A piston for a direct injection engine is provided, the piston having a bowl at an upper end, the bowl forming a portion of a combustion chamber. The bowl includes an inner surface that defines a volume configured to receive a fuel-air mixture, the inner surface of the bowl including a generally concave portion including a flat bottom surrounding a central protruding dome. The relatively flat bottom portion is bounded by two radial concave surface portions which are disposed below two convex separation features for the injected fuel spray. Such surface geometries may reduce soot and improve fuel-air mixing.
Rainer J. Rothbauer; Charles E. Roberts Jr.; Chad H. Stovell