Effects of titanium dioxide nanoparticles on hydrogen-enriched castor biodiesel blends for a diesel engine under dual-fuel operation
摘要
The present experimental investigation evaluates the combustion, performance, and emission characteristics of hydrogen-enriched castor biodiesel blends dispersed with titanium dioxide (TiO₂) nanoparticles in a single-cylinder, four-stroke, direct injection compression ignition (CI) engine operating under dual-fuel mode. Castor biodiesel blends containing 10% and 20% biodiesel by volume were tested with hydrogen induction rates of 5 and 10 LPM and TiO2 nanoparticle concentrations of 50 and 100 ppm under varying brake mean effective pressure (BMEP) conditions. The results demonstrated that hydrogen induction and TiO₂ nanoaddition significantly improved combustion and thermal performance. The BD10H10T100 blend exhibited the highest brake thermal efficiency of 30.76% at full load compared to 29.35% for diesel, while brake specific energy consumption decreased from 11.12 MJ kWh−1 to 10.49 MJ kWh−1. Hydrogen enrichment accelerated flame propagation and reduced ignition delay by nearly 3°CA, whereas TiO2 nanoparticles enhanced oxidation reactions and combustion completeness through catalytic activity and oxygen buffering behavior. In addition, peak exhaust gas temperature increased from 404 °C for diesel to 446 °C for BD10H10T100, indicating intensified combustion characteristics. Significant reductions in exhaust emissions were also observed for hydrogen-enriched TiO₂-assisted blends. At full load, CO emissions decreased from 49.72 g kWh−1 for diesel to 24.96 g kWh−1 for BD10H10T100, while HC emissions reduced from 0.323 g kWh−1 to 0.2565 g kWh−1. Similarly, smoke emissions decreased from 7.11 g kWh−1 for diesel to 6.37 g kWh−1. However, NOx emissions increased from 13.0 g kWh−1 for diesel to 14.35 g kWh−1 because hydrogen enrichment increased peak in-cylinder temperature and thermal residence time, thereby promoting thermal NOx formation. Overall, the combined utilization of castor biodiesel, hydrogen enrichment, and TiO2 nanoparticles improved combustion efficiency and reduced incomplete combustion emissions, demonstrating strong potential for cleaner and more efficient dual-fuel CI engine operation.