positive ventilation的用法和樣例：
例句
- What's the requirement for the forced ventilation system for crankcase?
發(fā)動(dòng)機曲軸箱強制通風(fēng)的要求？ - All automobile engines now built are equipped with the positive-crankcase ventilation system of crankcase emission control.
所有現代制造的汽車(chē)發(fā)動(dòng)機，都需要裝備控制曲軸箱有害污染的曲軸箱強制通風(fēng)系統。
