Experimental investigation into the effects of blade pitch angle and axial distance on the performance of a counter-rotating tidal turbine

In order to investigate the influence of blade pitch angle and axial distance on the performance of the counter-rotating type horizontal-axis tidal turbine (HATT), a series of experiments were conducted in a wind tunnel under different installation conditions. The blades were designed based on the blade element momentum (BEM) theory, and the effects of configuration factors were actualized in two aspects: different combinations of the front and rear blade pitch angles and different axial distances of dual rotors. The test results indicate that the proper increase of blade pitch angles and axial distance can enhance the performance of a counter-rotating turbine by increasing the peak CP (power coefficient) value and widening high CP value area. However, more experiments are still needed in order to investigate the relationship between CP and axial distance under small blade pitch angles more precisely. Flow field investigation is also required to understand the wake structure and intensity around the blades with small pitch angles. The result in the wind tunnel is a reference for the experiment in the water tunnel.