Analysis and optimization of spray angle and hydrogen injection timing effects on performance of a H ₂ -diesel dual-fuel engine

The study employs the RSM-NSGA III mixed optimization method to achieve low emissions at high performance levels, using HA (Horizontal Angle), VA (Vertical Angle), and HIT (Hydrogen injection timing) as decision variables for optimizing the IMEP, soot, and NOx in a coaxial H 2 -diesel dual-fuel internal combustion engine. Initially, a three-dimensional simulation model of a coaxial H 2 -diesel dual-fuel internal combustion engine was established using CONVERGE, and its accuracy was validated with experimental data. Subsequently, grid independence verification determined the maximum grid size. Single-factor analyses for HA, VA, and HIT were performed, followed by BBD (Box-Behnken Design) for experimental design. RSM (Response Surface Method) was then used to build a mathematical model, which was subsequently optimized using NSGA III to obtain Pareto frontiers. The TOPSIS method was employed to select the optimal non-dominated solution from these frontiers. Results show that advancing HIT can effectively improve the mixture of H 2 and diesel, while appropriate HA and VA values facilitate mixing between H 2 and diesel. In contrast, improper angles degrade combustion conditions. Finally, NSGA III successfully yielded the best solution, with the optimal settings being HA = 0°, VA = 17.938°, and HIT = −20°CA ATDC. Compared to HIT-20 condition, the optimized results show that NOx increases by 38.58%, IMEP increases by 2.02%, and soot decreases by 56.99%. This study provides technical and practical insights into the optimization design of H 2 -diesel dual-fuel engines in terms of timing and spatial coordination.