Direct-Flow Hydroelectric Generator

a horizontal axial hydroelectric generator unit in which the rotor of the generator is mounted on the periphery of the runner of an axial hydroturbine. Water is fed to the turbine through a straight penstock with a circular cross section. An axial stator is mounted on a cowl located inside the penstock, and the radial thrust bearings of the turbine shaft are mounted inside the cowl. In order to prevent vibration at the periphery of the runner that would cause water to leak through the periphery seal into the generator, the runner is equipped with fixed blades, and the turbine is therefore classified as a propeller turbine. The turbine may be horizontal or inclined; and the draft-tube axis is straight.

Since the maximum efficiency of a propeller-type hydroturbine is higher than that of an adjustable-blade hydroturbine, the direct-flow generators’s maximum efficiency exceeds that of a capsule unit. In addition, direct-flow units are more convenient to operate than capsule units; but their efficiency is less if the head and loads are variable. Direct-flow generators are not widely used. Several such units with comparatively low power outputs (several megawatts) have been built in Germany, France, and the USSR.