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In GDI engines, the atomization process of the fuel is known to play a key role in affecting mixture formation, combustion efficiency and soot emissions. Multi-hole injectors have been widely used in GDI engines due to their flexibility in controlling jet targeting and fuel distribution. Therefore, successful implementation of GDI technology needs precise knowledge of the fuel injection process and proper understanding of spray characteristics under engine relevant conditions. The injection system needs to improve the spray characteristics in terms of a better fuel atomization in shortest possible penetration length, refined droplet sizes and better droplet size distribution to enhance a combustion system efficiency. In this context, the increasing of the fuel injection pressure seems to play a key role.
This paper reports the results of an investigation on the behavior of gasoline injected at very high-pressure by a GDI injector in a combustion vessel filled with gas (N2) at diverse pressures and temperatures. The injector was a ten-hole nozzle, solenoid-actuated, 0.10 mm in diameter while the injection pressures varied up to 70 MPa, the gas density from 0.2 to 11.50 kg/m3 and its temperature from room to 200°C. The investigation was carried out by optical techniques using a high-speed C-Mos camera and permitting to depict the propagation of the liquid fluid through Mie-scattering and the global (liquid + vapor phases) by shadowgraph technique. The influences of ambient and injection conditions were of particular interest providing fundamental physics insight regarding fuel penetration and vaporization.
