Piston assembly and dynamic sealing assembly for underwater engine

The invention belongs to the technical field of special engine sealing devices, and particularly relates to a dynamic sealing assembly. The invention provides a dynamic sealing assembly. Sealing lips of a first auxiliary sealing ring and a second auxiliary sealing ring, a U-shaped dynamic sealing ring of a first main sealing ring and a dynamic sealing ring of a second main sealing ring are independently made of filling type polytetrafluoroethylene composite materials. The filled polytetrafluoroethylene composite material is prepared from the following components in parts by mass: 60 to 95 parts of polytetrafluoroethylene, 1 to 20 parts of macromolecular organic filler, 2 to 15 parts of carbon fiber and 0.1 to 5 parts of nano zirconium oxide, the macromolecular organic filler comprises polybenzoate or polyether-ether-ketone. The dynamic sealing assembly provided by the invention adopts a filling type polytetrafluoroethylene composite material as a sealing material of the sealing assembly, has good corrosion re