Spray atomization characteristics of a GDI injector equipped with a group-hole nozzle

Abstract

The main purpose of this paper is to analyze the spray characteristics of a group-hole nozzle in terms of spray behavior and atomization process in comparison to the characteristics of a single-hole nozzle as reference. Spray visualization and PDPA (phase Doppler particle analyzer) experiments were performed using a GDI adjustable injector, which can adopt a different type of nozzle at free spray conditions. By analyzing the spray development behavior and distribution of droplet velocity and diameter based on a time series, and comparing these results with that of a single-hole nozzle, the effects of the group-hole nozzle on the spray characteristics in a GDI injection were elucidated.Experimental results showed that the development processes of spray behavior from a group-hole nozzle were similar to that of the single-hole nozzle. Both the sprays had similar spray tip penetration and dispersion at the same stages of development. However, owing to the constant spray momentum from a spray interaction, the spray behavior from the group-hole nozzle seemed to be more stable than that of the single-hole nozzle. In terms of the averaged droplet size, the group-hole nozzle held an advantage over the single-hole nozzle in decreasing Sauter mean diameter (SMD) by approximately 2μm. In addition, in comparison to the spatial distribution of droplet diameter and velocity between them, it can be confirmed that the group-hole nozzle has strong effects on reduction in diameter as well as rapid dispersion of droplet due to active air entrainment. These atomization characteristics are considered as an important advantages for improving mixture formation in GDI engine.