Effect of Isopropanol–Butanol–Ethanol (IBE) Direct Injection Strategy on Combustion and Emission Characteristics of a Gasoline Port Injection SI Dual-Fuel Engine

Under the dual-carbon goals, adopting renewable alternative fuels in transportation is crucial. Alcohol-based fuels, produced via biomass fermentation or green electricity-powered CO2 hydrogenation, offer benefits like renewability, engine compatibility, and long driving range. Bio-butanol, with an energy density close to gasoline, can power SI engines directly, but its high production costs due to low fermentation efficiency limit its viability. In contrast, IBE (a butanol fermentation intermediate) avoids costly separation steps, making it more competitive than pure butanol. Existing research on IBE in spark ignition engines mainly focuses on fixed-ratio IBE-gasoline blends, restricting real-time fuel adjustment. Building on prior findings that IBE outperforms ABE and butanol, this study examines the combustion and emission characteristics of a gasoline port injection + IBE direct injection engine under varying direct injection timings, IBE ratios, and excess air ratios. Research indicates that early direct injection timings with pure IBE provide optimal performance at stoichiometric conditions. As the excess air ratio rises, an 80% IBE direct injection ratio becomes more advantageous. IBE shows great promise as an alternative fuel, enhancing combustion performance and reducing gaseous and particulate emissions.