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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 μm). 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.

Turbulence modeling for fuel spray simulation plays a prominent role in the understanding of the flow behavior in Internal Combustion Engines (ICEs). Currently, a lot of research work is actively spent on Large Eddy Simulation (LES) turbulence modeling as a replacement option of standard Reynolds averaged approaches in the Eulerian-Lagrangian spray modeling framework, due to its capability to accurately describe flow-induced spray variability and to the lower dependence of the results on the specific turbulence model and/or modeling coefficients. The introduction of LES poses, however, additional questions related to the implementation/adaptation of spray-related turbulence sources and to the rise of conflicting numerics and grid requirements between the Lagrangian and Eulerian parts of the simulated flow.

In the present paper are examined the consequences of a substantial rise in the injection pressure for Gasoline Direct Injection (GDI) injector assemblies. The paper presents a comparative study of the spray behavior of two different injector nozzle layouts submitted to current 10 Mpa rail-pressure as well as to a 30 Mpa injection pressure. To evaluate the differences in the fundamental physical spray parameters are used several specially developed optical visualization techniques, which enable phase-Doppler, PIV, Laser-sheet and high-speed recordings of dense high pressure fuel sprays. A recently developed injector actuator and the necessary modifications to existing high-pressure pumps to reach a 30 MPa pressure level in the fuel system are presented. The change in basic spray parameters (time-resolved droplet distribution and spray momentum) caused by the rail-pressure rise is examined.