The tube turbine is one of three types of tubular machine, which in turn is a hydraulic turbine utilized in river and tidal flow for the generation of AC electricity, driving an AC generator. Thus, it is part of a renewable form of alternating current generation. This type of hydraulic machine employs a Kaplan type of runner, which is fitted with either fixed or variable blades, as it is installed in the flowing water with its axis more or less horizontal.
The tube turbine transfers the mechanical rotatory power to the generator, which is installed outside the water path. The power transfer is done through an extended shaft. An appropriate gearbox is set up in between them to allow the generator speed to be optimized (improved). During maintenance, access to the generator and gearbox is much easier than in the bulb turbine type. However, the long shaft of the tube turbine can cause shaft whirling and bearing arrangement problems.
Below, a diagram of a tube turbine with the gearbox and generator.
