Effects of Pre-Injection and Antioxidants in a Diesel Engine Fuelled with Methyl Esters of Waste Cooking Oil Biodiesel

Diesel engines are significant contributors to air pollution, particularly through emissions of nitrogen oxides (NOx), smoke, and carbon monoxide (CO). Finding sustainable fuel alternatives and additives to reduce emissions without compromising engine performance is imperative for environmental and public health concerns. This study investigates the impact of adding tert-butylhydroquinone (TBHQ) antioxidants to blends containing 20% Methyl Esters of Waste Cooking Oil (20MEOWCO) and 80% diesel fuel in Modified Common Rail Diesel (MCRD) engines. The experiment involves adjusting the pilot fuel injection timing to 36°CA bTDC (before Top Dead Centre) and the main injection timing to 15°CA bTDC, with a Nozzle Opening Pressure (NOP) of 500 bar. Biodiesel is produced from used cooking oil using standard procedures and then mixed with diesel fuel. Various concentrations of TBHQ are added to the 20MEOWCO fuel blend for the experiment. The findings indicate that introducing TBHQ in concentrations of 250 ppm and 500 ppm to the 20MEOWCO fuel blend results in a notable reduction of Oxides of Nitrogen (NOx) emission by 13% in MCRD engines. However, this reduction in emissions comes at the expense of increased specific fuel consumption, which is observed to rise by 2.1%. Furthermore, the study highlights a rise in smoke and carbon monoxide (CO) emissions by approximately 7–10% and 5-8%, respectively, under the experimental conditions. The results of this study suggest that the addition of TBHQ to 20MEOWCO blends holds promise for mitigating NOx emissions in MCRD engines.