Characterization of Gasoline and E85 Direct Injection Sprays in a Constant Volume Vessel Under Late Cycle Engine Conditions

Spray characteristics of a high pressure gasoline direct injector were studied in a constant volume optical combustion vessel over a range of charge gas composition, pressure and temperature conditions for gasoline and E85. The fuel injector was a Bosch GDI injector, with fuel delivery provided through a high pressure accumulator supply system. The conditions were selected to match those for late injection timing during the compression stroke. To simulate the in-cylinder conditions, the combustion chamber temperatures and pressures were varied from 30°C to 305°C and from 1.8 bar to 9.2 bar respectively. Injection pressure was held constant at 30 bar. Injector and thus initial fuel temperature was controlled independently of the ambient conditions at 50°C. Simultaneous images were taken using Schlieren, laser luminescence and Mie scattering diagnostics. It was found that penetration and spray angle are primarily dependent on charge density, and vaporization is dependent on both charge density and charge temperature. The gasoline sprays are shown to have increased vaporization and higher penetration in comparison to E85.