Simulation of Combustion in a DI Diesel Engine Operating on Biodiesel Blends

Abstract

There has been considerable interest in recent years in using blends of petroleum diesel and biodiesels in diesel engines. Some of the interests arise in making use of renewable fuels, or in reducing dependency on imported fossil fuels and, in some cases, to provide economic boost to agricultural industry. It is believed that substitution of a small amount of biodiesel for petroleum diesel can reduce the import of fuel and help in trade balance. Biodiesels, whether derived from vegetable oils or animal fat, have many properties that align with those of petroleum diesel. This makes biodiesel a good candidate for blending it in small quantities with petroleum diesel. Studies have shown biodiesel blends to work well in diesel engines. However, experimental investigations of biodiesel blends have shown some discrepancies in engine thermal efficiency and emissions of NOx. A combustion simulation model for diesel engine may help to understand some of the differences in engine performance when different fuels are used. This paper deals with an existing simulation model that was applied to a diesel engine operating on biodiesel blends. The model was a modified version of GT-Power that was specifically modified to fit the test engine. The model was calibrated using a single cylinder, naturally aspirated, DI diesel engine operating on ultra-low sulfur (ULSD) diesel. It was used to predict engine performance when operating on different blends of soy biodiesel and ULSD. The simulation utilized detailed physical and chemical properties of the blends to predict cylinder pressures, fuel consumption, and emissions of oxides of nitrogen (NOx). Comparison between predicted and experimental values showed good correlations. The predicted trends in fuel consumption, emissions of NOx and smoke showed comparable trends. The model allows the user to change fuel properties to assess the impact of variations in blend composition on exhaust emissions. This paper discusses comparisons between the predicted and experimental results and how fuel composition can possibly impact NOx emissions.