Authors: Rafiu K. Olalere, Y.O Bankole, Hongming Xu, Animashahun L. A, Sheriff Lamidi
Abstract: The increasing demand for cleaner and more sustainable transportation fuels has intensified interest in renewable oxygenated fuels capable of improving the combustion and emission characteristics of gasoline direct-injection (GDI) spark-ignition engines. This study presents a comparative experimental investigation of the combustion behaviour, engine performance, and gaseous emissions of commercial unleaded gasoline (ULG95) and absolute ethanol in a spray-guided GDI engine. Experiments were conducted under stoichiometric operating conditions (λ = 1) at an engine speed of 1500 rpm over an indicated mean effective pressure (IMEP) range of 3.5–8.5 bar using optimized spark timing. Combustion characteristics were evaluated through in-cylinder pressure analysis, coefficient of variation of IMEP (COVIMEP), combustion phasing (MFB50), combustion duration, combustion efficiency, indicated thermal efficiency, and indicated specific fuel consumption. Regulated gaseous emissions comprising carbon monoxide (CO), unburned hydrocarbons (HC), and nitrogen oxides (NOₓ) were also measured and compared. The results demonstrate that ethanol produced higher peak cylinder pressures, shorter combustion durations, improved combustion stability, and higher combustion and indicated thermal efficiencies than gasoline throughout the investigated load range. The superior combustion characteristics of ethanol were attributed to its inherent oxygen content, higher octane rating, and greater resistance to knock, which enabled optimum combustion phasing without knock-limited spark retard. Ethanol also produced substantially lower CO and HC emissions than gasoline, although differences in NOₓ emissions reflected variations in combustion temperature and ignition characteristics. Overall, the study demonstrates that ethanol offers significant advantages in combustion quality and exhaust emission reduction, highlighting its potential as a sustainable fuel for future high-efficiency GDI spark-ignition engines.
DOI: http://doi.org/10.5281/zenodo.21714967
