Newsletter 2016.11 Index
Theme : "Mechanical Engineering Congress, 2016 Japan (MECJ-16)"
A unique idea “counter-rotating type turbo-unit” came into Kyushu Institute of Technology on January 25, 1998. In the unit, tandem impellers/runners connect directly to inner and outer armatures of a peculiar motor/generator. Both impeller speeds are automatically adjusted in response to the pumping discharge, while the rotational torques between both impellers/armatures are counter-balanced. That is, the angular momentum change through the rear impeller must coincide with that through the front impeller. Such adjustments contribute to suppress not only the unstable operation at the lower discharge but also the cavitation at the higher discharge, while the relative rotational speed is kept constant in an induction motor. The relative rotational speed between the tandem runners, in the generating mode, is higher than the traditional type single runner/armature speed. Such power units have promising advantages, for instance, (i) the induced voltage is higher at the same diameter, (ii) the diameter of the armature can be reduced at the same individual rotational speed, and then (iii) the rotational moments hardly act on the mounting bed. The counter-rotation, whose advantages were verified experimentally in the pumping and the generating modes, has been also applied to wind power units, tidal power units. These units are on stand-to work in the markets.
Turbomachine, Counter-Rotation, Pump, Turbine, Hydropower, Wind Power,Tidal Power
Fig. 1 Rotational torque acting on the armatures
Fig. 2 Operation in the field
Fig. 3 Performance of the model hydroelectric unit
Fig.4 Intelligent Wind Power Unit
Fig.5 Tidal stream power unit moored with a cable