Comparison Study of a Vertical-Axis Spiral Rotor and a Conventional Savonius Rotor

A vertical-axis spiral rotor with two end plates and one middle plate was proposed for achieving a high wind energy transfer efficiency. Computational fluid dynamics (CFD) technology was adopted to evaluate the performance of the spiral rotor. Three-dimensional flow simulation was conducted by using Spalart-Allmaras one-equation turbulence model. Comparison of the spiral rotor with a conventional Savonius rotor was performed. Flow characteristics around the two rotors were analyzed to illustrate the correlation between flow and rotor performance. The study indicates that torque performance of the spiral rotor is more favorable during its whole rotation cycle. When maximum torque coefficient is generated, large pressure difference can be found between the convex and concave side of the blade. Oppositely, the minimum static coefficient is accompanied by indistinctive pressure difference and large-scale boundary layer separation zones.