INNOVATIVE HIGH-PRESSURE GDI SPRAYS CHARACTERIZED AT ENGINE-LIKE CONDITIONS

The direct injection of fuel in the combustion chamber of spark ignition (SI) engines is spreading more and more, because it allows a better control of the fuel consumption in comparison to port fuel injection engines. The challenge remains the improvement of the spray parameters in terms of atomization, smaller droplets and their spread in the combustion chamber in order to enhance the combustion efficiency. In this framework, one of the most established approaches is the increase of the fuel injection pressure to improve combustion efficiency and lower engine-out emissions. In this work, the effects of very-high injection pressure (up to 100 MPa) on gasoline spray development will be discussed for a wide range of ambient conditions, including sub-atmospheric ones. Liquid and vapor fuel phases were investigated under evaporative and non-evaporative conditions by a multi-hole GDI injector in a constant volume vessel filled with gas (N2) at diverse pressures and temperatures. The investigation by optical techniques, using a highspeed C-Mos camera, permitted to depict the liquid propagation in a cycle-resolved way through Miescattering, and the global one (liquid + vapor phase) through the shadowgraph technique