Effects of Ethanol-Gasoline Blending on Combustion, Performance, and Emissions of a Spark Ignition Engine: An Experimental and Detailed Chemistry-Based Numerical Study

This study investigates experimentally and numerically the impact of e-ethanol drop-in on combustion, performance, and emission metrics in a single-cylinder spark ignition engine. Experiments were conducted at a constant compression ratio of 9, 75% throttle, engine speed of 1500 rpm, equivalence ratio of 0.81, and fixed ignition timing of 25 °CAD BTDC. Numerical simulations utilizing both a global single-step reaction model for pure gasoline (G100) and a detailed chemical mechanism for G100 and different ethanol blends provided accurate predictions of combustion trends. Blending ethanol up to 30% by volume (E30) enhances combustion quality, as evidenced by increased in-cylinder pressures and improved IMEP. However, ethanol concentrations beyond E40 led to combustion instability and significant losses in pressure and efficiency due to suboptimal combustion phasing supported by lower heating value. The analyses of the thermal and flow fields revealed consistent intake-induced tumble motion and similar in-cylinder velocity structures for E100 and G100, regardless of the blend ratio. E30 offered the lowest indicated specific fuel consumption of 380 g/kWh and the highest indicated thermal efficiency (η_th, I) of 34.5%. Emission trends favored ethanol addition, with reductions in CO₂ by 16%, CO by 27%, NO_x by 38%, and unburned hydrocarbons by 57% for E60 in comparison with G100 attributing to ethanol’s oxygenation.