Cavitation and Hydraulic Flip in the Outward-Opening GDi Injector Valve-Group

Experimental (optical imaging) and CFD investigations of the cavitating flow in a transparent large-scale model of a GDi outward-opening injector, with a swirler-type valve-group, has been performed. The objective is to elucidate the flow structure within the valve group and assess a Reynolds-Averaged Navier-Stokes (RANS) multi-fluid simulation method.

The optical imaging data show evidence of cavitation inception in the valve-group swirler-channels-caused by the rapid flow acceleration-and multiple cavitations within the conical nozzle region.

The comparison of simulations with data shows that the CFD method reproduces the fluid dynamics of the valve-group with good qualitative agreement with the imaging data (with respect to the cavitation inception and geometry) and excellent quantitative agreement of the valve-group pressure drop-flow rate characteristic. In addition, the simulations reveal that the apparent cavitation in the conical nozzle region involves a “partial hydraulic flip” phenomena and entrainment of the ambient air.