Abstract
Two types of vertical axis wind turbines (VAWTs) characterized by armless structure, i.e., low-center-of-gravity wind turbine (LCGWT) and butterfly wind turbine (BWT), had been compared in terms of the torque and power coefficients in the cases of symmetrical-blade rotor and cambered-blade rotor. The common rotor diameter is 0.4 m, and the rotor height of LCGWT is 0.25m and that of BWT is 0.3 m. The results are following: in both types, under the high tip speed ratio (TSR) conditions (λ > 0.75), cambered blade rotor was superior to symmetrical blade rotor. Under the low TSR conditions (λ ≤ 0.5 ), cambered-blade rotor showed higher performance than symmetrical-blade rotor in the LCGWT type, on the other hand, symmetrical-blade rotor showed better performance than cambered-blade rotor in the BWT type. According to the comparison between the cambered-blade LCGWT and BWT, BWT was superior to LCGWT under the condition of low TSR (λ ≤ 0.75), and LCGWT was superior to BWT under the condition of high TSR (λ ≥ 1.25). The maximum power coefficient (Cp = 0.113) was obtained in the case of cambered-blade BWT at wind speed of 6 m/s.
