Improved Engine Efficiency and Clean Combustion of Non-Edible Biodiesel/Alcohol Blends and Hydrogen Enrichment Strategy

This study evaluates the performance, combustion, and emission characteristics of a Kirloskar TV1 compression ignition engine fueled with an 80% Hevea brasiliensis biodiesel and 20% n-Octanol blend (HB80OCT20) under hydrogen induction rates of 8, 10, 12, and 14 LPM. Hydrogen enrichment significantly influenced combustion phasing and energy utilization. The maximum brake thermal efficiency (BTE) of 32.33% was achieved at 14 LPM under full-load conditions, accompanied by the lowest brake specific energy consumption (9.752 MJ/kWh), indicating enhanced premixed combustion and rapid energy release. However, this condition also produced the highest peak cylinder pressure (88.72 bar), elevated heat release rate, increased NOâ‚“ formation, and noticeable engine vibration, suggesting operation near the upper combustion intensity threshold. Hydrocarbon (HC), carbon monoxide (CO), and smoke emissions were substantially reduced with hydrogen induction, with minimum HC, CO, and 39% smoke reduction observed at 8 LPM compared to diesel. Conversely, NOâ‚“ emissions increased with hydrogen flow rate due to intensified thermal loading associated with faster combustion kinetics. A multi-criteria composite score analysis incorporating efficiency, emissions, and combustion stability parameters identified 10 LPM (13.12% hydrogen energy share) as the optimal operating condition. At this rate, BTE improved by 4.4% over diesel while maintaining controlled NOâ‚“ levels and stable peak pressure (82.4 bar), providing the best overall performance–emission balance. The findings demonstrate that moderate hydrogen induction (10–12 LPM) optimizes flame propagation and carbon oxidation without inducing excessive combustion intensity, making it a technically viable and sustainable strategy for renewable dual-fuel diesel engine applications.