In this study, a novel dual-fuel combustion strategy is investigated, employing
late pilot injection in diesel–methane engines to improve performance and reduce
emissions. The engine was first tested with conventional diesel and methane,
exploring a wide range of pilot injection timings, injection pressures, and
intake boost pressures. Subsequently, experiments were repeated using a
methane/hydrogen blend to assess the influence of hydrogen addition. Results
show that, when using only methane, delayed pilot injections have minimal
effects on engine performance. In naturally aspirated operation, unburned
hydrocarbons and carbon monoxide are reduced, while in supercharged conditions,
emissions increase; however, they remain within acceptable limits. Nitrogen
oxides and particulate matter reach their lowest levels with delayed injection.
Introducing hydrogen reduces engine performance and hydrocarbons and carbon
monoxide emissions; notably, it suppresses the typical nitrogen oxides increase
associated with hydrogen, while also lowering particulate matter. These findings
demonstrate that combining late pilot injections with hydrogen addition and
supercharging is a promising strategy for improving dual-fuel engine efficiency
and emissions, offering a potential pathway toward cleaner combustion.
