CFD optimization for GDI spray model tuning and enhancement of engine performance

Coupling a 3D Computational Fluid Dynamics (CFD) tool with a rigorous method of decision making is becoming indispensable in the design process of complex systems, as internal combustion engines.CFD based optimization (CFD-O) is here carried out on a single cylinder, four-valve, four-stroke gasoline direct injection (GDI) engine, to enhance mixture formation under stratified charge operation, hence to choose between the single or double injection strategy maximizing the engine power output. A 3D engine model is coupled with the Simplex algorithm to find the optimal synchronization of both injection and spark timing within the working cycle.CFD-O is also addressed to perform the validation of the gasoline spray model, that otherwise reveals tedious and time-consuming. The Simplex algorithm is used to tune the constants entering a model developed by authors, as applied to three different high pressure GDI injectors, preliminary experimentally characterized.Fully automatic procedures are assessed to be exploited in the phase of engine design, whose contribution may be of great importance to reduce development costs and time-to-market of new technologies.

► Two examples of CFD based optimization in the design of a GDI SI engine are given.
► The Simplex algorithm is used to automatically validate a GDI spray model.
► Portability of the model to three different GDI multi-hole injectors is proven.
► Optimization of the mixture formation to minimize a GDI engine consumption is also realized.
► Optimal double injection reduces fuel consumption more than single injections.