Sustainability-oriented experimental and GRA–ANOVA optimization of ethyl acetate/ n -butanol/nitromethane gasoline blends in a spark-ignition engine

This study experimentally investigated and optimized the effects of gasoline blends containing ethyl acetate, n -butanol, and nitromethane on the performance, exhaust emissions, noise, and vibration behavior of a single-cylinder spark-ignition engine. A sustainability-oriented multi-domain optimization framework was employed to quantify trade-offs among fuel economy, performance, emissions, and noise–vibration responses and assess optimum robustness. Experiments were conducted using pure gasoline and 12 gasoline-based blends under full-throttle conditions at 1200–2800 r/min. Fuel effects depended strongly on engine speed and blend composition. At 2000 r/min, G97EA1NB1NM1 reduced brake-specific fuel consumption by 9.49%, while G94EA6 reduced brake-specific energy consumption by 12.42% and increased thermal efficiency by 13.52%. At 2400 r/min, G94NB3NM3 reduced CO by 58.33%, while G97NB1.5NM1.5 reduced hydrocarbons by 23.65%. G94EA3NB3 achieved the greatest NO x reduction (74.10%) at 2800 r/min, although some nitromethane-containing blends substantially increased NO x . Noise changes remained limited, whereas G94EA3NB3 reduced vibration by 16.60% at 2800 r/min. Gray relational analysis identified G94EA3NM3–1600 r/min as the overall and performance-based optimum and G94EA3NB3–2800 r/min as the emission and noise–vibration-based optimum. Independent validation tests using freshly prepared fuel blends yielded mean absolute relative deviations of 0.40–1.01% across the four optimization groups, supporting reproducibility. Analysis of variance identified engine speed as the dominant factor in all optimization groups, while fuel type significantly affected overall, performance, and emission-based results.