Numerical Simulation for Combustion and Emission of an Engine Fueled with Biodiesel

For a vertical, straight,water cooled, four stroke, electronically controlled direct injection, high pressure common rail, high pressure common rail, and high pressure diesel engine with exhaust gas hypass valve, threedimensional combustion process simulation models were established with the method of combining computational fluid dynamics (CFD) software AVL-FIRE and experiment. Effects of combustion process, emission formation and exhaust gas recirculation (EGR) rate on the emission of biodiesel engine were simulated.The results show that compared with pure diesel oil, biodiesel combustion has a shorter ignition delay and earlier ignition, cylinder pressure curve ahead, and the combustion duration is slightly longer; compared with the pure diesel engine, the biodiesel engine soot emissions are significantly lower, and the nitrogen oxides (NO_x) emissions increase slightly; EGR can significantly reduce NO_x emissions of biodiesel engine under the condition of no significant impact on soot emission, which indicates that the biodiesel engine can enhance the tolerance of EGR.