High Pressure Diesel-Like Injections for GDI Engine: Experimental and Numerical Approach

Multihole injectors, working like diesel valve coverage orifice (VCO) or mini-sac nozzle, seem to be the future trend for GDI (Gasoline Direct Injection) applications. The GDI approach through this injector type is very similar to diesel one. A diesel-like electronically controlled Common Rail injection apparatus has been used for pressure up to 100 MPa. An axially disposed single hole 0.18 mm in diameter and 1.0 mm in length injected a gasoline-like fluid in an optically accessible vessel filled with inert gas (N2) and controlled in pressure up to 1.2 MPa. The jets emerging from the injector hole have been lightened by a pulsed laser sheet at different instant from the start of injection. The images were collected by a CCD camera, synchronized with the light, and processed by professional software to extract the significant parameters of the evolving spray (penetration, cone angle, velocity). Some results of a work in progress aiming to select and validate proper models for the various stages of spray development are also discussed. Four different models have been compared, to evaluate the one that better represents the characteristics of the generated spray. The final goal of the research activity is to set up the KIVA 3V code for its extensive use in the design and development of GDI engines.