短语词组短语piston type air compressor 活塞式空压机Reciprocating piston minitype air compressor 微型往复活塞空气压缩机free piston air compressor 自由活塞空气压缩机air compressor piston ring 空气压缩机活塞环air compressor piston 空气压缩机活塞 返回 piston air compressor