Enhancing efficiency and emission characteristics of a dual-fuel engine using spirulina biodiesel–ethanol blends with nanoparticles and hydrogen infusion

The present study aims to investigate the effect of ethanol and Titanium Dioxide (TiO₂) nanoparticles (NPs) as additives in Spirulina platensis oil methyl ester (SPOME)-diesel blends as pilot fuel, along with Hydrogen (H₂) as a secondary fuel, to determine the performance, combustion, and emission characteristics of a dual-fuel Compression Ignition (CI) diesel engine. Biodiesel was synthesized from Spirulina platensis oil via transesterification at a 1:6 oil-to-methanol molar ratio, yielding 97.2%. A B20 blend (20% SPOME + 80% diesel) was initially prepared, followed by B20E20 (20% vol. of Ethanol + B20). Further, TiO₂ NPs (50 mg/L) were dispersed in the B20E20 sample. These additive-enhanced blends were tested in a dual-fuel CI engine, with and without H₂ induction, at varying loads. The stability and homogeneity of the NP-dispersed blends were confirmed through FESEM, HRTEM, FTIR, SAED, and XRD analyses. Performance parameters such as Brake Thermal Efficiency (BTE) increased by 10.4%, and Brake Specific Fuel Consumption (BSFC) decreased by 13.3% significantly for the B20E20 + TiO₂50 + 6H₂ blend at higher load. Emissions of CO, CO₂, and HC reduced by 36.3%, 6.68%, and 8.36%, respectively. Although NOx emissions slightly increased with H₂ induction, the B20E20 blend exhibited reduced NOx at higher load. Combustion characteristics, including Cylinder Pressure (CP) and Heat Release Rate (HRR), were enhanced by 11.53% and 7.91%, respectively, for the H₂-infused B20-alcohol-NP blend. Overall, the B20E20 + TiO₂50 + 6H₂ fuel formulation demonstrates strong potential as a sustainable alternative to conventional diesel in dual-fuel CI diesel engines.