A piston of a direct injection type diesel engine has a re-entrant type cavity, and a fuel injection nozzle with multiple nozzle holes is arranged on the center line thereof. The cavity has a lip portion, which is the portion thereof having the smallest diameter, positioned below a piston crown surface and a pocket portion formed above the lip portion. The pocket portion is positioned at a height to which a pilot injection injected prior to the top dead center under engine idling is directed, and the position of a wall surface is so set that a leading part of the injection spray does not collide strongly therewith. The fuel from the pilot injection temporarily stays in the pocket portion and moves into the cavity by means of a subsequent squish flow. Accordingly, an increase in unburned hydrocarbons is suppressed.

The present invention is a fuel injection method for a compression-ignition internal-combustion engine running in single-fuel or multi-fuel mode. The engine has at least a cylinder (10), a piston (16) sliding in the cylinder, a combustion chamber (34) comprising two mixing zones (Z1, Z2) which are defined on one side by upper face of the piston comprising a projection extending in the direction of the cylinder head and located in a center of a concave bowl (48), a cylinder head (12) carrying fuel injection (30) projects liquid fuel (Fuel1) in at least two fuel jet sheets (36, 38) with different sheet angles (A1, A2), and intake (24, 26, 28) for an oxidizer and burnt gas exhaust (18, 20, 22).The method, in a single-fuel mode, injects liquid fuel (Fuel1) into lower zone (Z1) and/or upper zone (Z2) of the combustion chamber and, in a multi-fuel mode, provides in the chamber mixing of an oxidizer with another fuel (Fuel2) and of injection of liquid fuel (Fuel1) into lower zone (Z1) or both zones (Z1, Z2) of the combustion chamber.

The present invention relates to a compression-ignition direct-injection internal-combustion engine comprising at least a cylinder (10), a cylinder head (12) carrying fuel injection means (14) projecting the fuel in at least two fuel jet sheets (36, 38) with different sheet angles (A1, A2), a piston (16) sliding in this cylinder, a combustion chamber (34) delimited on one side by upper face (44) of the piston comprising a teat (48) extending in the direction of the cylinder head and arranged in the centre of a concave bowl (46) with at least two mixing zones (Z1, Z2), and piston cooling means (76) housed in the material of the piston.

According to the invention, the cooling means comprise at least one circumferential gallery (78, 82) concentric to piston bowl (46) and arranged opposite at least one mixing zone (Z1, Z2).

A piston for Diesel engines having a combustion chamber with an optimized design to improve engine performances and to reduce engine emission.

The combustion chamber is provided by a specific profile and, in particular, by its central region with double inclination and by the tapered lateral step. This particular geometry of the combustion chamber aims to improve smoke formation and its oxidation, emissions at the engine outlet, thermal efficiency and carbon dioxide emissions.

Since the main characteristics of the combustion chamber can be parameterized, this combustion chamber can be applied to different types of diesel engines with any displacement, bore/stroke ratio, rotation speed and application.