Investigation of change of NOx and soot emissions using biodiesel and diesel fuel with metallic additive in a diesel engine

With the use of biodiesel as an alternative fuel in diesel engines, achieving a significant reduction in exhaust emissions especially incomplete combustion products, NOx emissions are generally higher than for petroleum-based diesel. It is known that soot formation during combustion is reduced due to the molecular oxygen content of biodiesel fuels. This situation affects radiation heat transfer in combustion chamber and thus mean flame temperature; therefore, the NO formation, which is strongly depended on the chamber temperature, is affected by soot formation in combustion chamber in case of using biodiesel. In this study, in a diesel engine fueled with petroleum diesel, the investigation of the change in NO formation is aimed in case of operating conditions, which same with biodiesel use, obtaining similar soot formation as biodiesel. For this purpose, to reduce soot formation in case of using petroleum diesel, soot formation was reduced to a rate that is similar to biodiesel use by the method of the addition of metallic additives to petroleum diesel fuels. In the study, additive was synthesized from metallic barium and the synthesized additive was added to the petroleum based diesel fuel in a volume ratio of 0,25%, 0,50% and 1%. Petroleum based diesel, soybean oil based biodiesel and petroleum based diesel with additive have been tested in a three-cylinder, direct-injection diesel engine at constant speed and under varying load conditions. As a result of the experiments; specific fuel consumption values of additive test fuels are similar to diesel fuels, while increase in specific fuel consumption values of biodiesel is observed. There was a decrease in the effective yield of biodiesel compared to petroleum-derived diesel and diesel fuel with additive. As a result of the emission tests, an increase in NOx emissions of pure biodiesel was observed, but the contribution of the additive diesel fuels decreased significantly According to the results obtained in the study, it was understood that although the Ba additive effectively reduces smoke emissions, it does not have an effective role on NOx formation. Petroleum based diesel fuel with 1% barium additive, 5.2% and 15% smoke emissions were measured in the case of two different loads, compared to 10.4% and 33% for biodiesel use. In the case of almost equal soot emission condition, NOx emissions have been measured higher in biodiesel use.