Emission reduction in a light-duty compression ignition engine using Hydrotreated Vegetable Oils (HVO) through recalibration of exhaust gas recirculation rate and main injection timing

Hydrotreated Vegetable Oil (HVO) is an alternative paraffinic fuel that differs in properties from EN590 diesel providing a drop-in, low-carbon diesel substitute that can be used with little to no engine modification, helping compression ignition engines to meet stricter emissions regulations while maintaining performance and reliability. However, engine re-calibration tailored for HVO can further improve PM-NO x trade-off of a diesel engine. Currently, Exhaust Gas Recirculation (EGR) is used to reduce NO x emissions, and combining it with HVO is expected to yield further emission reductions. The first part of this study examines the impact of uncooled EGR on engine combustion and emissions when operating with HVO. Additionally, Main Injection Timing (MIT) is another key engine parameter influencing emissions. Thus, the second part of this work explores the combined effects of uncooled EGR and ±2°CA adjustments in MIT for further emissions improvements with HVO. A parametric study was conducted on HVO combustion, focusing on thermodynamic parameters and engine-out emissions. At the Original Equipment Manufacturer MIT with 0% EGR, HVO usage led to up to a 40% reduction in PM and HC without significant changes in engine-out NO x . Introducing a low level of EGR with HVO reduced NO x emissions by up to 15%, while PM levels remained stable. The use of HVO, therefore, enables achieving lower NO x and PM emissions compared to the D2 fuel by slightly increasing the EGR rates and/or slightly retarded timing of the main injection, while also lowering HC emissions. The use of HVO, due to its high cetane number and absence of aromatics and sulfur, hence, enables reducing GHG emissions and also toxic regulated emissions compared to the use of EN590 diesel fuel.