Engine performance and emission optimization of waste cooking oil/diesel/n-octanol blends via response surface methodology

Waste cooking oil (WCO) presents a viable and sustainable alternative for diesel engines; however, its higher viscosity limits its direct use. The incorporation of higher alcohols, such as n-octanol, improves fuel properties without requiring transesterification. This study systematically investigates the combined effects of engine load and n-octanol concentration on the performance and emission characteristics of a 10-kW stationary diesel engine fueled with diesel-WCO-n-octanol blends, employing a full factorial experimental design coupled with response surface methodology. Statistically significant regression models were developed for BTE, BSFC, CO, NOX, HC, CO2, EGT, and smoke, with prediction errors within ±8%. The optimized D50W30O20 blend at 65% engine load achieved the highest desirability (0.988), reducing CO, NOX, HC, and smoke emissions by 5.70%, 33.56%, 12.24%, and 22.85%, respectively, compared to neat diesel, while maintaining comparable BTE. The results demonstrated the feasibility of alcohol assisted WCO blends for the cleaner operation of a diesel engine.