Patent ID: 8770168

Claim:
A direct injection diesel engine including: a cylinder block defining at least one cylinder which is closed by a cylinder head and reciprocally receives a respective piston, the piston defining a combustion chamber comprising: a recess formed in a piston crown, the recess being rotationally symmetrical about an axis of the piston in axial cross-section and defined by a base and a side wall, a substantially conical or frusto-conical projection upstanding from the base, the recess including a lower toroidal portion furthest from the piston crown and an upper portion closest to the piston crown whose diameter progressively increases towards the piston crown, the upper and lower portions being separated by an annular lip of arcuate shape in axial cross-section extending into the recess, an included angle of the conical or frusto-conical projection between 104° and 108°, the maximum depth of the recess from the base to a plane of the piston crown between 13 and 22% of a diameter of the piston, the substantially conical or frusto-conical projection merging with the base along a circular line whose diameter is between 38 and 44% of the diameter of the piston, a diameter of the annular lip between 54 and 59% of the diameter of the piston, a line of minimum diameter of the annular lip situated at a distance of between 5 and 10% of the diameter of the piston from the plane of the piston crown, and a diameter of the upper portion of the recess increasing from 54 to 59% of the diameter of the piston at the line of minimum diameter of the annular lip to between 72 and 76% of the diameter of the piston at the line, the side wall of the recess intersecting the plane of the piston crown, wherein the cylinder head includes a fuel injector which is situated substantially on the cylinder axis and includes a plurality of fuel injection orifices, wherein the cylinder is configured to communicate with two inlet valves and two exhaust valves in the cylinder head, wherein the inlet valves are arranged to induce swirl of the inflowing air in the cylinder substantially about the cylinder axis, wherein the fuel injection orifices are arranged so that the fuel jets through them extend at an angle which diverges from the surface of the projection by 15 to 19°, and wherein the fuel jets impinge firstly on the arcuate side wall of the lower portion of the recess.