Investigation of hydrogen addition in diesel/n-butanol blended fuel for diesel engines: Combustion, emissions, and multi-objective optimization

Hydrogen, as a promising alternative fuel, has received increasing attention for its potential to improve combustion and reduce fossil-fuel consumption in diesel engines. In this study, a validated numerical model of a diesel engine based on previous experimental data is used to study the effect of hydrogen on the combustion and emissions of a dual-fuel engine. First, a CONVERGE model was applied to investigate the combustion and emissions of diesel/n-butanol/hydrogen blends. Thereafter, the RSM and NSGA III were applied to predict and derive the Pareto frontiers, with NO x , soot, and HC emissions as the optimization objectives and the n-butanol ratio, hydrogen ratio, and injection timing as the decision variables. Ultimately, using the TOPSIS method to identify the optimal solution. The results indicate that both n-butanol and hydrogen contribute to increase in-cylinder pressure, HRR, and peak in-cylinder temperature at mid-to-high loads. Additionally, hydrogen reduces the ignition delay caused by n-butanol's high latent heat of vaporization. Regarding emissions, both n-butanol and hydrogen contribute to the reduction of soot and HC emissions under mid-to-high loads, albeit at the cost of increased NO x emissions. However, at 25% load, hydrogen addition partially alleviates NO x emissions, primarily because its combustion becomes less complete under low load conditions. The multi-objective optimization successfully reduced NO x and soot emissions by 5.3% and 60.3% respectively, while HC emissions increased by 26.7% due to the trade-off relationship. This study holds significant implications for optimizing internal combustion engines, reducing carbon emissions, and minimizing fossil fuel consumption. • Diesel/n-butanol/hydrogen blended fuel combustion and emissions are investigated. • Hydrogen addition enhances combustion at mid-to-high loads. • RSM-NSGA III algorithm is used to optimize blending ratio and injection timing. • Optimization lowers NO x by 50.33 ppm and soot by 11.05 ppm.