Balancing Efficiency and Emissions: A Study on Biodiesel-Hydrogen Dual-Fuel Engine Performance Under Varying Injection Timings

The growing demand for cleaner energy sources has intensified research on alternative fuels for diesel engines to mitigate environmental concerns. This study presents a novel approach by investigating the combined effect of injection timing (IT) and hydrogen enrichment on the performance, combustion, and emissions of a single-cylinder, four-stroke variable compression ratio (VCR) engine fueled with a CI20 biodiesel-hydrogen dual-fuel blend. Injection timings of IT24, IT27, IT30, and IT33 degrees before TDC and hydrogen flow rates of 4, 8, 12, and 16 LPM were tested. The research showed that IT30 operating with 16 LPM hydrogen flow produced the maximum brake thermal efficiency (BTE) of 32.7% and the minimum brake-specific fuel consumption (BSFC) of 0.26 kJ/kWh while working at full load. The experimental conditions led to 7.7% higher cylinder pressure and an 8% enhancement of the heat release rate when compared with basic operation. The emission analysis showed that carbon monoxide (CO) decreased by 48%, hydrocarbons (HC) decreased by 22.2%, and the smoke opacity diminished by 34.3%, while NO_x emissions rose by 6.3% to 755 ppm due to higher combustion temperatures. Response Surface Methodology (RSM) optimization found IT30.25° should be used with 16 LPM H₂ as the best operating condition, which forecasts a brake thermal efficiency of 32.52% and NO_x output at 751 ppm. This work brings an innovative approach by combining biodiesel combustion enhancement through precise control of hydrogen flow and timing adjustments, which received statistical validation through diagnostic methods. The obtained data create a performance-enhanced pathway to improve efficiency under BS-VI and Euro VI emission standards for CI20-hydrogen blends, which demonstrate potential as efficient decarbonized engine technology solutions.