求翻译：4、风叶结构。开发初期基本采用后向风叶，只有少数采用前向风叶，进入九十年代开始采用涡轮喷射风叶。前向风叶的风景、风压、油脂分离度均达到较好水平，而后向风叶风压和油脂分离度两项指标偏低，使用效果不佳。涡轮喷射风叶是引进国外的新结构，各项使用性能均较好。目前深箱型吸油烟机均采用千叶型风叶。是什么意思？

4, fan structure. After the initial development of the basic use of the fan, fan only a few uses forward into the nineties began to use turbo fan jet. Prior to the blades of the landscape, air pressure, oil separation reached a good level, and then to fan pressure and low oil separation two indicato

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4th, wind leaf structure.After the development initial period uses the windward leaf basically before, only then minority uses the windward leaf, enters for the 90's to start to use the turbine wheel spraying wind leaf.The first windward leaf's scenery, the wind pressure, the fat degree of dissociat

4, blade structure. Development early adoption to the blades after, only a forward wind blade, introduced in 90 's turbine jet-blades. First wind of landscape, wind pressure and oil separation has reached a good level, and then to the blades of wind pressure and oil separation of two low, is not opt

4, fan structure. After the initial development of the basic use of the fan, fan only a few uses forward into the nineties began to use turbo fan jet. Prior to the blades of the landscape, air pressure, oil separation reached a good level, and then to fan pressure and low oil separation two indicato