Numerical and experimental investigation of counter-rotating twin-rotor wind turbine

With the ever-increasing global energy demand and the need for a rapid transition to renewable energy sources, the search for higher efficiency in wind turbine technology has gained great importance. In this context, in recent years, twin rotor wind turbines have been developed to increase the efficiency of wind power generation. In this study, a twin rotor counter-circulating wind turbine is designed, fabricated and subjected to extensive experiments. The main objective of the study is to understand the performance of twin rotor systems and to identify the factors that should be considered in the design of these systems. Considering aerodynamic efficiency and structural integrity, blades with NREL S822 profile were designed and manufactured. In the design, flow characteristics and energy conversion performance were tried to be optimized by ensuring that the front and rear rotors rotate in opposite directions. The experiments were carried out under laboratory conditions in an open channel wind tunnel. In the study, the blade angles were varied between 0°-24° and their effects on the system performance were investigated and it was determined at which angle combinations the twin rotor system works. In the experiments, the wind speed range was determined as 6-10 m/s and the turbine performance was analyzed at various speeds. The obtained torque values and power coefficients were compared with the data obtained from numerical analysis and the accuracy of the experimental results was evaluated The dual-rotor wind turbine system equipped with a direct-drive generator and NREL S822 blade profile demonstrated its most efficient performance in the 12°–3° blade configuration, achieving a power output of 189.50 W and an exergy destruction of 178.44 kJ/kg at a wind speed of 10 m/s. Compared to the single-rotor system, the dual-rotor configuration provided 23% to 66% higher power output, offering significant advantages in terms of energy efficiency and aerodynamic stability. The results obtained from both experimental and numerical analyses provide valuable insights for the potential large-scale applications of dual-rotor systems. This study aims to contribute to the future development of wind turbine technologies and represents an important step toward advancing renewable energy conversion.