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This paper illustrates the results of an experimental characterization of a high pressure diesel spray injected by a common rail (CR) injection system both under non-evaporative and evaporative conditions. Tests have been made injecting the fuel with a single hole injector having a diameter of 0.18 mm with L/D=5.56. The fuel has been sprayed at 60, 90 and 120 MPa, with an ambient pressure ranging between 1.2 to 5.0 MPa. The spray evolution has been investigated, by the Mie scattering technique, illuminating the fuel jet and acquiring single shot images by a CCD camera. Tests under non-evaporative conditions have been carried out in an optically accessible high pressure vessel filled with inert gas (N2) at diesel-like density conditions. The instantaneous fuel injection rate, obtained with a time resolution of 10 microseconds, has been also evaluated by an AVL Fuel Meter working on the Bosch Tube principle.

In the modern GDI systems, the optimization of the fuel injection process is essential to prepare an air-fuel mixture capable to promote efficient combustion and reduce fuel consumption and pollutant emissions. A key feature for a better atomization is the fuel injection pressure. The increasing of the injection pressure is considered a good way for particle number (PN) reduction due to improved spray atomization, faster evaporation and better mixture formation. In this paper, a multi-hole GDI injector was tested to investigate the effects of very high injection pressures (IVHP), in addition to different ambient densities and temperatures, on the fuel spray morphology, in a cycle-resolved images analysis. Commercial gasoline was injected at the pressures ranging between 40.0 to 70.0 MPa, at gas densities varying between 1.12 to 11.5 kg/m3, and gas temperature up to 200°C.