Impact of Hydrogen Energy Share and Spark Ignition Timing on Combustion Behavior, Performance, and Emissions of a Gasoline Engine

This study investigates experimentally the impact of hydrogen energy share (HES) and ignition timing (IG) on the combustion, performance, thermal behavior, and emissions of a hydrogen-gasoline dual-fuel spark-ignition engine. Experiments were conducted at a fixed engine speed of 1500 rpm, with hydrogen enrichment varied from 0% to 40% by energy share. Ignition timing was adjusted between 14 deg crank angle (CA) and 18 deg CA before top dead center (BTDC). The results showed that increasing HES to 40% led to an earlier mass fraction burned (MFB), a shorter burn duration, and increases in peak in-cylinder pressure and maximum pressure rate (MPR) by up to 22.6% and 56%, respectively. The peak heat release rate (HRR) also increased by up to 14.6%. The indicated mean effective pressure (IMEP) peaked at 10% HES but declined thereafter due to reduced volumetric efficiency. Brake specific fuel consumption (BSFC) decreased across all ignition timings by up to 18%, while brake power showed only minor reductions. Indicated thermal efficiency (ITE) improved significantly, reaching up to 32.5% at 40% HES. Emission analysis revealed substantial reductions in carbon dioxide (CO2) (19.3%), carbon monoxide (CO) (41.9%), and hydrocarbon (HC) (14.6%) with increasing HES, attributed to enhanced combustion efficiency and a lower concentration of carbon species in the fuel-air mixture. However, nitrogen oxide (NOx) emissions increased by 60% due to elevated flame temperatures. These findings highlight the importance of optimizing hydrogen enrichment and ignition timing to improve engine performance and efficiency while effectively managing emissions in dual-fuel operation.