Combustion and emission characteristics of hydrotreated pyrolysis oil on a heavy-duty engine

•Ignition delay increases as blend ratio increases in combustion research unit.•Engine can be operated without change with 30% hydrotreated pyrolysis oil blends.•Hydrotreated pyrolysis oil blends show identical engine combustion process as diesel.•Hydrotreated pyrolysis oil responds well to various injection timing and pressure.•Hydrotreated pyrolysis oil blends yield higher soot emissions than diesel. Second-generation biofuel is promising to be applied in the field of long-haul transportation, aviation, and marine shipping. This work focuses on the ignition behavior, combustion process, and emission characteristics of hydrotreated pyrolysis oil. This biomass-derived oil was blended with marine gas oil from 10 to 30 wt% without a co-solvent or emulsifier. Tests were performed both on a combustion research unit and a commercial heavy-duty diesel engine setup. The results from the combustion research unit reveal that ignition delay increase as hydrotreated pyrolysis oil blend ratio increases at tested ambient conditions. Engine tests were first performed under factory settings at representative load/speed points based on the European stationary test cycle for benchmarking. Then start of injection and fuel pressure are varied to check the controllability and engine sensitivity of hydrotreated pyrolysis oil blends. It is shown that under engine conditions, the combustion characteristics and heat release are quite identical among hydrotreated pyrolysis oil blends and diesel. Though all cases present ultra-low particulate matter emissions, hydrotreated pyrolysis oil blends yield higher particulate matter emissions, which increase as the blend ratio increases. The particulate matter/NOx tradeoff is observed both for benchmarking tests and parameter study. The results indicate that the engine can run with HPO blends smoothly and safely without major modification.