GDI Spray-Wall Interaction with Numerical Characterization: Wall Temperature Influence 2015-01-0917

The work analyses, from both an experimental and a numerical point of view, the impingement of a spray generated from a GDI injector on a hot solid wall. The temperature of the surface is identified as an important parameter affecting the outcome after impact. A gasoline spray issuing from a customized single-hole injector is characterized in a quiescent optically-accessible vessel as it impacts on an aluminum plate placed at 22.5 mm from the injector tip. Optical investigations are carried out at atmospheric back-pressure by a direct schlieren optical set-up using a LED as light source. A synchronized C-Mos high-speed camera captures cycle-resolved images of the evolving impact. The spatial and temporal evolution of the liquid and vapor phases are derived. They serve to define a data base to be used for the validation of a properly formulated 3D CFD model suitable to describe the impact of the fuel on the piston head in a real engine. The numerical simulations are effected in order to highlight the predictive capabilities of the model proposed by Kuhnke, not only with respect to the various hydro-dynamic regimes of splashing and deposition of impacting droplets, but also in consideration of the transient heat transfer between the wall and the droplets, that enhances evaporation. Three injection pressures are tested. Two values of the wall temperature are assumed, being above the Leidenfrost point for gasoline.