The aim of this study is to clarify the effect of rotor blade profile on the performance of the Wells turbine operated at high Reynolds number. In the study, four kinds of blade profile were selected with regard to the blade profile of the Wells turbine. The experimental investigations have been performed for two solidities by model testing and numerical simulation. As a result, it has been concluded that a suitable choice, namely the preferable rotor geometry, is the blade profile of NACA0015. Furthermore, it has been found that the critical Reynolds number of the turbine seems to be around 4×105.
The Wells turbine is a self-rectifying air turbine which is expected to be widely used in wave energy devices with oscillating water column (OWC). There are many reports which describe the performance of the Wells turbine both at starting and running characteristics (Gato et al., 1996; Inoue et al., 1986a, 1986b; Raghunathan et al., 1987). According to these results, the Wells turbine has inherent disadvantages: lower efficiency, poorer starting and higher noise level in comparison with conventional turbines (Kim et al., 2001; Takao et al., 2002). In order to enhance the performance of the Wells turbine, some rotor blade profiles have been recommended by various researchers. It has been found by Setoguchi et al. (2003) that the optimum blade profile for small-scale Wells turbine which is installed in small wave energy device such as the navigation buoy (Setoguchi and Takao, 2001) (that is, the turbine is operated at low Reynolds number) is NACA0020. However, that for large-scale Wells turbine which is installed in wave energy plant such as the LIMPET system (Boake et al., 2002; Renewable Energy World, 2001), Islay, U.K. (that is, the turbine is operated at high Reynolds number) has not been clarified yet.
