1, the motor pole number is too high, the motor spindle speed is slow, the air volume is small; 

2, the Blade Angle is small, the air volume is small; 

3, the Axial Flow Fan impeller craft is unreasonable, the aerodynamics is not fully utilized; 

4, the axial flow fan lacks the item to burn out, 

sometimes can turn, but it's slow, it's weak. The blades of the axial-flow fan are similar to airplane wings. However, the latter acts to support the weight of the airplane wing upward, and the fixed position of the axial fan moves the air. The Cross section of an axial fan is usually the wing profile. The blade may be in a fixed position or may rotate about its longitudinal axis. The blade-to-air or blade spacing angle can be either non-adjustable or adjustable. Changing the Blade Angle or pitch is one of the main advantages of axial flow fans. The smaller Blade Pitch Angle produces lower flow rate, while increasing blade pitch leads to higher flow rate.

http://www.dxymotors.com