Effects of high-ethanol blends on performance and emissions of a spark-ignition engine with single and dual injector configurations

Effective utilization of high-ethanol fuels in spark-ignition (SI) engines requires injection configurations capable of accommodating significant variations in fuel properties. This study experimentally investigates the performance and emission characteristics of an SI engine fueled with gasoline-ethanol blends (E25, E50, E85, and E100) relative to baseline gasoline (E0), employing singleand dual-port fuel injection configurations. Experiments were conducted at a fixed engine speed of 6500 rpm over a range of load conditions. For consistent fuel-to-fuel comparison, gasoline-defined throttle settings were preserved while the injected fuel quantity and load were adjusted to sustain steady speed. Injector mass-flow characteristics were calibrated for each fuel to ensure accurate delivery. Results indicate that ethanol blends generally increased engine output but resulted in higher brake specific fuel consumption (BSFC) due to their lower heating value. At higher throttle openings (> 32%), gasoline exhibited superior performance. Under part-load conditions (< 28%), E25 combined with dual injection achieved brake power comparable to gasoline while improving brake thermal efficiency and reducing BSFC in both injection modes, reflecting enhanced mixture preparation enabled by ethanol-bound oxygen under low-throttle, low-airflow conditions. Increasing ethanol content significantly reduced CO, HC, NOx, and CO2 emissions, with dual injection providing additional emission benefits through shorter injection duration and improved mixture homogeneity. These findings demonstrate that dual-injector configurations can effectively enhance mixture preparation and reduce emissions when operating with high-ethanol fuels, offering their potential to improve part-load efficiency in SI engines.