draft fan的用法和樣例：
例句
- The fan at the window made a small whispering roar.
窗上的通風(fēng)機發(fā)出了耳語(yǔ)般輕微的嗡嗡聲。 - Formula of circulating coefficient actual value calculated according to fan actual performance and characteristic dimension is discussed.
探討了依據通風(fēng)機實(shí)際性能和特性尺寸計算環(huán)流系數實(shí)際值的公式。
