Combustion characteristics and engine emissions of a diesel engine fueled with diesel and treated waste cooking oil blends

In this study, waste cooking oil from restaurants was used to produce a renewable and sustainable biodiesel through transesterification process. The Treated Waste Cooking Oil (TWCO) fuel produced has shown very promising chemical and physical properties; most notably; cetane number (∼49) and sulphur content (8mg/kg). The combustion of conventional diesel and Treated Waste Cooking Oil (TWCO)-diesel blend (50/50 by volume; shown as TD50) was examined at different engine conditions. The combustion of TD50 resulted in a considerable reduction in the smoke opacity and unburnt hydrocarbons associated with an increase in the CO₂ and NO_x emissions due to unintentional advance of fuel injection timing, caused by the higher bulk modulus of TD50 fuel. Results indicated an increase in brake specific fuel consumption with simultaneous reduction in the engine thermal efficiency compared to conventional diesel. The lower smoke opacity in the case of TD50 fuel assists NO_x reductions by exploiting the higher EGR tolerance of TD50 fuel. Thus, a more encouraging NO_x-smoke tradeoff may be selected to reduce both NO_x and smoke. The effect of EGR in NO_x reduction was more noticeable with TD50 than conventional diesel fuel.