The cross-flow fan, also known as the cross-flow fan, was first proposed by the French engineer Mortier in 1892. The impeller is multi-blade, long cylindrical, and has a forward multi-airfoil blade. Its structure is shown in the figure below. When the impeller rotates, the air flow enters the cascade from the open part of the impeller, passes through the inside of the impeller, and drains into the volute from the other side of the cascade to form the working air flow. The flow of air in the impeller is very complicated, the flow velocity field is unstable, and there is a vortex in the impeller, the center is located near the cochlear tongue. The existence of the vortex makes the output end of the impeller produce circulation flow, outside the vortex, the flow line in the impeller is circular. Therefore, the flow rate of each point on the outer circumference of the impeller is inconsistent, the closer to the vortex center, the greater the speed, the closer to the volute, the smaller the speed. The airflow speed and pressure at the outlet of the fan are not uniform, so the flow coefficient and pressure coefficient of the fan are average values. The position of the vortex has a great influence on the performance of the cross-flow fan. The center of the vortex is close to the inner circle of the impeller and close to the spiral tongue, and the performance of the fan is better. If the vortex center is far away from the vortex tongue, the circulating flow area increases, the fan efficiency decreases, and the flow instability degree increases.

The cross-flow fan is mainly composed of an impeller, an air duct and a motor, and the impeller material is generally aluminum alloy or engineering plastic. The aluminum alloy impeller has high strength, light weight, high temperature resistance, and can maintain long-term stable operation without deformation; The plastic impeller is made of mold injection molding and then welded by ultrasonic wave. It is generally used for occasions with low speed and large diameter.

The air duct is generally formed by sheet metal stamping, and can also be cast in plastic or aluminum alloy. The casing adopts streamlined design, which can effectively reduce the loss of air flow and greatly improve the working efficiency of the fan.

The motor is the power part of the cross-flow fan, which can be powered by AC or DC. Ac power supply is mainly covered pole motor and capacitor start motor, DC power supply is DC brushless motor. MH motor and impeller are generally flexible installation, fixed on the air duct.