Abstract: An axial flow fan includes a first rotor having first blades and a second rotor having second blades. The first rotor is axially connected to the second rotor, and both of the first rotor and the second rotor are received in a first stator which has third blades extending from radially inward from an inner periphery thereof. A second stator is connected to the first stator and has fourth blades extending radially inward from an inner periphery thereof.

Abstract: An axial flow fan includes a first rotor having first blades and a second rotor having second blades. The first rotor is axially connected to the second rotor, and both of the first rotor and the second rotor are received in a first stator which has third blades extending from radially inward from an inner periphery thereof. A second stator is connected to the first stator and has fourth blades extending radially inward from an inner periphery thereof.

Abstract: The present invention provides an axial flow fan structure having an optimal airflow rate and pressure head. The axial flow fan structure includes a rotor provided with a plurality of fan blades which are overlapped with each other. In such a manner, variations of the chord angle, the air inlet angle, and the air outlet angle of the fan blade together with adjustment of the span of the fan blades co-operate with rotation of the fan blade to produce an optimal airflow rate and pressure head. In addition, the fan blades of the rotor may co-operate with a set of stator guide vanes, thereby further increase the pressure head of the airflow, while the airflow having a high flow rate and high pressurization is guided to a predetermined direction more efficiently.