Analysis and visualisation of flow around blades of axial fans for large capacity open-type motors

A study of the airflow around blades of axial fans for large capacity open type motors is presented. In these motors, air for cooling is blown onto stator windings and rotor bars by means of axial fans placed beside the laminated iron core. The paths from the intake opening to the axial fans and from the laminate iron core to the exhaust opening twist tightly in order to reduce noise. The ventilation resistance of axial fans for motors is much greater than that of common fans for creating draughts. The operating flow rate is much less than for fans without ventilation resistance. Numerical flow analysis was performed on the flow around the blade at this operating point. It was confirmed that there was a large flow segregation where air did not flow along surfaces on the negative pressure side of blades. This was also observed in a flow visualisation experiment.