A Numerical Study and Optimization of GDI Engine Parameters for Better Performance and Complete Combustion Using KIVA-3V and VISUALDOC® 2004-01-3008

With many advantages of GDI technology, one major disadvantage is high HC emissions. The primary goal of this study is to determine the optimum values of engine parameters that would result in maximum power output from a GDI engine, with complete combustion, minimum hydrocarbon (HC) emissions, and minimum specific fuel consumption. A two-dimensional engine geometry with a piston-bowl was selected for faster engine CFD simulations. The first part involves a study of the affect of engine parameters on performance and HC emissions. The parameters considered were, equivalence ratio (mass of injected fuel), injection timing, ignition timing, engine RPM, spray cone angle, and velocity of fuel injection. The second part of the study involves determining the optimum values of fuel mass injected, injection timing, and ignition timing in order to maximize power output while limiting the amount of fuel left unburned after the end of the expansion process. The optimization procedure was automated by linking the optimization software VisualDOC^® to the output from the engine CFD simulation software KIVA-3V. A computer program was developed to link the two software together. Various optimization methods, parameters and constraints were used in VisualDOC^® to achieve accurate and faster optimization results.