PERFORMANCE ANALYSIS OF WIND TURBINES WITH DIFFUSER AND SWEPT BLADES

This work presents a new performance analysis of diffuser-augmented wind turbine (DAWT) and curved blades (sweep effect), considering the influence of diffuser efficiency and thrust, in which a formulation for wake flow speed proposed by Uaz & Wood (2018). Blade element theory has been extended to include diffuser efficiency in the axial velocity formulation by Uaz & Wood (2018), which in turn modifies thrust and power. A correction for the thrust on the rotor proposed by Uaz & Wood (2016) is also added, in which a quadratic equation is used to incorporate the losses in the diffuser. An algorithm was developed and implemented to evaluate the performance of wind turbines with diffuser and sweep effect based on the Blade Element Momentum Theory (BEMT). The impact of the diffuser is evaluated by the augmentation factor, the ratio between the turbine efficiency and the Betz-Joukowsky limit. The comparison between the experiment and the algorithm takes into account the same rotor and diffuser used by Hoopen (2009), optimizing only the blade where it is inserted the sweep effect. The model was validated in comparison with experimental data from Hoopen (2009) and shows good agreement with the power, torque and thrust results for a speed of 10.0 m/s, the increase factor demonstrates good agreement for speeds of 7.0 m/s; 9.0; 10.0 and 11.0 m/s. The results obtained experimentally by Hoopen (2009) are: power of 531.0 W, torque of 7.10 N.m and thrust coefficient of 0.80. The results obtained from the work with a straight blade are: power of 532.6 W, torque of 7.10 N.m and thrust coefficient of 0.77. The optimized rotors with the 30 degrees and 40 degrees sweep effect generated greater performance in the DAWT. The rotor with the 30 degrees sweep effect generated a power of 542.3 W, torque of 6.94 N.m and a thrust coefficient of 0.60. The rotor with the 40 degrees sweep effect generated a power of 520.37 W, torque of 7.23 N.m and a thrust coefficient of 0.69. The present work shows relevant points for the current state of the art, as the theoretical model used presented satisfactory outcomes, demonstrating the feasibility of algorithms for analyzing wind turbine designs with diffuser and sweep effect.