Investigation and Optimization on Effective Parameters of a H-Rotor Darrieus Wind Turbine, Using CFD Method

The present study conducted a 2-dimensional numerical simulation using the Computational Fluid Dynamics (CFD) method for a Darrieus Vertical Axis Wind Turbine (VAWT). This study aims to investigate the effect of changing design and operational parameters on the performance of the Darrieus turbine. Power coefficient and torque are calculated to observe the turbine's performance, and their values ​​are compared in the different Tip Speed Ratios (TSR) and azimuth angles, respectively. Therefore, effective parameters such as free wind velocity, chord length, blade number, and airfoil profile are investigated. The results show that increasing the inlet velocity and chord length led to an increase in the efficiency of the turbine and formation of intense wake flow around the blades; however, increasing the number of turbine blades in small TSRs shows better performance, while when the rotor rotations number increases, the low solidity turbine with a lower number of blades has more efficiency. Also, the NACA0021 airfoil profile had higher Cp than other airfoil profiles and augments the wake flow downstream. An optimization method is provided to find the optimal operating and geometric conditions to achieve a higher value of Cp. The results show that the highest efficiency of Darrieus VAWT is achieved with an inlet velocity of 12 (m/s) and blade chord length of 0.2 (m) for a three-bladed turbine at TSR=2.5. It is also shown that Darrieus VAWT operates with lift force and needs an initial torque to start working by increasing the values ​​of Cp in the primary TSRs; the turbine's need for initial torque decreases.