短語詞組短語piston ring type seal 漲圈式密封piston ring seal system 活塞環(huán)密封系統(tǒng)piston o -ring seal 柱塞O型密封圈Piston seal ring 活塞封dummy piston seal ring 平衡活塞汽封triple seal piston ring 三重密封活塞環(huán) 返回 piston ring seal