Improving efficiency of Savonius wind turbine by means of an airfoil-shaped deflector
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(2020) 42:528
TECHNICAL PAPER
Improving efficiency of Savonius wind turbine by means of an airfoil‑shaped deflector Keyhan Layeghmand1 · Nima Ghiasi Tabari1 · Mehran Zarkesh1 Received: 1 March 2020 / Accepted: 3 September 2020 © The Brazilian Society of Mechanical Sciences and Engineering 2020
Abstract In the present study, a novel deflector system was proposed to improve the performance of a Savonius wind turbine through Computational Fluid Dynamics (CFD) simulation. For this purpose, an airfoil-shaped deflector was proposed and placed in front of the turbine to prevent the negative torque affecting the convex surface of the returning blade and also making it possible for deflecting the wind into the advancing blade. Different configurations of the proposed deflector system were considered numerically using the CFD solver. A three-dimensional incompressible unsteady Reynolds-averaged Navier–Stokes simulation in conjunction with the SST k − ω turbulence model was done and validated with the available experimental data. The predicted results indicated that the performance of the Savonius rotor is highly dependent on the position and angle of the deflector. Thus, there was an appropriate position and angle values to obtain the highest torque and power coefficients. It was concluded that using the favorable airfoil-shaped deflector significantly enhanced the static torque coefficient values in all angular ranges especially in the rotation angles between 0°–30° and 150°–180°. By properly covering the returning blade using the airfoil-shaped deflector, the static torque coefficient values increased up to two times higher than that generated by without deflector case. Keywords Wind turbine · Airfoil · Deflector · Savonius · Computational fluid dynamics (CFD) List of symbols θ Angle associated to the time step (°) ω Angular velocity of the rotor (rad/s) A Area swept by the turbine (m2) α Deflector angle (°) L Deflector distance (m) ρ Density of air (kg/m3) d Diameter of the blades (m) D Diameter of the turbine (m) y+ Dimensionless wall distance (-) µ Dynamic viscosity of air (kg/ms) H Height of the turbine (m) U∞ Incoming velocity (m/s) s Overlap (m) Pr Power (W) Cp Power coefficient (-) Technical Editor: Daniel Onofre de Almeida Cruz, D.Sc. * Nima Ghiasi Tabari [email protected] 1
Department of Mechanical Engineering, Dashtestan Branch, Islamic Azad University, Borazjan, Iran
P Pressure (Pa) Re Reynolds number (-) Cms Static torque coefficient (-) ∆t Time step (s) λ Tip Speed Ratio (TSR) (-) Mr Torque (Nm) Cm Torque coefficient (-)
1 Introduction Renewable energy resources, such as solar, geothermal, biomass, and wind energies, have become significantly raised because of the shortage of traditional fossil energy, pollution, and global warming in recent years. Among them, wind energy becomes a research hotspot and therefore numerous research works have been carried out for improving the technology of power generation by wind [1–3]. Recently, vertical axis wind turbines (VAWTs) hav
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