Reduction of Spray Momentum for GDI High-Pressure Injectors - A Necessary Step to Accomplish Series Production of Super-Charged DI-Engines

The first part of the present paper describes the means by which the spray momentum can be decreased. The objective can be obtained either by injector-internal geometrical design changes, which very often lead to a highly non-uniform spray density/droplet distribution or by a new injector-external process, called the colliding jet (CJ) approach. The paper continues with a detailed description of the physics of the controlled secondary breakup process provided by the CJ-approach, which enables a very uniform density/droplet distribution on the downstream side of the collision zone as well as an approximately 40 % decrease in spray penetration depth. The knowledge of the physics of the CJ-approach enables the introduction of a new spray model in the 3-D numerical simulation code NCF-3D. The presence of a CJ-spray model within the NCF-3D code enables a comparison of the dynamic spray behavior from different atomizer layouts, designed to decrease the spray penetration, on a virtual, numerically simulated multi-cylinder engine as well as on a real physical engine test rig.

The paper concludes with a rating of the performances and risks produced by the different fuel injector atomizer approaches to decreasing the high rail-pressure spray penetration depth.