The present invention relates generally to a water-power plant comprising a hydroelectric machine with a rotating shaft and an oil bearing. The bearing can be of the type thrust, guide or combined thrust and guide bearing

Water-power plants comprising oil bearings are suffering from oil vapor escaping from the bearings into the powerhouse. Since the sealing between the rotating shaft and the bearing oil enclosure cannot be made perfectly tight, oil vapor can escape to powerhouse environment. This is undesirable since the vapor can coat surrounding surfaces with oil - making them slippery and collecting dirt and contaminants from the environment. This can be especially undesirable on electrical contacts which are present in this type of equipment.

Several concepts have been developed to prevent vapor oil from escaping into the power house environment. One concept comprises an extraction fan connected directly to the top cover of the bearing’s oil basin (see e.g. RU 2 161 730 C2). In this way air is sucked via a radial clearance and a filter from the powerhouse environment into the compartment above the oil surface and again out of the compartment. This results in a continuous air flow through the compartment transporting the oil vapor out of the compartment. The air directly above the oil surface is continually refreshed, which leads to a substantially increased building rate of oil vapor. Another concept comprises knife seals between the basin and the rotating shaft to minimize the gap where oil vapor can escape. Since the seal is not perfect to the rotating shaft, and the knife seals wear easily due to contact during rough operation, the oil vapor still escapes.

The objective of the present invention is to provide a water-power plant with an oil bearing preventing oil vapor from escaping into the powerhouse without the application of knife seals and without increasing the building rate of oil vapor substantially. This objective is achieved by a water-power plant according to claim 1. Other favorable implementations of the invention are disclosed in the depended claims.

The invention will hereinafter be described in conjunction with the appended drawings:

Fig. 1 is a cross-sectional overview of water-power plant with an oil bearing;

Fig. 2 is a cross-sectional view of an oil bearing according to the present invention;

Fig. 3 is an enlarged cross-sectional view of a part of the oil bearing according to figure 2;

Figures 4 to 9 display other embodiments of the present invention.

Figure 1 displays schematically a water-power plant, which is designated as 1. The water-power plant comprises a powerhouse, which is designated as 2, and a hydroelectric machine, which is designated as 3. The hydroelectric machine 3 is located within the powerhouse 2. The hydroelectric machine 3 comprises a rotating shaft, which is designated as 4, and an oil bearing, which is designated as 5.

Figure 2 is a cross-sectional view of an oil bearing according to the present inventions. The bearing comprises a rotating part, which is designated as 6. The rotating part 6 is connected to the rotating shaft 4 (not shown in figure 2). The bearing comprises an oil basin, which is designated as 7 and which contains oil. In figure 2 the surface level of the oil is indicated by a horizontal line and a little triangle. The bearing further comprises a housing structure, which is designated by 8. The housing structure 8 is connected to the oil basin 7 and constructed to form at least two compartments confining the said compartments at least partially. A first compartment is designated by 9 and a second compartment is designated by 10. The compartments 9 and 10 will be described more thoroughly in relation to figure 3. The bearing comprises further a vapor extraction fan, which is designated by 11 and is connected to the housing structure 8 at a portion of the housing structure 8 confining the second compartment 10 in order to extract gas out of the second compartment 10. To establish this functionality the housing structure 8 comprises an opening at a suited location and the vapor extraction fan 11 comprises a suited hose which is connected to the opening. Optionally the housing structure 8 can comprise more than one of such openings and the vapor extraction fan 11 more than one hose being connected to the openings. Optionally the bearing can comprise more than one vapor extraction fan 11 each operating in the described way.

Figure 3 shows the compartments 9 and 10 in more detail. The bearing comprises at least two radial clearances located each between the rotating part 6 and a portion of the housing structure 8. In Figure 3 a fist radial clearance is designated by 12 and a second radial clearance is designated by 13. The first radial clearance 12 is located nearer to the oil surface, whereas the second radial clearance 13 is more distant to the oil surface. The first compartment 9 is confined by the rotating part 6, the surface of the oil, the oil basin 7, the housing structure 8 and one of the radial clearances 12. The second compartment 10 is confined by the rotating part 6, the housing structure 8 and two radial clearances 12 and 13. The radial width of the radial clearances 12 and 13 is at least 1 mm.

The term ‘clearance’ represents in the scope of this document a pure air gap without any additional sealing means. This implies that a compartment, which is confined by at least one clearance, is of course not air tight, since air can enter or leave the compartment via the clearance. Flowever the air flow through the clearance is somewhat restricted by the width of the clearance. Of course the term ‘clearance’ also implies a meaning of narrowness. Therefore the width of a clearance in the scope of the present invention is practically restricted to about 15 mm at the upper side. In a preferred embodiment of the present invention the radial widths of radial clearances 12 and 13 confining the compartment, to which the fan 11 is connected, are different, whereas the width of the radial clearance 13, which is more distant to the oil surface, is larger than the radial width of the radial clearance 12, which is located nearer to the oil surface. In a further preferred embodiment the radial width of the radial clearance 13 is more than 50% larger than the radial width of the radial clearance 12, i.e. the radial width of the radial clearance 13 is at least 1.5 mm.

Figure 4 displays a further embodiment of the present invention. In addition to the elements shown in Figure 3 the housing structure 8 comprises an additional portion, which is designated by 81. The portion 81 of the housing structure 8 forms an additional radial clearance, which is designated as 18. In the embodiment of figure 4 the first compartment 9 is confined by the rotating part 6, the surface of the oil, the oil basin 7, the housing structure 8 (portion 81 ) and the radial clearances 18, and the second compartment 10 is confined by the rotating part 6, the housing structure 8 and the two radial clearances 12 and 13. In this way the bearing comprises also an additional intermediate compartment, which is located between the first compartment 9 and the second compartment 10. Although the portion 81 is separately connected to the oil basin wall 7 it is regarded as a part of the housing structure 8. Alternatively one could regard the oil basin 7 ending just above the oil surface.

Figure 5 displays a further embodiment of the present invention. The only difference to figure 4 is that the portion 81 is now connected directly to the rest of the housing structure 8. It is clear that additional embodiments of the present invention can be derived out of the embodiments according to figure 4 or 5 by increasing the number of intermediate compartments.

The radial widths of the additional radial clearances in figures 4 and 5 is at least 1 mm. Optionally a vapor extraction fan can also be connected to an intermediate compartment in order to extract gas out of the intermediate compartment. Generally, the housing structure 8 is constructed in a way, that oil vapor escaping the first compartment 9 via the confining clearance (12 or 18) can enter the second compartment 10, where the oil vapor is extracted by the operation of the oil vapor extraction fan 11. In the embodiments according to figures 4 and 5 the oil vapor has to pass one or more intermediate compartments before entering the second compartment 10, whereas in the other embodiments the oil vapor enters the second compartment 10 immediately by leafing the first compartment 9.

Figure 6 displays a further embodiment of the present invention. In addition to the elements shown in Figure 3 the housing structure 8 comprises a filter element, which is designated as 16 and is designed and located in a way that ambient air can be sucked into the second compartment 10 via the filter element 16 by the operation of the vapor extraction fan 11.

Figure 7 displays a further embodiment of the present invention. In addition to the elements shown in Figure 3 the housing structure 8 is constructed to form an additional compartment, which is designated as 14. The additional compartment 14 is confined by the rotating part 6, the clearance 13, the housing structure 8 and a further radial clearance between the rotating part 6 and the housing structure 8. The further radial clearance is designated as 15 and the radial width of the further radial clearance 15 is at least 1 mm. The housing structure 8 comprises further a filter element, which is designated as 16 and is designed and located in a way that ambient air can be sucked into the additional compartment 14 via the filter element 16 by the operation of the vapor extraction fan 11.

Figure 8 displays a further embodiment of the present invention. In addition to the elements shown in Figure 3 the bearing comprises an oil vapor deflector, which is designated by 17. The oil vapor deflector 17 is connected to the rotating part 6 and is formed as a sleeve surrounding the rotating part 6. The oil vapor deflector 17 is located in the second compartment 10 and extends radially into the second compartment 10 by at least by 1 mm. In a preferred embodiment the oil vapor deflector 17 is bend towards the portion of the housing structure 8 forming the first radial clearance 12 as is shown in figure 8.

Figure 9 displays a further embodiment of the present invention. In addition to the elements shown in Figure 2 the bearing comprises an additional hose connecting the vapor extraction fan 11 with the housing structure 8 allowing the oil collected by the oil extraction fan 11 to be returned to the oil basin 7. If necessary the collected oil can be filtered before returning to oil basin 7. Optionally the oil collected by the vapor extraction fan 11 can be collected in a separate reservoir.

The embodiments according to figure 9 can be combined with any other embodiment. The embodiments according to figure 8 can be combined with the embodiments according to all preceding figures. Oil vapor deflectors can additionally also be applied within the intermediate compartments according to figures 4 and 5. The embodiments according to figure 7 can be combined with the embodiments according to figures 2 to 5. The embodiments according to figure 6 can be combined with the embodiments according to figures 2 to 5.

The functionality of the present invention is discussed in the following in comparison to the prior art solutions.

Since the radial widths of the radial clearances of the embodiments according to the present inventions are at least 1 mm and no other sealing means are necessary, the solutions according to the present invention can be produced much easier and are much more robust than the prior art solutions incorporating knife seals.

In contrast to the prior art solution disclosed in RU 2 161 730 C2 the present invention comprises two compartments and the continuous air stream is confined to the second compartment, which is separated by at least one radial clearance from the first compartment and the oil surface. The continuous air stream is indicated in Figure 2 by an arrow. Therefore only the amount of oil vapor, which diffuses through this clearance, is transported away, and therefore the building rate of oil vapor is not substantially increased. The diffusion rate and thus the escape rate of the oil vapor is further decreased by the means described in the paragraphs concerning figures 4, 5 and 8.

In case that the compartment confined inter alia by the oil surface is connected to the powerhouse ambient atmosphere by other ways than the described clearances as can happen due to manufacturing inaccuracies leading to small gaps e.g. between the housing structure and the oil basin, a small amount of air flow through these leaks might be established due to the operation of the fan. These air flow might somewhat increase the escape rate of the oil vapor. However even in this case the present invention is superior to the solution disclosed in RU 2 161 730 C2.

Since for the diffusion process of the oil the widths of the radial clearances on the side towards the oil surface are critical alone, the widths of the other radial clearances can be even larger. An increased width of these clearances has the additional benefit, that the pressure drop induced by the operation of the fan is reduced. Such a pressure drop can have a negative effect on the bearing operation.

With the aid of the filter elements according to figures 6 and 7 dust is prevented from being sucked into the compartments protecting the oil of the bearing from undue contamination. However most of the dust will be aspirated into the oil vapor extraction fan. And therefore without this element, the mixture of dust and oil would require more frequent cleaning of the fan and the compartments.

It is clear that the embodiment according to figure 9 results in recycling of the extracted oil.