The purpose of this study is to improve atomization characteristics of a direct injection Diesel nozzle, which spray with large spray angle, short liquid core length and small droplet diameter are obtained. In the previous study, the single hole atomization enhancement nozzle, which excellent spray characteristics are obtained at relatively low injection pressure, was developed. In this study, it was investigated about atomization of spray of the multi-hole atomization enhancement nozzle, and aimed to improve atomization characteristics and to obtain excellent spray characteristics. Effects of dimensions of the atomization enhancement nozzle, such as hole diameter and geometric shapes of nozzle hole, on atomization characteristics were investigated. As a result, it was cleared that in case of the multi-hole nozzle with hole number of N = 4, breakup length becomes short and spray angle becomes large about two times compared with the actual single hole nozzle. Atomization characteristics of continuous injection and intermittent injection were improved considerably by using the multi-hole nozzle with round inlet shape of nozzle hole and the multi-hole nozzle of hole number of N= 4 at high-ambient pi essure conditions for actual Diesel engine.
