A Wells turbine has inherent disadvantages: lower efficiency and poorer starting characteristics. In this case, the guide vanes in front of and after rotor may be one of the most effective equipment for the improvement of the turbine performance. Several papers demonstrated the usefulness of 2D guide vanes so far. In order to achieve the further improvement of the performance of the Wells turbine, the effect of 3D guide vanes has been investigated experimentally by a model testing under steady flow conditions. And then, the running and starting characteristics under sinusoidally oscillating flow conditions have been obtained by a computer simulation using quasi-steady analysis. As a result, it is found that the running and starting characteristics of the Wells turbine with 3D guide vanes are superior to those with 2D guide vanes.
Several of the wave energy devices currently studied in the United Kingdom, Japan, Portugal, India and other countries make use of the principle of the oscillating water-air column for converting wave energy to low-pneumatic energy which in turn can be converted into mechanical energy. In this case, the development of a bi-directional air turbine has come up as an important problem. So far, a number of self-rectifying air turbines with different configurations have been proposed, including the Wells turbine (Gato et al., 1988; Inoue et al., 1986a, 1986b; Kaneko et al., 1986; Raghunathan et al., 1987, 1994; Raghunathan, 1995; Setoguchi et al., 1986; Suzuki et al., 1985; White, 1995), a turbine using self-pitch-controlled blades (Raghunathan et al., 1997; Sannento et al., 1987, Takao et al., 1997), an impulse turbine with self-pitch-controlled guide vanes (Setoguchi et al., 1996), an impulse turbine with fixed guide vanes (Setoguchi et al., 1999) and so on (Kaneko et al., 1992).
