Parametric Study of Crowned Blade in Horizontal Axial Turbine

The horizontal axial turbine could extract kinetic energy from both wind and tidal stream. In this paper, a type of horizontal axial turbine was designed with a crown stalled on the blade tip and the turbine was analyzed in a tidal stream. Several turbines with different geometries of the crowns were compared, whose power coefficients were numerically simulated by the CFD method. Effects of the crown design parameters, such as crown setting directions and different widths on turbine efficiency were discussed. Furthermore, when the turbine worked at different tip speed ratio, the results were discussed, either. By analysis of the results, it is could be concluded that a circular crown was sufficient to eliminate blade tip loss caused by tip leakage flow. The upstream semicircle crown modified the corresponding side foil pressure distribution to the design value, and so did the downstream semicircle crown. In the ellipse crowns testing, turbine efficiency was approximately in line with the value of crowns width. When the turbine with the circular crown worked at a little higher tip speed ratio than the design value, the crown was effective as before.