High power immersed turbo-generator set having a gear box and external cooling

Claim 1

A high power immersed turbo-generator set having external cooling and being a gear box, wherein the generator set comprises: an elongated external housing having a longitudinal axis and immersed in a water duct; a turbine mounted on the rear portion of said housing on a shaft extending along the housing axis, the turbine having blades that project radially outwardly from said housing to be rotated by a flow of water along said duct; a gear box housed in an intermediate portion of said housing, driven by the turbine shaft, and driving an alternator shaft at higher speed than the turbine shaft, the alternator shaft extending into a front portion of the housing; an alternator rotor mounted on said alternator shaft in a front portion of said housing; an alternator exciter mounted on the alternator shaft to provide excitation current to the rotor; and an alternator stator surrounding the rotor and including windings, a magnetic circuit and a supporting casing which surrounds the magnetic circuit and is in contact therewith; said stator casing constituting a portion of the housing whereby a portion of the heat generated in the magnetic circuit is directly dumped into the water flowing along the duct; the alternator constituted by said rotor, said exciter and said stator being provided with a gas cooling circuit through which a cooling gas is made to flow; said cooling circuit including external cooling tubes disposed outside the housing to enable the cooling gas to be cooled by the water flowing in the duct, each of said tubes running from a front end orifice in the housing to a rear end orifice in the housing; the improvement comprising: the front end orifices being arranged in a staggered configuration occupying two different transverse drilling planes in front of the alternator stator, the longitudinal distance separating said transverse drilling planes being at least equal to the diameter of the orifices to avoid excessively weakening the mechanical strength of the housing in the vicinity of said drilling planes; an access tube being provided between the intermediate portion of the housing and the outside wall of the surrounding water duct to provide access to the inside of the housing from outside the duct; and wherein the front and the intermediate portions of the housing are of different diameters and are interconnected by a flange having an inside diameter equal to the diameter of the front portion and an outside diameter equal to the diameter of the intermediate portion, with the rear end orifices of the cooling tubes passing through said flange.