This paper describes numerical analysis of the impulse turbine with fixed guide vanes, a high performance bi-directional air turbine having simple structure for wave energy conversion. A 3- dimensional incompressible viscous flow numerical anal ysis based on the full Reynolds-averaged Navier-Stokes equations was made to investigate the internal flow behavior. As a result, a suitable choice for the one of design factors have been clarified with the understanding of the internal flow from the numerical analysis.
For wave energy conversion, the air turbine, which is called Wells turbine, has been investigated for many years. It has been widely applied for ocean-wave energy conversion, mainly due to its simple structure at present. The Wells turbine has however some inherent shortcomings; relatively lower efficiency, maintenance, higher axial thrust and noise in the case of high power specification because the circumferential speed of the rotor is essentially quite high (K. kaneco et al. 1986). The impulse turbine with self-pitch-controlled guide vanes has recently been proposed to overcome these drawbacks. It was clarified that the turbine can be operated with higher turbine efficiency and lower rotational speed than those of the Wells turbine (T. Setoguchi et al. 1995, T. Setoguchi et al. 1996). The impulse turbine with self-pitch-controlled guide vanes has a disadvantage of the maintenance of pivots on which the guide vanes are rotated automatically in a bi-directional air flow. Therefore, the authors studied the impulse turbine with fixed guide vanes for higher efficiency in a lower rotational speed than the W ells turbine. In this study, so as to develop more practical turbine for wave energy conversion with simple structure, the numerical flow analysis was carried out to grasp the relationship between the characteristics of turbine and the internal flow structure of impulse turbine with fixed guide vanes under steady flow conditions.
