Experimental study on spray characteristics under ultra-high injection pressure for DISI engines

Abstract

In order to provide comprehensive information on gasoline spray characteristics under ultra-high fuel injection pressure for direct-injection spark-ignition engines, the macroscopic characteristics of gasoline sprays for both liquid and vapor phases, including overall spray structures, spray tip penetrations, and spray angles, were determined simultaneously via Laser Absorption-Scattering technique under non-vaporizing and vaporizing conditions. Empirical correlations of spray tip penetration for transient gasoline sprays were obtained and compared with those for diesel sprays. Experimental results showed that under non-vaporizing conditions, spray tip penetration was approximately proportional to time. Under vaporizing conditions, the spray plumes were compressed axially and expanded radially; fuel vapor was concentrated in the spray head, while fuel droplets in the tail. Vapor phase spray tip penetration shared similar values and temporal variations with liquid phase but with a subtle and regular difference. In contrast with diesel sprays, gasoline spray penetration of liquid phase showed larger dependence on ambient gas density and smaller dependence on fuel pressure drop through injector. Compared with liquid phase, vapor phase penetration showed a larger growth rate with time and presented a smaller falling slope against ambient gas temperature.