Direct injection diesel engines

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.