On the synergistic effects of physical and kinetic interactions in hydrogen-diesel engines

Hydrogen-diesel dual-fuel (HDDF) combustion is a critical path to decarbonize the off-road sector. This research investigates synergistic effects between physical and chemical interactions in HDDF using CONVERGE-CFD. A reduced kinetic mechanism (6 elements, 127 species, 672 reactions) integrating n-dodecane/PAH and hydrogen chemistry was developed and validated against ignition delay times and laminar flame speeds. Results indicate hydrogen kinetics dominate n-dodecane pyrolysis above 40% substitution, shifting combustion from diffusion-dominated to a near-premixed regime at 43.9% H 2 energy share. This evolution is driven by synergistic coupling where hydrogen's high diffusivity enhances turbulent mixing, which in turn accelerates kinetic pathways. Kinetic interactions dominated by hydrogen's radical pool become the primary combustion driver, outpacing physical spray-induced turbulence, which reduces NOx emissions by preventing local high temperatures. These insights hold practical value for off-road machinery decarbonization, where the premixed hydrogen mode enables easy adaptation to existing diesel systems with minimal modifications.