一、船舶推進裝置是輪機中最主要的部分，請簡述推進裝置的組成。（20 分）

⑵ The fresh water cooling system is a closed cooling system, in which the fresh water first passes the fresh water cooler, where it is cooled by sea water, and then is circulated through the cooling water jackets of the main engine by fresh water pump to cool cylinder liners, cylinder heads and exhaust valves.