Cross flow fan was first proposed by French engineer Mortier in 1892. The impeller is multi blade, long cylindrical and has forward multi wing blades.

When the impeller rotates, the air flow enters the cascade from the open part of the impeller, passes through the interior of the impeller, and is discharged into the volute from the cascade on the other side to form the working air flow. The flow of air in the impeller is very complex, the air velocity field is unstable, and there is also a vortex in the impeller, whose center is near the cochlear tongue. The existence of vortex makes the output end of the impeller produce circulating flow. Outside the vortex, the air flow streamline in the impeller is in a circular arc shape. Therefore, the flow velocity at each point on the outer circumference of the impeller is not uniform. The closer to the vortex center, the faster the velocity, and the closer to the vortex shell, the smaller the velocity.

The air velocity and pressure at the fan outlet are not uniform, so the flow coefficient and pressure coefficient of the fan are average. The position of the vortex has a great influence on the performance of the cross flow cooling fan. The center of vortex is close to the inner circumference of impeller and the volute tongue, so the performance of fan is better. When the center of vortex is far away from the vortex tongue, the area of circulating flow increases, the fan efficiency decreases and the flow instability increases.

Cross flow fan is mainly composed of impeller, housing and motor.

The impeller material is generally aluminum alloy or engineering plastic. Aluminum alloy impeller has high strength, light weight and high temperature resistance, and can maintain long-term and stable operation without deformation; Plastic impellers are injection molded by molds and welded by ultrasonic waves. It is generally used in low speed occasions with large diameter.

Generally, the housing is stamped and formed by sheet metal, and can also be cast by plastic or aluminum alloy. The streamlined design of the casing can effectively reduce the loss of airflow and greatly improve the working efficiency of the fan.

The motor is the power part of the cross flow fan, which can supply AC power or DC power. AC cross flow fan power supply mainly includes shaded pole motor and capacitor starter motor, while DC cross flow fan power supply is DC brushless motor. Generally, the driving motor is flexibly installed with the impeller and fixed on the housing.

Advantages and disadvantages of cross flow fan:

a. The axial length is not limited, and the length of the impeller can be arbitrarily selected according to different use needs;

b. The airflow flows through the impeller and is affected by the secondary force of the blade, so the airflow can reach a long distance;

c. No turbulence and uniform air outlet;

d. Because the air flow is forced to turn in the impeller, the pressure head loss is large and the efficiency is low.