Comparative study of the performances of twisted two-bladed and three-bladed airfoil shaped H-Darrieus turbines by computational and experimental methods

Abstract

The vertical axis H-Darrieus turbines are simple in construction, self-starting, omni-directional, and self-regulating at all wind speeds. A comparative study of the performances of twisted two-bladed and three-bladed airfoil shaped H-Darrieus turbines was made. The models of the turbines were designed, fabricated, and tested in a subsonic wind tunnel. The power coefficients (C p ) and torque coefficients (C t ) were evaluated for ten numbers of height-to-diameter (H/D) ratios. Both C p and C t of the two-bladed turbine were higher than the three-bladed turbine. The maximum C p for the two-bladed turbine was 0.237 and that for the three-bladed turbine was 0.151. The performances of the turbines were also compared computationally through 2D steady-state CFD simulations using Fluent 6.2 software. The agreement between the computational and experimental C p was within ± 5.86%. The contour plots of static and dynamic pressures and velocity magnitudes were generated for chord Reynolds number of 8.5 × 10 4 . At any position on the blade, dynamic pressure, velocity and also the velocity gradient between the ends were higher for the two-bladed turbine than the three-bladed turbine.