Exploring dual-fuel operation in direct injection diesel engines: an experimental study with blends of acacia biodiesel and hydrogen

Rising interest in low-carbon compression-ignition fuel strategies has motivated the co-induction of hydrogen with biodiesel blends. This study experimentally investigates a single-cylinder, four-stroke, direct-injection diesel engine fueled with Acacia biodiesel–diesel blend (ABD20) and hydrogen induction at 5 and 10 L/min. The corresponding hydrogen energy shares are 8.3% and 15.4%, designated as ABD5H2 and ABD10H2, respectively. The test fuels were compared with neat diesel and ABD20 over the investigated brake mean effective pressure range. Hydrogen induction reduced hydrocarbon, carbon monoxide, and smoke emissions relative to ABD20. At higher loads, ABD10H2 reduced smoke opacity by up to 20.45%, decreased brake-specific fuel consumption by up to 30%, and increased brake thermal efficiency by up to 1.0% relative to ABD20. Peak heat release rate and peak in-cylinder pressure increased by 3.46% and 4.76%, respectively. Hydrogen addition also increased NOx emissions, primarily because of the higher combustion temperature and faster heat release. Overall, ABD10H2 provided improved fuel economy and reduced smoke emissions compared with ABD20, demonstrating the potential of hydrogen enrichment for low-carbon diesel-engine operation.