Sustainable Optimization of Emissions and Performance in Hydrogen Port Injection Diesel Engines Through Port Timing and Injection Duration Modulation

ABSTRACT This study evaluates a single‐cylinder hydrogen port injection (HPFI) Diesel engine by systematically varying the hydrogen port‐injection timing and duration to identify settings that enhance overall operation. The objective is to enhance overall engine performance, strengthen combustion characteristics, and reduce harmful exhaust emissions while maintaining a constant operating speed of 1500 rpm under load conditions ranging from 0% to 100%. A structured test matrix was employed in which the hydrogen injection timing was varied from 6° BTDC to 12° ATDC, and the injection duration was adjusted between 9° and 54° crank‐angle degrees. This operating window enabled a systematic assessment of combustion behavior under dual‐fuel conditions. The most favorable response was obtained when hydrogen was introduced at TDC with a 54° CA injection duration. At this setting, the HPFI diesel engine achieved a brake thermal efficiency of 28.58% at 75% load , a notable improvement over the 18.86% observed with pure diesel. The overall fuel demand also decreased, with TEC dropping from 1.01 kJ/h under diesel operation to 0.66 kJ/h at full load. Emission measurements further highlighted the advantages of hydrogen enrichment, including reduced smoke opacity, improved combustion phasing, and a slight rise in peak cylinder pressure attributable to the faster premixed burn of hydrogen. At 75% load, NOx levels fell from 505 ppm with diesel to 433 ppm under hydrogen‐assisted operation, indicating reduced thermal NOx formation. These findings demonstrate that carefully tailoring hydrogen port‐injection timing and duration can simultaneously enhance performance, combustion efficiency, and emissions.