Piston positioned for reciprocal movement in a combustion engine cylinder

A piston (3) arranged for reciprocal movement in a combustion engine cylinder (2) between a bottom dead center position and a top dead center position, said piston including a piston crown (16) comprising an upper surface facing a combustion chamber (7), said piston crown containing a piston bowl formed by an outwardly opening cavity, said piston bowl comprising an outwardly flared outer bowl section (20) having a concave curvilinear shape in cross section, at least one intake port (10, 12) arranged to provide the combustion chamber with intake air, an injector (13) arranged to inject fuel into the combustion chamber from a position adjacent a geometrical centre (15) of said combustion chamber and having an impingement area of a progressing flame plume in said outer bowl section, and where substantially half way between said impingement areas and in a plane substantially perpendicular to said reciprocal movement are arranged protrusions (70) protruding into the combustion chamber and having a smooth form adapted for preserving kinetic energy in a flame plume and where each of said protrusions (70) has a shape of a longitudinal ridge that extends only in the outer bowl area in a plane substantially parallel to or close to being parallel to said reciprocal movement, and where said ridge comprising a left side flank (80), a top section (81) and a right side flank (82) when seen in a plane perpendicular to said reciprocal movement, and where a transition section (83) is arranged between each of said side flanks and the top section, characterized in that said transition section (83) comprising a deflection edge (71) in order to minimize flow losses.