Numerical Analysis on Aerodynamic Performance of Counter-rotating Wind Turbine through Rear Rotor Configuration

Abstract

Numerical analysis was conducted on the aerodynamic performance and the flow characteristics around the counter-rotating wind turbine or CRWT blade through rear rotor configuration using various rotor diameter ratios and distance ratios to the turbine blade through a CFD (Computational Fluid Dynamics) simulation. CFD simulation showed the normalized power coefficients of the front rotor, rear rotor, and combined rotor (CRWT) to the single rotor with a strong influence of the rear rotor configuration with the addition of tip speed ratio (TSR). A larger average normalized power coefficient takes place at D1/D2=1.0 with L/D1=0.75 by 1.221. It is about 22.1% increased to the SRWT for the given TSR range. Axial velocity contours and resultant velocity vectors around the CRWT blade with a diameter ratio of D1/D2 > 1.0 and a closer rotor distance provide a stronger bound vortex and strong separation around the rear hub blade with a tendency to increase from the hub to the tip blade at low TSR. The higher the TSR, the movement of tip vortex moves closer to the rear tip blade which has the effect of increasing the leakage flow in the area of D1/D2 < 1.0.