DESIGN OF FORWARD-INCLINED BLADES FOR A 0.5 HUB-TO-TIP RATIO TUBE-AXIAL FAN

The paper deals with the design of forward-inclined blades, where “forward-inclination” is intended as the design-dependent amount of forward sweep to be incorporated in non-free-vortex blades to restore a quasi-2D flow behaviour within the rotor passages. The aim of the work is to assess the effectiveness of this design modification in a 0.5 hub-to-tip ratio fan with radially stacked blades that induce a roughly constant-swirl velocity at the rotor exit. To this end, the original blade has been modified by incorporation of a forward sweep amount that translates into a forward-inclined design, defined in accordance with a method suggested by the authors. The forward-inclined design demonstrated experimentally to improve pressure rise and efficiency of the original fan in the whole operation range with ca 10% gain at design operation.