A focused parametric study on the influence of hydrogen jet on diesel spray combustion in a dual-fuel direct injection configuration under varying impingement conditions

Hydrogen (H 2 )/diesel dual-fuel direct injection engines combine the advantages of reliable diffusion-controlled combustion of H 2 and the high efficiency of compression-ignition engines. However, it is very possible that the jet impingement combustion occurs under the H 2 high-pressure injection conditions. In this study, the effects of H 2 jet on the diesel spray combustion with dual-fuel direct injection under various spray impingement conditions were numerically investigated. The simulation results indicated that compared to diesel direct injection, the ignition of H 2 /diesel dual-fuel direct injection is advanced, since the strengthened turbulence relevant to the H 2 injection enhances the diesel/air mixing under the conditions tested in this study. Moreover, the H 2 jet can take away the fuel vapor around the fuel droplets, thereby accelerating the evaporation process of the droplets. Based on the simulation, a quasi-steady state of H 2 spray flame is quickly established in H 2 /diesel dual-fuel direct injection, and the H 2 at the jet core region is oxidized mainly by diffusing into the high-temperature flame region under the impingement distance of 30 mm investigated in this work. Moreover, the simulation indicates a trend of enhanced C 2 H 2 oxidation with H 2 jet under the spray impingement conditions, but it is mitigated under free spray conditions. • The H 2 /diesel dual-fuel spray impingement combustion was investigated. • The effect of H 2 jet on diesel spray impingement combustion was clarified. • H 2 jet can effectively enhance the fuel evaporation and mixing. • The diesel ignition is advanced with H 2 jet due to the promoted mixing. • C₂H₂ oxidation is promoted by H₂ jet at the impingement distance of 30 mm.