Definition of a CFD Multiphase Simulation Strategy to Allow a First Evaluation of the Cavitation Erosion Risk Inside High-Pressure Injector

Abstract

Diesel engine performance is strictly correlated to the fluid dynamic characteristics of the injection system. Actual Diesel engines employ injector characterized by injection pressure till 200MPa that, associated to micro-orifice design, result in critical flow conditions inside injector holes.One of the most remarkable consequence of the critical flow conditions inside injector holes is the cavitation phenomenon. The cavitation inside the injector tip and holes can be correlated to two main effects. The first one is on the spray shape and on the atomization process. The second one is on the physical erosion generated on the injector internal walls by the vapour bubble collapse.About the cavitation erosion risk, it is necessary to quantitatively predict the cavitation aggressiveness and the most probable location of cavitation erosion: they are complex problems that cannot be solved by the application of experimental techniques. For this reason, the application of fully transient CFD multiphase simulation (i.e. the needle motion is reproduced during the simulation) can be considered as a very useful approach to evaluate the multiphase flow behaviour inside real size injector holes.The present work addresses two main issues: numerical simulation of cavitating flows inside injector holes and an assessment of the cavitation erosion risk in terms of both 3D map and magnitude. All the analysis are performed by adopting a 3D-CFD multiphase simulation strategy validated against experimental data.