Design for high efficiency of low-pressure axial fans: use of blade sweep and vortex distribution

Rotor-only low-pressure axial fans with small hub-to-tip diameter ratio (HTR in short) are widely used in many branches of industry, especially for cooling and ventilation purposes. As energy- related products that account for a significant proportion of the consumption of natural resources and energy, optimization of their aerodynamic performance for high efficiency is important to reduce environmental impact. Differently from low-pressure axial fans with medium to high HTR, extensive regions of backflow near the hub are often present downstream of fans with small HTR.
In studies of low-pressure axial fans, Computational Fluid Dynamics (CFD) simulations have been frequently employed to analyze in detail the aerodynamic performance and the flow fields inside these machines. For optimization, according to investigations on axial fans with medium to high HTR, sweep, dihedral and skew of the blades stacking line as well as different vortex distribution designs form important methods. However, for fans with small HTR, only few studies have been reported in the scientific literature on appropriate CFD simulation strategy, three-dimensional stacking and vortex distribution design method.
The objective of this thesis is to investigate the effects of sweep, dihedral and skew on the aero- dynamic performance of low-pressure axial fans with small HTR and develop an optimal vortex distribution design method for high efficiency of such fans. CFD simulations are extensively used in these investigations.