According to the method, fuel is injected into a combustion chamber of an internal-combustion engine via an atomizer (10) provided with a nozzle (11) having an internal seat (13) and a sealing seat (21); the atomizer is moreover provided with a valve needle (12) having a head (20) designed to couple to the sealing seat (21) and a stem (41), which engages the internal seat (13); the stem (41) and the nozzle (11) define a passage (16) having an annular chamber (43), which axially ends at the sealing seat (21); the stem (41) has an intermediate portion (45) coupled in an axially sliding way in the internal seat (13) and defining a plurality of channels (67), the outlets (72) of which are arranged at the annular chamber (43); the sealing seat (21) and the head (20) of the valve needle (12) define a outflow area (14), which is annular and has a width that increases as the opening stroke of the valve needle (12) progresses; the fuel is injected in such a way as to have a non-uniform velocity modulus at the outflow area (14), as the position in the circumferential direction varies, at least in a reference operating condition of the engine.