Method of injecting fuel into the combustion chamber of an internal-combustion engine running in single-fuel or multi-fuel mode

A method of fuel injection in a compression-ignition-internal combustion engine which includes an intake, at least one cylinder, each cylinder including a cylinder head, a piston sliding in the cylinder, a combustion chamber with an upper mixing zone and a lower mixing zone, the mixing zones being defined on one side by an upper face of the piston including a projection extending toward the cylinder head and located in a center of a concave bowl, at least one fuel injector located in the cylinder head which injects liquid fuel at least as an upper sheet having an upper sheet angle into the upper mixing zone and as a lower sheet having a lower sheet angle into the lower mixing zone, an intake for an oxidizer and a burnt gas exhaust, the method comprising:

• in a single fuel mode injecting the liquid fuel into at least one of the upper zone and the lower zone of the combustion chamber which is ignited by compression ignition;
• in a multi-fuel mode simultaneously feeding a gaseous fuel comprising one of (CNG), (LPG) and biogas through the intake into the combustion chamber to provide a mixture of an oxidizer and a second fuel and injecting the liquid fuel into the lower zone or into both the upper and lower zones of the combustion chamber and self-ignition of the liquid fuel ignites the gaseous fuel during the multi-fuel mode.