The objective of this paper is to compare the performances of bi-directional turbines under irregular wave condition, which could be used for wave power conversion in the near future. The overall performances in connection with the behavior of oscillating water columnshave been evaluated numerically. The types of turbine included in the paper are as follows:
Wells turbine with guide vanes (WTGV);
turbine with self-pitch-controlled blades (TSCB);
biplane Wells turbine with guide vanes (BWGV);
impulse turbine with self-pitch-controlled guide vanes (ISGV) and
impulse turbine with fixed guide vanes (IFGV). In the study, the experimental investigations were carried out to clarify the performance under steady flow condition and then the numerical simulation was used for predicting the performance of the turbine under irregular wave condition, which typically occurs in the sea. As a result, it is found that the running and starting characteristics of the impulse-type turbines could be superior to those of the Wells turbine under irregular wave condition.
A Wells turbine is a self-rectifying air turbine which is expected to be widely used in wave energy devices with oscillating water columns (OWC). There are many reports that describe the performance of the Wells turbine both at starting and at running conditions (Inoue et al., 1988; Raghunathan and Tan, 1982). According to these results, the Wells turbine has inherent disadvantages: lower efficiency, poorer starting and higher noise level in comparison with conventional turbines. In order to overcome these weak points, many kinds of turbines have been proposed (Setoguchi et al., 1998; Inoue et al., 1989; Setoguchi et al., 1990; Setoguchi et al., 1996; Setoguchi et al., 1999). However, the comparison of characteristics of all these is limited to the turbine characteristics.
