern internal combustion engine architecture. An advanced injection system capable of precise close-coupled multiple injections per cycle was utilized. Steady-state engine operating conditions were selected for this experimental study. Combustion, efficiency, and engine-out emissions indicators with HVO fuel are compared with standard diesel. For assessing the difference in combustion stages, a second derivative method data analysis was performed. It is found that in comparison to diesel fuel, HVO significantly reduces regulated engine-out emissions at the same efficiency and EU 6c NOx emissions targets. To this aim, a specific set of engine control parameters were adopted. The PM decreased up to 10 %, corresponding to 0.18 g/kWh, while the CO2 reduced by about 7-8% in the range of 0.2-0.5 g/kWh. The decrease of the total PN ranges between 10 and 55%, depending on the control strategy and test point, and the particle distribution shifts towards smaller particle sizes. Outstanding improvements of the NOx-soot trade-off are verified, which in turn demonstrates the capability to operate the engine at post-EU6 NOx conditions without performance and comfort penalties. Engine-out CO and HC emission reductions are confirmed.