No abstract

Pumped storage system contributes to adjust the electric power unbalance between day and night, in general. The pumping operation, however, may be unstable in the rising portion of the head characteristics, and/or bring the cavitation at the low suction head. To simultaneously overcome both weak points, the authors have proposed a superior pumping unit that is composed of counter-rotating type impellers and a peculiar motor with double rotational armatures. This paper discusses the operation at the turbine mode of the above unit. It is concluded with the numerical simulations that this type unit can be also operated acceptably at the turbine mode, because the unit works so as to coincide the angular momentum change through the front runners/impellers with that thorough the rear runners/impellers, namely to take the axial flow at not only the inlet but also the outlet without the guide vanes.

To cope with warming global environments, authors have proposed the counter-rotating type hydroelectric unit, which is composed of tandem runners and the peculiar generator with double rotational armatures. The unit can be provided for various water circumstances at not only the onshore but also the offshore. This paper discusses effects of setting angle and the number of runner blades on turbine performances and then optimum blade setting angles giving the maximum output and/or the maximum efficiency, namely the on-cam operation, are presented at various discharges/heads.