NUMERICAL STUDY OF THE EFFECT OF WALL INJECTION ON THE CAVITATION PHENOMENON IN DIESEL INJECTOR

Cavitation has an important effect on the performance of diesel injectors. It influences the nature of the fuel spray and formation of emissions. In contrast, cavitation increases the hydraulic resistance of the nozzle, creates flow instability, produces noise, and erodes the nozzle wall. In the present study, the effect of wall injection on the boundary layer separation in the cavitating and turbulent flow developing inside a diesel injector has been investigated numerically using two-phase mixture model. Simulations have been performed for different cavitation numbers, injection ratios and injection angles. Furthermore, the effects of various wall injection locations have been investigated and the results have been compared. The results indicated that for a particular injection angle, the highest discharge coefficient and the lowest number of cavitation bubbles were observed at a specific range of cavitation numbers. Also, with the injection from the orifice wall, the critical cavitation number diminishes, and only for a small interval of cavitation numbers, the discharge coefficient becomes a function of pressure difference between the two ends of injector. The idea of the current work could be a starting point for application of wall injection in injectors in order to increase the discharge coefficient, and, at the same time, to decrease the undesired effects of the cavitation phenomenon.