Experimental Characterization of High-Pressure Impinging Sprays for CFD Modeling of GDI Engines

Today, Direct-Injection systems are widely used on Spark-Ignition engines in combination with turbo-charging to reduce the fuel-consumption and the knock risks. In particular, the spread of Gasoline Direct Injection (GDI) systems is mainly related to the use of new generations of multi-hole, high-pressure injectors whose characteristics are quite different with respect to the hollow-cone, low-pressure injectors adopted in the last decade. This paper presents the evidences of an experimental campaign conducted on the spray produced by a GDI six-holes injector into a constant volume vessel with optical access. The vessel was filled by air at atmospheric pressure. Different operating conditions were considered for an injection pressure ranging from 3 to 20 MPa. For each operating condition, spray images were acquired by a CCD camera and then post processed to evaluate the spray penetration and cone angles. A flat plate was placed inside the vessel to investigate the spray-wall impingement and liquid-film evolution. The experimental database was used to obtain a first evaluation about a CFD methodology defined to simulate the GDI spray behavior. This methodology was based on a classic Eulerian-Lagrangian approach and it was implemented into the Lib-ICE code, developed into the OpenFOAM platform. In particular, specific sub-models were implemented to correctly reproduce the fuel atomization and the droplet-wall interaction.