10. Advanced Combustion Technologies for Port Fuel Hydrogen Injection and Diesel Pilot Ignition

Hydrogen is an alternative fuel for internal combustion engines (H2ICE). When produced from renewable energy sources, it has the potential to meet future legislation aimed at reducing CO₂ emissions. H2ICE offers advantages such as competitiveness, robustness, long lifespan, and low hydrogen purity requirements, while also demonstrating high efficiency. Among various options, H2ICE in turbocharged compression ignition engines presents a promising approach, enabling the dual-fuel concept. This technology can be adapted to four-stroke engines for automobiles (1000–4500 rpm), ship propulsion (500–1000 rpm), and low-speed engines used for ship transport or power production in a two-stroke cycle. Nevertheless, several challenges must be addressed. These include nitrogen oxide (NOx) production, which limits its applicability in certain sectors, and the occurrence of knock, which restricts mean effective pressure. For NOx control, promising approaches, involving adjustments to compression ratio, bowl shape, exhaust gas recirculation (EGR), injection timing, and water injection (WI), are being investigated. Currently, simulations have demonstrated efficiency levels exceeding 50% for low-speed two-stroke engines and over 35% for high-speed engines, achieved through the appropriate combination of measures to simultaneously control knock and NOx emissions. Furthermore, new developments in combined diesel-hydrogen direct injection for medium-speed engines anticipate an enhancement in the expected performance of this technology.