Department of Mechanical Engineering, College of Engineering, Islamic Azad University, Tehran South Campus, Iran.
10.30772/qjes.2026.172099.2021
Abstract
This study experimentally investigates the effect of hydrogen enrichment on combustion characteristics, engine performance, and exhaust emissions of a four-stroke spark-ignition (SI) gasoline engine. A single-cylinder, 0.61-L, air-cooled engine was operated at 2300 rpm under full load with hydrogen blending ratios of 5%, 10%, 15%, and 20% by fuel energy, using unleaded gasoline (RON 95) as the base fuel. Hydrogen was delivered through a dedicated port injector upstream of the intake valve. Peak cylinder pressure increased by 17.6% (4.82 to 5.67 MPa at H20%), and the 10–90% mass-fraction-burn duration decreased by 31.6% (38 to 26 °CA), driven by hydrogen’s high laminar flame speed (237 cm/s) and wide flammability range (4–75 vol%). Brake thermal efficiency peaked at H15% (32.1%, +12.6%), while brake-specific fuel consumption fell by 17.35% at H20%. Combustion stability improved by 60.7%, with COV of IMEP reduced from 2.8% to 1.1%. CO, HC, and CO₂ emissions decreased by 81%, 66.5%, and 25%, respectively, with the average unburned-HC carbon chain length reduced from C₆.₂ to C₃.₁. However, NOx emissions rose by 338.7% due to higher peak combustion temperatures activating the thermal (Zeldovich) mechanism. The optimal blending ratio is 10–15%, balancing efficiency gains against NOx penalties addressable through established aftertreatment strategies.
Mohammed,H K.. (2026). Effect of hydrogen enrichment on combustion characteristics and emissions of a four-stroke gasoline engine. (e192153). Al-Qadisiyah Journal for Engineering Sciences, (), e192153 doi: 10.30772/qjes.2026.172099.2021
MLA
Mohammed,H K.. "Effect of hydrogen enrichment on combustion characteristics and emissions of a four-stroke gasoline engine" .e192153 , Al-Qadisiyah Journal for Engineering Sciences, , , 2026, e192153. doi: 10.30772/qjes.2026.172099.2021
HARVARD
Mohammed H K.. (2026). 'Effect of hydrogen enrichment on combustion characteristics and emissions of a four-stroke gasoline engine', Al-Qadisiyah Journal for Engineering Sciences, (), e192153. doi: 10.30772/qjes.2026.172099.2021
CHICAGO
H K. Mohammed, "Effect of hydrogen enrichment on combustion characteristics and emissions of a four-stroke gasoline engine," Al-Qadisiyah Journal for Engineering Sciences, (2026): e192153, doi: 10.30772/qjes.2026.172099.2021
VANCOUVER
Mohammed H K.. Effect of hydrogen enrichment on combustion characteristics and emissions of a four-stroke gasoline engine. QJES. 2026;():e192153. doi: 10.30772/qjes.2026.172099.2021
