Gas feeding system with shaft seal and cylinder for a reciprocating piston combustion engine, reciprocating piston combustion engine, and method for operating a reciprocating piston combustion engine

The invention relates to a gas supply system (1) for a reciprocating piston internal combustion engine, in particular a longitudinally scavenged two-stroke large diesel engine, wherein the gas supply system (1) comprises a gas inlet valve (2) with a gas inlet nozzle (3) which is designed such that it can be arranged in a cylinder wall (41) of a cylinder (4) of the reciprocating piston internal combustion engine in such a way that a fuel gas (5) provided as fuel can be supplied to a combustion chamber (42) of the cylinder (4) via the gas inlet nozzle (3) in the installed state of the gas supply system (1). According to the invention, the valve stem (61) is guided in a guide bore (91) of a shaft housing (9) and the guide bore (91) can be subjected to a hydraulic oil (10) under a sealing pressure (PA), which sealing pressure (PA) is preferably higher than a fuel gas pressure (BG) of the fuel gas (5) in the pressure space (22), so that penetration of the fuel gas (5) into the valve stem (61) can be substantially prevented. The invention further relates to a cylinder and a reciprocating piston internal combustion engine with a gas supply system (1) as well as a method for operating a reciprocating piston internal combustion engine.