风机是依托输入的机械能进步气体压力并排送气体的机械，它是一种从动的流体机械。
A fan is a type of driven fluid machinery that relies on input mechanical energy to increase gas pressure and discharge gas.
风机按运用材质分类能够分好几种，如铁壳风机（一般风机）、玻璃钢风机、塑料风机、铝风机、不锈钢风机等等
Fans can be classified into several types based on the material used, such as iron shell fans (general fans), fiberglass fans, plastic fans, aluminum fans, stainless steel fans, and so on
风机分类能够按气体活动的方向，分为离心式、轴流式、斜流式（混流式）和横流式等类型。
Fan classification can be divided into centrifugal, axial, oblique (mixed flow), and cross flow types according to the direction of gas activity.
(1)离心风机。气流轴向进入风机的叶轮后主要沿径向活动。这类风机依据离心作用的原理制成，产品包含离心通风机、离心鼓风机和离心压缩机。
(1) Centrifugal fan. After the airflow enters the impeller of the fan axially, it mainly moves radially. This type of fan is made based on the principle of centrifugal action, and its products include centrifugal fans, centrifugal blowers, and centrifugal compressors.
(2)轴流风机。气流轴向进入风机的叶轮，近似地在圆柱形表面上沿轴线方向活动。这类风机包含轴流转风机、轴流鼓风机和轴流压缩机。
(2) Axial flow fan. The airflow enters the impeller of the fan axially and moves approximately along the axis direction on a cylindrical surface. This type of fan includes axial flow fans, axial flow blowers, and axial flow compressors.
(3)反转风机。使用转子旋转改变气室容积来进行工作。常见的种类有罗茨鼓风机、反转压缩机。
(3) Reverse the fan. Use the rotor rotation to change the volume of the air chamber for operation. Common types include Roots blowers and reverse compressors.