ABSTRACT

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 2- dimensional incompressible viscous flow numerical analysis based on the full Reynolds-averaged Navier-Stokes equations was made to investigate the internal flow behavior. Numerical results are compared with experimental data obtained by T.Setoguchi. 6) As a result, a suitable choice of design factor has been clarified with the understanding of the internal flow from the numerical analysis.

INTRODUCTION

Of the several types of variable air turbines for wave energy conversion investigated, a Wells turbine 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 case of high power specification because the circumferential speed of rotor is essentially quite high 2) The impulse turbine with self-pitchcontrolled guide vanes has newly been proposed to overcome these drawbacks and have clarified that the turbine can be operated with higher turbine efficiency and lower rotational speed than those of Wells turbine. The type of impulse turbine with self-pitch-controlled guide vanes has a disadvantage of maintenance of pivots on which the guide vanes are rotated automatically in a bi-directional air flow and therefore, the authors have been investigated the impulse turbine with fixed guide vanes for the higher efficiency in the lower rotational speed than of more Wells 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.

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