Comparative studies have been carried out on two axial flow fan rotors at their design
flow rate in order to investigate the combined effects of controlled vortex design
and circumferential forward skew on blade aerodynamics. The studies were based on
Computational Fluid Dynamics, with composition and application of structured hexahedral
grids taking up the challenge of the relatively complicated blade geometries due to
skew and sweep. The computations indicated that the forward-skewed blade tip modifies
the inlet flow field, leading to the rearrangement of spanwise blade load distribution,
increase of losses along the dominant part of span, and converting the original non-free
vortex spanwise blade circulation distribution toward a free-vortex flow pattern.
The radial outward flow on the suction side, being especially significant for non-free
vortex rotors, was found to be effectively moderated by forward skew, together with
the losses associated. It has been concluded that forward skew is especially recommended
for non-free vortex rotors for retardation of tip stalling.