Abstract
The effects of fuel properties, fuel pressure, fuel temperature, and ambient pressure on spray characteristics have been studied extensively by various researchers. Expressed in terms of the primary forces, such as inertia force, surface tension force, viscous force and aerodynamic drag force, many empirical and non-dimensional formulations of spray characteristics such as spray penetration, spray-plume angle, and Sauter Mean Diameter (SMD) have been established. However, these formulations have been primarily developed for use in diesel sprays, and they are generally not directly applicable for spark ignition engine fuel sprays of gasoline and alcohol fuels. In this study, non-dimensional correlations of the microscopic characteristics of the sprays such as drop size for spark-ignition direct-injection (SIDI) engines are obtained in terms of non-dimensional numbers such as the Weber number and Reynolds number. Phase Doppler Interferometry (PDI), combined with Mie-scattered high speed imaging, is applied to measure the drop size distributions of a multi-hole spray over a wide range of test conditions which simulate different operation modes in SIDI engines. Four types of fuels, namely, gasoline, ethanol, butanol and pentanol were used in this study. Based upon the engine conditions, a wide region of Weber number and Reynolds number was chosen to reveal how the dominating forces govern the liquid-jet breakup and spray atomization processes. In addition to the generalized non-dimensional correlations of spray penetration and spray-plume angle for gasoline and alcohol fuels developed in our previous work, the non-dimensional drop size correlations of multi-hole sprays have also been established. Together with the previously derived non-dimensional correlations of spray penetration and spray-plume angle, these generalized non-dimensional correlations of macroscopic and microscopic spray characteristics are found to be very useful for providing the physical insights of modeling the multi-hole sprays in SIDI engine applications.
