Experimental validation of a GDI spray model

A computational model and an experimental analysis have been performed to study the atomisation processes of hollow cone fuel sprays from a high pressure swirl injector for gasoline direct injection (GDI) engines. The objective has been to obtain reliable simulations and better understood structure and evolution of the spray and its interaction with air the flow field. The 3D computations are based on the KIVA 3 code in which basic spray sub models have been modified to simulate break-up phenomena and evaporation process. Spray characteristics have been measured using a system, able to gather and to process spray images, including a CCD camera, a frame grabber and a pulsed sheet obtained by the second harmonic of Nd-YAG laser (wavelength 532 nm, width 12 ns, thickness 80 ¼m). The readout system has been triggered by a TTL signal synchronized with the start of injection. A digital image processing software has been used to analyse the collected pictures. Computed and measured spray characteristics, such pre-spray and main-spray structure, tip penetration and break-up phenomena, have been compared, achieving good levels of agreement.