CFD aided development of a SI-DI engine

Gasoline Direct Injection (GDI) appears to be the most relevant way to impr ove fuel efficiency of SI engines. But today, GDI is essentially regarded a s a suitable technology for relatively high displacement engines, and the l iterature shows that the R&D effort on GDI engines is generally made for bo res larger than 80 mm. For small bore engines (bore below 75 mm), locating an injector in already congested cylinder heads, with ultra lean stratified combustion capability while maintaining high engine specific power and pro per cylinder head cooling is a real challenge. For such an engine, IFP is d eveloping a 3-valve per cylinder engine (NSDI-3), based on a "narrow spacin g" concept, with a spark-plug-close-to-the-injector design and a suitable p iston to confine the gasoline spray within the vicinity of the ignition loc ation. This paper describes the contribution of 3D modeling to the developm ent of this engine, from the initial work during the design of the prototyp e combustion chamber, to the development and tuning of the prototype engine on the test bench.