s chamehsara - Department of Mechanical Engineering, Malek-E-Ashtar University of Technology, Tehran, Iran
s.m mirsalim - Department of Mechanical Engineering, Amirkabir University of Technology, Tehran, Iran

In this study, the effects of fuel injection discharge curve and nozzle geometry with constant fuel rate in heavy duty diesel engine are discussed by AVL-Fire software for simulation of combustion process. At first the fuel injection discharge curve changed from semi-triangular to rectangular which is usual in common rail fuel system. Second the effect of nozzle hole diameter (4, 3.1 and 2.2 millimeter with a rectangular discharge curve) on combustion parameters, especially NOX emission are investigated. In the stage, the NOX emission and the cylinder pressure both decreased about 21% and 8% respectively whereas the special change was not observed in output power and instead the soot emission increased about 16% that these result are for fuel injection discharge curve; On the other hand, by decreasing in nozzle hole diameter in the best condition, the NOX emission decreased about 28% while the soot emission increased about 20%.

CFD Simulation, HD diesel engine, Nozzle geometry, NOX emission, Fuel injection discharge curve, combustion process