Performance, emission, and combustion trade-off optimization of hydrogen-diesel dual-fuel CI engine using response surface methodology

The growing need for carbon-neutral fuels to mitigate global warming has intensified interest in hydrogen (H₂) and its integration into advanced diesel engine technologies. This study experimentally investigates an optimized operating strategy for a single-cylinder compression-ignition engine functioning in hydrogen–diesel dual-fuel mode, employing Port Fuel Injection of H₂ with Direct Injection of diesel. The objective is to enhance combustion efficiency, reduce greenhouse emissions, and improve the sustainability of diesel-based powertrains. Engine tests were conducted at 1500 RPM under varying loads and hydrogen substitution levels (DH0–DH3), supported by Response Surface Methodology for performance–emission optimization. Hydrogen addition significantly improved fuel reactivity due to its high diffusivity and rapid flame speed, yielding a maximum BTE improvement of 23% at full load under DH3, accompanied by NOx levels of 7.5 g/kWh. While hydrogen lowered soot and UHC emissions at moderate loads, incomplete oxidation at low loads increased UHC formation. A multi-objective optimization using a desirability function and Central Composite Design produced predictive models with ≤3% error. The optimal setting—50% load and 6500 μs injection duration (DH2)—resulted in BTE 24.45%, volumetric efficiency 70.85%, UHC 5.46 g/kWh, NOx 2.40 g/kWh, soot 0.245 g/kWh, and desirability 0.83, demonstrating hydrogen's strong potential as a clean, sustainable diesel alternative. This work directly contributes to the United Nations Sustainable Development Goals by advancing clean energy solutions (SDG 7), fostering sustainable industrial innovation in engine technologies (SDG 9), and supporting climate action through reduced carbon-intensive combustion strategies (SDG 13).