Effectiveness of blade forward sweep in a small industrial tube-axial fan

Forward swept blades in low-speed axial fan rotors allow for appreciable gain in the stall margin and a small percentage gain in the maximum fan efficiency if the rotor blade circulation increases from the hub to tip. However, a reduction of the fan pressure at the design point counteracts these advantages. The paper investigates the effectiveness for small tube-axial fans of a design method suggested to increase the performance of an existing arbitrary vortex design by introducing the span-wise uniform distribution of blade forward sweep. The following three rotors for a 315-mm tube-axial fan have been tested: unswept, forward swept, and forward swept with additional sweep at the blade tip. Experimental data prove the effectiveness of the design method for these small fans.