Experimental Investigation of Secondary Flows in a Low Hub-Tip Ratio Fan

The paper deals with an experimental investigation of the three-dimensional flow field at the exit of a low hub/tip ratio industrial axial fan. The relative flow was evaluated with fixed hot wire probes using the multisampling and phase-locked ensemble averaging techniques. Both mean flows and secondary flows are examined for different blade loading and stagger angles. The mean flows observed indicate a large separated flow region at the hub that is accentuated at the higher stagger angle. The secondary flows are particularly strong and affect the entire flow field. Their structure and location are also modified when stagger angle and blade loading are changed. The most complex situation is observed at the hub where a change in blade loading and stagger angle results in the interaction of the trailing vortex with the separated flow region, the passage vortex and midpassage region flow.