Sustainable diesel engine performance using hydrous hydrazine emulsions: Hydrogen carrier potential and NOx emission reduction with aluminum oxide catalyst

• Hydrous hydrazine acts as a hydrogen carrier and NOx suppressant in diesel fuel. • Al₂O₃ nanoparticles enhance fuel performance and reduce harmful emissions. • Nanoparticle characterization confirms catalytic activity and thermal stability. • CDF30HHN improves BSFC by 15.2% and BTE by 11.3% over non-catalyst fuels. • CDF30HHN reduces smoke by 16.4%, HC by 19.3%, and CO by 10.7% compared to CDF30HH. The growing demand for cleaner and more sustainable diesel engine technologies has directed focus to alternative fuel methods. This study examines the application of hydrous hydrazine (HH) as a dual-function fuel additive, acting as both a hydrogen carrier and NOx suppressant, to improve diesel engine performance and emissions. Emulsion fuels, including 15% and 30% HH in conventional diesel fuel (CDF), were developed utilizing Sorbitan monooleate as a surfactant. To enhance hydrazine breakdown, aluminum oxide (Al 2 O 3 ) nanoparticles, analyzed using SEM, XRD, and FTIR, were utilized as catalysts owing to their porous architecture, thermal resilience, and crystalline characteristics. Experimental assessments were conducted on a single-cylinder diesel engine. The results indicated that the addition of HH reduced in-cylinder pressure by 4.7% and net heat release by 14.3%. While 30% HH blends elevated BSFC (45.4%), HC (23.9%), and CO (19.3%) emissions, they concurrently resulted in significant decreases in brake thermal efficiency (15.6%) and NOx emissions (12.4%) relative to CDF. The incorporation of the Al 2 O 3 catalyst resulted in reductions of 15.2% in BSFC, 19.3% in HC, and 10.7% in CO emissions, while BTE increased by 11.3%. CDF30HHN accomplished a 16.4% decrease in smoke opacity relative to its non-catalytic equivalent. Although there was a slight increase in NOx with the inclusion of the catalyst, total NOx emissions were still lower than those from CDF. This work highlights the feasibility of HH emulsions with Al₂O₃ catalysis as a sustainable and efficient approach to enhance diesel engine performance while reducing environmental impact.