Reciprocating internal-combustion engine with direct fuel injection by means of an injector arranged on the intake side

A method of operating a reciprocating internal-combustion engine, having at least two gas intake ports (3) with gas intake valves (6), at least one gas exhaust port (4) with a gas exhaust valve (7) and at least one ignition device (14) per cylinder (1), and having a combustion chamber (1.1) formed by the cylinder cover (2.1) and the crown (11.1) of the piston (11), which is guided in the cylinder (1) in a reciprocating manner, into which combustion chamber the gas intake ports open at a flat angle of less than 45 degrees, measured in relation to the cylinder-head plane (2.1), wherein the piston crown (11.1) on the one hand and the cylinder cover (2.1) on the other hand are substantially roof-shaped in vertical section, wherein in each case one of the roof surfaces is associated with the gas intake valves (6) and the other roof surface is associated with the gas exhaust valve (7), and the orientation of the roof surfaces of the cylinder cover (2.1) corresponds to the orientation of the roof surfaces of the piston crown (11.1), and having a fuel injection nozzle (8) opening into the cylinder (1) near the inlet region of the gas intake ports (3) between the gas intake valves (6), wherein, measured in relation to the cylinder axis (5), the angle of the jet axis (9) of the fuel injection nozzle (8) is greater than the angle of the gas intake ports, and having an ignition device (14) arranged in the cylinder cover (2.1) close to the cylinder axis (5), and having a trough-shaped recess (12) which is provided in the piston crown (11.1) and is bounded by a trough base (12.1) and side walls (16) and which intersects the roof ridge (11.2) on the piston crown and extends over the region of both roof surfaces, the trough base (12.1) slopes towards the fuel injection nozzle (8) and ending in a wall zone (12.2) extending steeply upwards on its side facing the fuel injection nozzle (8), wherein the transition region (15) between the trough base (12.1) and the side walls (16) has a substantially barrel-shaped contour in plan view, which first widens on both sides from the gas exhaust side (4) and then narrows again towards the gas intake side, one end of which is formed by the wall zone (12.2) extending steeply upwards, so that in the vicinity of the piston crown, the tumble flow is first expanded slightly transversely to the flow direction, thereby slowed down slightly, and then consolidated again, thereby accelerated, immediately before the transition to the wall zone extending steeply upwards, which imparts turbulence to the tumble flow.