Numerical investigation of the effect of blade distortion laws on the corner flow separation of the axial-flow fan

Abstract

To study the effect on performance of different blade distortion laws of axial flow fans, the radial distributions of blade stagger angle were fit as Bézier curves, and five distribution laws were established. Three-dimensional numerical simulations were carried out for the fan schemes. The results show that distortion near the blade root can effectively restrain the corner separation vortex from climbing along the blade suction surface, so that the low-energy fluid accumulates in the corner region. Tip distortion rises the pressure difference between the pressure and the suction surface, and the turbulence intensity of the tip leakage is increased. Root distortion inhibits the CV diffusion, resulting the decay of tip leakage vortex, thereby improving the stall margin. Relative to a uniform distortion blade, the blade-root distortion scheme increases the radial load of the blade, while the tip distortion scheme results in a decrease of the blade load coefficient. The maximum load position of the end-zone distorted blade moves to the root area, while the maximum load position of the middle distorted blade shifts to the tip area. The end-zone distortion improves the efficiency and total pressure of the fan without changing the efficient working range, and is considered to be the optimal scheme. The maximum pressure coefficient of the end-zone distortion scheme is increased by 4.97% and the maximum efficiency is increased by 1.28%.