Abstract:
A hydroelectric power station has an energy unit including a turbine and a generator. The impeller of the turbine includes an impeller ring and turbine blades. The radially outer ends of the turbine blades are fixed to the inner surface of the impeller ring, and the radially inner ends of the turbine blades are free and together form a central passage. The impeller ring is surrounded by the generator and acts as a bearing therefor.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is the national phase of PCT/EP2011/002010, filed Apr. 20, 2011, which claims the benefit of German Patent Application No. 10 2010 018 804.2, filed Apr. 29, 2010. 
     TECHNICAL FIELD 
     This disclosure relates to the field of water turbines or pump turbines. Such turbines have long been known in a large variety of configurations. 
     BACKGROUND 
     In the course of growing scarcity and increasing prices of energy, efforts are also increasingly undertaken to exploit water courses with low heights of fall and/or volume flows. Constructions are also applied in this process which are characterized by an especially simple configuration. 
     A hydroelectric power plant is known from U.S. Pat. No. 4,755,690 B1, comprising a dam which extends transversely to the direction of flow. Numerous power units are provided which respectively comprise a machine set with a turbine and a generator which have a common shaft. The individual machine sets are arranged in lines adjacent to one another and on top of one another and can be lowered to their working position by means of lifting devices. Only simple and sturdy constructions of the aforementioned machine sets can be considered in courses of rivers with low quantities of water and low flow velocities or low heights of fall. Seasonal differences in water quantities need to be taken into account in such courses of river as the differences between high water and low water can be very large. Rocks, driftwood or other bodies may be entrained during rushing flow as well as at low water. Such materials may cause damage to the machine set and blockage of the flow conduit of the turbine. 
     The invention is based on the object of providing a hydroelectric power plant which In one aspect, a miniature hydroelectric power plant of sturdy and simple configuration is provided that is especially suitable for the aforementioned conditions. 
     In another aspect, a turbine of the power plant includes a plurality of turbine blades which are arranged in the manner of marine screw propellers. A blade wheel includes a ring which encloses the rotational axis of the blade wheel and which carries the turbine blades on its inner circumference. The blade wheel is free from a shall or hub such that the blades are only fixed to the aforementioned ring. They protrude generally radially from the ring towards the rotational axis of the blade wheel. They are not fixed in any manner at their free ends. Instead, a passage remains between the free ends of the turbine blades through which any floating debris such as rocks, driftwood and the like is allowed to pass. 
     The stator of the generator encloses the ring and may be used by the same as a supporting bearing. 
     The power unit consisting of turbine and generator may be used in a river power plant, but also at locations where a flow occurs such as the coastal regions of bodies of water such as oceans. 
     The power plant may be used in a dam which is installed in the course of a river as a flow obstruction and is generally used for river training in order to decrease high flow velocities for example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained in closer detail by reference to the enclosed drawings, which show in detail; 
         FIG. 1  shows the principal arrangement of a power unit with an inlet and a suction tube; 
         FIG. 2  shows an apparatus similar to  FIG. 1 , but with two power units switched in succession; 
         FIG. 3  shows a power unit with a cooling device;  FIG. 3.1  shows an open cooling system;  FIG. 3.2  shows a closed cooling system; 
         FIG. 4  shows a power unit with an alternate configuration of the turbine blades; 
         FIG. 5  shows an apparatus similar to that according to  FIG. 4 , but in a tandem arrangement of two power units; 
         FIG. 6  shows a schematic overall view of a retaining dam and power units; 
         FIG. 7  shows a retaining dam in a perspective view; 
         FIG. 8  shows an axially end view of a turbine with parts of a generator; 
         FIG. 9  shows an axially sectional view of two power units switched axially in series; 
         FIG. 10  shows a schematic elevated view of a power plant in a vertical plane of intersection placed in the direction of flow; 
         FIG. 11  shows a power plant in a view similar to the one according to  FIG. 10 ; 
         FIG. 12  shows a further power plant in a view similar to the one according to  FIG. 10 ; 
         FIG. 13  shows a further power plant in a view similar to the one according to  FIG. 10 ; 
         FIG. 14  shows a further power plant in a view similar to the one according to  FIG. 10 ; 
         FIG. 15  shows a hydroelectric power plant with a cassette which can be inserted and carries a power unit in a vertical sectional view placed in the direction of flow; 
         FIG. 16  shows the item of  FIG. 15  in a schematic view; 
         FIG. 17  shows a power unit in an axial sectional view; 
         FIG. 18  shows a power unit in an axial sectional view with a cooling device; 
         FIG. 19  shows a power plant with a hubless turbine, to which a revolving outlet sleeve is connected; and 
         FIG. 20  shows a detail in connection with the item according to  FIG. 19 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  schematically shows a power unit  1  as a relevant component of a hydroelectric power plant. The power unit  1  comprises a turbine with a blade wheel ring  2 . 1 . The turbine is enclosed by an electric generator  6 . A distributor  3  is provided upstream of the turbine  2 . It comprises fixed or adjustable guide blades  3 . 1 . Water flows in the radial direction towards the distributor  3 . It will be deflected in the axial direction. A suction pipe  4  arranged downstream of the power unit. 
     The turbine  2  includes turbine blades  2 . 2  that are rigidly connected with the blade wheel ring  2 . 1 . Their radially inner ends do not reach up or axially extend to the rotational axis  2 . 3  of the turbine  2 , so that an opening remains between the ends. Floating debris entrained by the water is allowed to pass through this opening. 
     The embodiment shown in  FIG. 2  is arranged similar to the one according to  FIG. 1 . However, two power units  1  are provided in this case. 
     The distributor  3  forms a constricting flow channel. The flow extends without any deflection in the direction of the rotational axis  2 . 3 . 
     A bar grating  5  may be provided upstream of the distributor  3 . It has the general shape of a cone, which appears in the illustration as an arrow. The bar grating  5  may also have other shapes such as a-spherical cap or be generally planar. 
       FIG. 3  illustrates in a highly schematic manner a further power unit  1  with a turbine  2  according to the configuration as already described above. The turbine is therefore hubless. The turbine  2  is enclosed by an annular cooling chamber  7 . It comprises an inlet  7 . 1  and an outlet  7 . 2  for the cooling medium. The cooling system is provided with the task of removing the heat occurring in the stator device.  FIG. 3.1  illustrates a passage or flow system in which cooling medium flows in from the upstream water  8  of the ring chamber through the inlet  7 . 1  and leaves the same through the outlet  7 . 2  again and flows to the downstream water  9 . A pump  7 . 5  can be provided in this case.  FIG. 3.2  shows a closed system with a pump  7 . 3  and a cooling device  7 . 4 . Closed systems are preferable when the water shows a high degree of pollution. 
     The power unit  1  as shown in  FIG. 4  comprises a turbine  2  with turbine blades  2 . 2  of a special or alternate configuration. The turbine blades  2 . 2  are curved in the downstream direction. The free ends of the turbine blades  2 . 2  therefore face in the direction towards the downstream water. This promotes the discharge of floating debris which is entrained by the water and prevents the adherence of foreign particles to the turbine blades  2 . 2 .  FIG. 5  shows a similar configuration, but with two power units  1 . 
       FIG. 6  illustrates a retaining dam  10 . It has an L-shaped contour as seen in a vertical sectional view placed in the direction of flow, comprising a vertical limb  10 . 1  and a horizontal wall  10 . 2 . The vertical wall  10 . 1  carries three power units with distributor and suction tubes. Only the suction tubes  4  are shown in the drawing. Only the upstream water  8  is shown. 
     The retaining dam  10  shown in  FIG. 7  comprises a vertical wall  10 . 1  and a base or horizontal wall  10 . 2 . The retaining dam is located in a river. The base  10 . 2  is placed on the riverbed and rigidly connected with the vertical wall  10 . 1 . The base  10 . 2  is situated on the downstream side. A recess with a circular bottom part or section  10 . 1 . 1  and a rectangular upper part or section  10 . 1 . 2  is disposed in the vertical wall  10 . 1 . A machine part in accordance with the invention can be inserted in this case from above and can also be extracted upwardly again. 
       FIG. 8  shows the turbine  2 . It comprises a rotational axis  2 . 3  which is simultaneously the rotational axis of the generator  6 . The turbine  2  comprises a plurality of blades  2 . 2  and further a blade wheel ring  2 . 1 . The blades  2 . 2  are rigidly connected with the blade wheel ring  2 . 1 . They are fixed to the inner circumference of the blade wheel ring  2 . 1 . The radially inner ends of the blades  2 . 2  on the other hand are completely free because the turbine  2  is free from a shall or hub. A relatively large cavity is disposed radially within the blades  2 . 2 . Floating debris or floating bodies can pass through this cavity during operation of the machine set. The turbine  2  is enclosed by a generator  6 . Axial bearings  13 ,  13  and radial bearings  14 ,  14  are disposed between the stator ring  6 . 1  and the blade wheel ring  2 . 1 . 
       FIG. 9  shows another embodiment. Two machine sets which respectively consist of a turbine  2  and the generator  6  are arranged axially one behind the other. This duplex arrangement leads to the higher energy yield in operation. The efficiency is therefore higher than in a single machine set with only one single unit consisting of a turbine  2  and a generator  6 . Moreover, the duplex configuration is more flexible in operation than a single configuration. It is not necessary to operate both units simultaneously. Instead, either or both units can be switched off or switched on. The blades  2 . 2  can be recognized again in the two turbines  2 , which are respectively carried by the blade wheel ring  2 . 1 . The blade wheel ring  2 . 1  is mounted in the stator ring  6 . 1 . A spacer flange is provided between the two units. A housing is associated with the two machine sets. 
     The axial distance between the two turbines should be as small as possible. In one example the axial distance may be between 1 and 3 mm. In another example, the axial distance may be less than approximately 1 mm. The two generators are arranged in such a way that they revolve in opposite directions. 
     In the embodiment according to  FIG. 10 , one power unit  1  will receive a vertical inflow from the upstream water  8 . A suction tube  4  is connected and may be, formed of a structure  11  made of concrete. 
     In the embodiment according, to  FIG. 11 , the upstream water  8  flows horizontally against the power unit  1 . The power unit  1  is attached to the retaining dam  10 . The suction tube  4  opens beneath the downstream water  9 . 
     In the embodiment according to  FIG. 12 , a structure  11  made of concrete is shown. It comprises an area  11 . 1  which is inclined against or relative to the vertical. The structure  11  also forms the suction tube  4 . 
     In the embodiment according to  FIG. 13 , the upstream water  8  flows vertically against the power unit  1 . The retaining dam  10  comprises a vertical wall  10 . 1 . The horizontal wall  10 . 2  is disposed upstream of the vertical wall  10 . 1  and, therefore beneath the upstream water  8 . A further vertical wall  10 . 3  is attached to the horizontal wall  10 . 2 , followed by a further horizontal wall  10 . 4 . The suction tube  4  is disposed in the space enclosed by the walls  10 . 2 ,  10 . 3  and  10 . 4  and immerses in or opens to the downstream water  9 . 
     In the embodiment according to  FIG. 14 , two spaced apart vertical walls  10 . 1 ,  10 . 3  are provided. The first vertical wall  10 . 1  dams up the upstream water  8 . The power unit  1  is attached to the first vertical wall  10 . 1 . The downstream end of the suction tube  4  is mounted in the second vertical wall  10 . 3 . Upstream water  8  will therefore be deflected and introduced into the turbine  2  of the power unit  1 . It then flows horizontally through the suction tube to the downstream water  9 . 
     The hydroelectric power plant shown in  FIG. 15  in a sectional view is a so-called overflow power plant. Module  50  is arranged as a concrete body for example. The drawing further shows a turbine  2  which is arranged according to the  FIGS. 8 and 9 , comprising one or two or more blade wheels. Module  50  comprises a vertical shaft (also see  FIG. 6 ). A cassette  51  can be inserted from above into the vertical shaft. The cassette  51  carries the complete power unit  1 . A single module can accommodate several such cassettes  51  and therefore also several shafts. A bar grating  5  is provided upstream of the module. The bar grating is approximately provided with the shape of a quadrant in this embodiment. It could also be provided with a different configuration. This embodiment is extremely economical since it is simple in its configuration and easy to mount and maintain. 
       FIG. 17  shows additional detail concerning the turbine  2  and generator  6 . An axial bearing  13  is disposed between the blade wheel ring  2 . 1  of the turbine  2  and a housing  12 , namely at both axial ends of the blade wheel ring  2 . 1 . Radial bearings  14  are disposed between the blade wheel  6 . 1  of the generator  6  and the blade wheel ring  2 . 1 .  FIG. 18  shows the power unit  1  of  FIG. 17  with the cooling chamber  7 . 
       FIG. 19  shows a power plant and a hubless turbine  2  in a vertical sectional view placed in the direction of flow. An outlet sleeve  2 . 5  is connected to the blade wheel ring  2 . 1 . The outlet sleeve  2 . 5  is connected in a torsion-proof manner with the blade wheel ring  2 . 1 , and is optionally also integrally arranged with the blade wheel ring. The outlet sleeve  2 . 5  has the shape of a trumpet tube. It can also be cylindrical or approximately cylindrical. It offers the following advantage: the sleeve expands like a conventional suction tube, as is illustrated. Since the outlet sleeve  2 . 5  revolves together with the blade wheel ring  2 . 1  of the turbine  2 , the likelihood of flow separation on the inner walls of the outlet sleeve will be reduced in comparison with a suction tube with fixed walls. This means that the length of the sleeve can be smaller than the length of a conventional suction tube. Considerable construction costs can be saved thereby. The aforementioned outlet sleeve  2 . 5  can also be used in turbines of other configurations. It therefore need not be connected in a torsion proof manner with the blade wheel of the turbine. 
     The axial extension of the outlet sleeve  2 . 5  can also be substantially smaller than shown herein. Even an axial length of 10% of the diameter at the beginning of the outlet sleeve  2 . 5  provides the aforementioned advantage.