Optimization of Waste Vegetable Oil–Diesel Blends for Engine Performance: A Response Surface Approach

Abstract

The present study valorizes waste vegetable oil (WVO) as a renewable alternative blend fraction of diesel to fuel a compression ignition engine. Response surface (RS) approach is employed to predict engine performance—fuel consumption (FC) and thermal efficiency (TE)—using three factors–three levels of experimental design array. The factors selected for the study are thermal treatment time of WVO (h), WVO fraction in the blend, and engine torque due to load (Nm). The model predictions are well correlated with the experimental data. Based on the D-optimality criterion, the blend containing 0.50 fraction as 47 h thermally treated WVO at an engine torque of 14.72 Nm is the RS model-optimized blend. The experimental outcomes of the optimized blend are FC = 0.5094 kg/h and TE = 23.70%. The suitability of the optimized factor settings established in the study was verified using waste frying oil (WFO) as a diesel blend. The FC and TE of the optimized WVO–diesel and WFO–diesel blends are compared with the literature values. The model-optimized WVO–diesel blend recorded 14.3% and 17.6% lesser CO and NOx emissions, respectively, and is 45% more economical than neat diesel. The direct blending of WVO with diesel and optimization of the blend fraction and the thermal treatment duration of WVO for better engine performance are a novel approach. The work accounted in this report presents a holistic study toward sustainable utilization of WVO in diesel-driven vehicles and can be helpful to various stakeholders.