短语词组短語blow -down valve 排氣閥;排汙閥;排放閥;排水閥sequencing blow -down valve 順序排汙閥surface blow -down valve 上排汙閥boiler blow down valve 鍋爐排汙閥BLOW DOWN VALVE BDV 排空閥bottom blow down valve 底部排汙閥BDV blow down valve 放泄閥;疏水閥 返回 blow down valve