A LARGE TURBOCHARGED TWO-STROKE UNIFLOW CROSSHEAD INTERNAL COMBUSTION ENGINE

Described is a large turbocharged two-stroke uniflow crosshead internal combustion engine, which has at least one mode of operation in which the main fuel is a low flash point fuel, such as ammonia, ethane, LPG or DME, which main fuel is injected at high pressure according to the diesel principle, the engine comprising at least one cylinder with a cylinder liner (1), a reciprocating piston (10) therein and cylinder cover (22) covering the cylinder, a combustion chamber formed inside the cylinder between the reciprocating piston (10) and the cylinder cover (22), a low flash point fuel system (30) configured for supplying pressurized fuel to at least one fuel valve (50) that is arranged in the cylinder cover (22) or in the cylinder liner (10), and a purging system for evacuation of the low flash point fuel. The engine is peculiar in that said purging system comprises means (42, 43, 44, 45) for depressurization and drainage of liquid fuel from the low flash point fuel system to a tank (57) in a first evacuation step and a vacuum pump system (71) for lowering the pressure and pumping out the remaining fuel from the low flash point fuel system to a tank (61, 57) in a second evacuation step. Hence, the low flash point fuel, such as ammonia, can be evacuated from the fuel system in a safe and economic way, where the low flash point fuel is collected in a tank for reuse as fuel and a costly and complicated handling of a mixture of nitrogen and fuel is avoided, as no inert gas, such as nitrogen is used for purging. Furthermore, the vacuum pump system pumps pure fuel gas with no contamination from a purging gas, and accordingly, said fuel gas can still be used as a fuel, if requested.