The objective of this paper is to clarify the performance of impulse turbine with fixed guide vanes and to compare it with that of Wells turbine with guide vanes. As a result, a suitable choice of the design factors for the impulse turbine was shown for the inlet angle of rotor blade and the shape of guide vane. Furthermore, it was found that the running and starting characteristics of the impulse turbine were superior to those of the Wells turbine under irregular wave condition.
Several of the wave energy devices currently studied in the United Kingdom, Japan, Portugal, India, China and other countries make use of the principle of oscillating wave-air column (OWC) for converting wave energy to low pressure pneumatic energy which in turn can be converted into mechanical energy. In this case, the development of bidirectional air turbine has come up as an important problem. So far, a number of self-rectifying air turbines with different configurations were proposed, for example, a Wells turbine (Gato et al., 1988, 1993; Inoue et al., 1986a, 1986b; Kaneko et al., 1986; Raghunathan, 1995; Raghunathan et al., 1995; Setoguchi et al., 1990a, 1990b, 1998; White, 1995), the turbine using pitch-controlled blades (Neal, 1993; Salter, 1993; Sarmento et al., 1987; Setoguchi et al., 1997) and the other (Kaneko et al., 1992; Richards et al., 1986). Many reports describe the performance of Wells turbine both at running and starting conditions. According to these results, however, the Wells turbine has inherent disadvantages such as lower efficiency, higher noise and poorer starting characteristics in comparison with conventional uni-directional turbines. In order to overcome these drawbacks, Setoguchi et al. proposed an impulse turbine with self-pitch-controlled guide vanes (Kim et al., 1988; Maeda et al., 1994; Setoguchi et al., 1988, 1993, 1994).
