The air flow in the same direction as the axis of the fan blade, such as the electric fan and the fan outside the air conditioner, is the axial flow fan. It is called "axial flow" because the gas flows parallel to the fan shaft. Axial flow fans are usually used in situations with high flow requirements and low pressure requirements. The axial flow fan is fixed and moves the air. Axial flow fan is mainly composed of fan impeller and casing, with simple structure but very high data requirements.