Effects of hydrogen addition in intake air on combustion and emission of diesel engines

To assess the feasibility of hydrogen as a substitute for diesel, the impact of hydrogen addition into intake air on diesel engines was examined numerically using GT Power software at various operating conditions. The original engine is a four-cylinder turbocharged diesel engine, which is modified into a hydrogen diesel dual-fuel (HDDF) engine with an injection of hydrogen into the intake port and a direct injection of diesel into the cylinder. Engine speeds are set at 1600, 2300, and 3600 rpm, while the engine loads are set at 25%, 50%, and 75%, respectively. H2 energy ratio (HER) varies from 0% to 60% at an interval of 10%. The results demonstrate that as the HER increases, the peak cylinder pressure (PCP) decreases, while the peak cylinder temperature (PCT) increases, the indicated mean effective pressure (IMEP) and indicated thermal efficiency (ITE) increases, while the ignition delay period shortens. Among them, the PCP is reduced by 4–7%, and the ITE is increased by 2–3.5%. In terms of emissions, CO and HC emissions are significantly decreased under all operating conditions, but for NOx emissions, NOx emissions remain unchanged (within a range of 7%) under most operating conditions, except for the increase in NOx emissions under high-speed and high-load conditions.