Self-Excited Instability of Closed-Type Swirl Injector with Varying Conditions

Abstract

The dynamic characteristic of an injector is important for improving engine characteristics and preventing instability. In this study, the experiments on the unstable flow of a closed-type swirl injector were conducted, and the dynamic characteristic analysis of the relationship between internal and external flows was discussed. Consequently, it was found that the unstable characteristics of internal and external flows were similar. Main geometric parameters affecting the injector self-excited instability were also investigated. The fluctuating amplitude was mainly related to the momentum of the flow. On the other hand, the instability frequency was related to the axial velocity inside the swirl injector. Experiments with external pulsation were carried out to investigate the effect of the instability frequency in real environments. It was observed that the mean breakup length reduced by 25%, and the fluctuation amplitude of the spray angle increased more than twice compared with the out of tuned case. The results of this study can be an inspiration to engine design, considering the dynamic characteristics of an injector.