Effects of design parameters on aerodynamic performance of a counter-rotating wind turbine

This study investigates the effects of design parameters on the aerodynamic performance of a counter-rotating wind turbine. The counter-rotating wind turbine has two rotors rotating in opposite directions on the same axis. It has been proposed on the basis of the theory which states that a configuration of two rotors having the same swept area on the same axis has a higher maximum power coefficient than a conventional configuration of a wind turbine having a single rotor. More design parameters are involved in the description of the counter-rotating wind turbine than of a wind turbine using a single rotor because of the complex phenomenon arising from the aerodynamic interaction between its two rotors, but influences of these parameters is yet to be fully understood. In this study, a modified blade element momentum theory for the counter-rotating wind turbine is developed to investigate the effects of these design parameters such as the combinations of the pitch angles, rotating speeds and rotors’ radii on the aerodynamic performance of the counter-rotating wind turbine.

► BEMT for the counter-rotating wind turbine is developed for a parametric study.
► Pitch angles, rotating speeds and radii of the two rotors are chosen as parameters.
► Maximum total power is obtained when each rotor shares the total power.
► The rotating speed of the rear rotor should be reduced for the maximum total power.
► Despite the decrease of the front rotor, it is possible to increase the total power.