Abstract
The bi-directional impulse turbine and the bi-directional flow collector for tidal energy conversion is investigated in this paper. The bi-directional impulse turbine with fixed guide vanes is adopted because the turbine has a high efficiency and an advantage of maintenance. The turbine characteristics of the combined system of impulse turbine and collector are investigated experimentally by using the water tunnel. This system is proved to produce the power by a tidal flow experimentally. Three types of flow collector A, B and C are investigated, where the maximum radius of collector A is smaller than the ones of collector B and C. The velocity ratio of collector A is much smaller than the one for the cases of collector B and collector C, and the output power of collector A is very small compared to the other collectors. Nevertheless, the effect of flow collector is large because velocity ratio of collector A is much larger than the one without collector. Among three cases of 0.5, 0.6 and 0.7 of hub-to-tip ratio, the difference of turbine performance is not so large, but it is observed that the case for 0.5 of hub-to-tip ratio has inferior performance and the case for 0.6 of hubto-tip ratio has the performance among them. Further, the comparison of circulating water tank test and towing tank test was done to show the effect of choking ratio of cross sectional area of channel.