Impact of butanol and hexanol on RCCI engine efficiency and emission characteristics using sapota oil methyl ester and response surface methodology.

This research explores the performance, emissions, and combustion behavior of a dual-fuel Reactivity Controlled Compression Ignition (RCCI) engine fueled with sapota oil methyl ester (SOME) blended with butanol, hexanol, and diesel. Sapota oil methyl ester, a still less-researched biodiesel, is evaluated for its synergistic effect when blended with oxygenated additives. Using Response Surface Methodology (RSM), some of the fuel blends like a base blend (B20D80) and others like B20BU10D70 and B20HEX10D70 were compared to enhance engine efficiency and emissions. The findings show that Brake Thermal Efficiency (BTE) increases with engine load, with Further gains detected under oxygenated blends. With a 10% butanol addition, the BTE improved by about 0.30%, while hexanol blends showed as much as a 0.70% improvement over the reference B20 blend. At the same time, Brake Specific Energy Consumption (BSEC) reduced by 3.29% for butanol and 4.5% for hexanol blends, reflecting improved energy efficiency. Emissions analysis showed that hydrocarbon (HC) and carbon monoxide (CO) emissions have reduced oxygenated additives. With 10% concentrations, HC emissions were reduced by 2.27% (butanol) and 4.65% (hexanol), and the co emissions fell 50% and 63%, respectively. Carbon dioxide (CO₂) increased with load due to incomplete combustion initially, but later reduced in high loads. Smoke emissions were equally reduced by 3.23% (butanol) and 6.66% (hexanol) at 10% levels but increased with increased alcohol content. But emissions did not increase a Little by 1% for butanol and 4.5% for hexanol, emphasizing the need to adopt a careful approach to mixture formulation to deal with environmental concern. The combustion test validated that moderate levels of butanol and hexanol enhance combustion efficiency through enhanced oxygen supply and atomization. The research concludes that B20 + BU10 + D70 and B20 + HEX10 + D70 blends are a viable direction towards sustainable fuel utilization by striking a balance between performance improvement and emission regulation. This work provides insightful contributions towards the optimization of biodiesel-alcohol-diesel blends for clean and efficient engine operation.