Performance and emission of a diesel engine using different water/waste fish oil (WFO) biodiesel/diesel emulsion fuels: Optimization of fuel formulation via response surface methodology (RSM)

In the present study, the waste fish oil (WFO) was used to produce biodiesel, at first. Then, different formulations of water/WFO biodiesel/diesel emulsion fuels were prepared by ultrasound irradiation. Afterwards, the performance and exhaust emission of a single-cylinder diesel engine were investigated using different formulations of the emulsion fuel in the fixed engine speed (1800 rpm) under full load condition. The effect of water content (in the range of 3-7%), WFO biodiesel content (in the range of 3-7%), and surfactant content (in the range of 1-2%) was studied using response surface methodology (RSM). Based on multi-objective optimization considering the engine performance and emission factors, the best formulation of the emulsion fuel was found to be 3% WFO biodiesel, 6.13% water, and 1% surfactant. The engine performance and exhaust emission were compared for the best emulsion fuel and neat diesel fuel. Regarding the performance parameters, 6.33% decrease in the engine torque, 7.86% decrease in the engine brake power, and 9.52% increase in the brake specific fuel consumption (BSFC) were observed for the best emulsion fuel comparing the neat diesel fuel. Considering the engine exhaust emission, 42.86% decrease in CO emission, 34.02% decrease in unburnt hydrocarbon emission, and 25.53% decrease in nitrogen oxide emission were observed for the best emulsion fuel in comparison with the neat diesel fuel. As the main finding, simultaneous reduction of CO, unburnt hydrocarbon, and nitrogen oxide emission was achieved for the best formulation of the water/WFO biodiesel/diesel emulsion fuel in comparison with the neat diesel fuel.