Abstract:
This hydraulic machine comprises a wheel supported by a shaft ( 5 ), the wheel and the shaft being able to rotate about a vertical axis (X 5 ) while a radial hydrostatic or hydrodynamic bearing ( 100 ) is formed between, on the one hand, a radial peripheral surface ( 52 ) of the shaft and, on the other hand, an internal radial surface ( 102 ) of a member ( 101 ) that is fixed relative to the vertical axis. The bearing ( 100 ) extends between two edges ( 121, 122 ) which, in normal operation, constitute regions for the removal of a film of water formed in the bearing. At least one cavity ( 130 ) is created in the fixed member ( 101 ) and opens onto its internal radial surface ( 102 ) near a first edge ( 122 ) of the bearing. The machine comprises means ( 131, 132, 133 ) for placing the cavity ( 130 ) in fluidic communication with a volume (V 1 ) situated outside the bearing near the second edge ( 121 ) of the bearing ( 100 ). That allows some (E 2 ) of the film of water from the bearing ( 100 ) to be removed towards the second edge ( 121 ) if the bearing becomes obstructed near the first edge ( 122 ).

Description:
BACKGROUND OF THE INVENTION 
     1. Field of The Invention 
     The present invention relates to a hydraulic machine that has a wheel supported by a shaft, said wheel and said shaft being mounted to move in rotation about an axis. The wheel of such a machine is designed to have a forced flow of water pass therethrough. Such a forced flow is a driving flow when the machine operates as a turbine. Such a flow is a driven flow when the machine operates as a pump. 
     2. Brief Description of the Related Art 
     In such a machine, a radial hydrostatic bearing can be provided around the shaft, with the function of taking up the radial forces to which said shaft is subjected. Such a bearing can be provided around an upper portion, around a lower portion, or around an intermediate portion of the shaft. It is known that a hydrostatic bearing can be equipped with an expansion seal, e.g. an inflatable seal, that makes it possible to protect the bearing from rising polluted water when the machine and the system for feeding water to the bearing are shut down. Such an inflatable seal is expanded during shutdowns of the machine, so as to isolate the bearing from its environment. Under normal operating conditions, the flow rate of water brought to the bearing is removed via the top and via the bottom of the bearing, thereby making it possible to procure both lift for the bearing and also removal of the energy dissipated by fluid friction, by generating of a continuous film of water. In the event that an inflation seal remains jammed in the expanded configuration, the water in the bearing cannot be removed towards the bottom of the bearing, which disturbs the flow of the water and the operation of the bearing. The lift of the bearing is reduced and the water that is held captive in the lower portion of the bearing tends to heat up, with a risk of the film of water being totally or partially transformed into steam, and a risk of the shaft coming into contact with the stationary bushing of the bearing. 
     These problems can also arise with a bearing that is not provided with an inflatable seal and in which removal of water from the bearing is obstructed, upwards or downwards, by any other obstacle. 
     Analogous problems can arise with horizontal-axis machines, which machines can also be equipped with hydrostatic or hydrodynamic seals. 
     It is also known, from U.S. Pat. No. 4,071,303, to provide the outside surface of a pump rotor with recesses for feeding a water bearing. Those recesses are connected to the upper edge and to the lower edge of the rotor via channels for removing solid bodies that could penetrate into the recesses. In the event that the bearing is obstructed, in the upper portion or in the lower portion, the film of water that makes up the bearing cannot be removed and might be transformed into steam, thereby limiting the lift of the bearing or reducing said lift to zero. 
     SUMMARY OF THE INVENTION 
     More particularly, an object of the invention is to remedy those drawbacks by proposing a hydraulic machine equipped with a radial hydrostatic bearing that operates more reliably. 
     To this end, the invention provides a hydraulic machine including a wheel supported by a shaft, the wheel and the shaft being mounted to move in rotation about an axis, while a radial hydrostatic or hydrodynamic bearing is formed between firstly a radially peripheral surface of the shaft and secondly a radially inside surface of a member that is stationary relative to the axis, the bearing extending between two edges that, when the bearing is operating normally, constitute removal zones for removing a film of water that is formed in the bearing. Said machine is characterized in that at least one cavity is provided in the stationary member and opens out onto its radially inside surface in the vicinity of a first one of the two edges of the bearing, and in that the stationary member is provided with means for putting the cavity into fluid communication with a volume situated outside the bearing, in the vicinity of the second of the above-mentioned two edges, the cavity and the communication means being suitable for removing a fraction of a flow forming the film of water, in the event that removal of the film is impossible at the first edge. 
     By means of the invention, in the event that the water of the radial hydrostatic or hydrodynamic bearing is prevented from being removed in the vicinity of a first edge that may be a top, bottom, front, or back edge, depending on whether the machine is of vertical or of horizontal axis, the cavity and the communication means provided in the stationary member make it possible to remove water from the bearing towards the other edge thereof, thereby avoiding generating a zone of dead water in the bearing. The flow of water in the bearing can thus be maintained, even in the event of obstruction of one of the edges of the bearing, thereby making it possible to maintain the lift of the bearing. 
     According to advantageous but non-essential aspects of the invention, such a machine may incorporate one or more of the following characteristics: 
     An expansion seal is disposed in the vicinity of the edge of the bearing that faces towards the wheel. In which case, when the machine is of vertical axis, the cavity is advantageously provided above the expansion seal, in the vicinity of the lower edge of the bearing that faces towards the wheel, while the communication means connect the cavity to a volume of the machine that is situated above the upper edge relative to the bearing. When the machine is of vertical axis, the cavity may be provided in the vicinity of the upper edge of the bearing, while the communication means connect the cavity to a lower portion of the bearing, above the expansion seal that is disposed below the lower edge of the bearing. 
     The cavity is an annular groove provided in the stationary member. In a variant, the cavity is formed by an association of a plurality of non-touching cavities that open out onto the radially inside surface of the stationary member, and each of which is connected to a duct provided in the stationary member and belonging to the communication means. 
     The communication means include pressure reduction means. 
     The communication means include at least one duct connecting the cavity to the volume situated in the vicinity of the second edge of the bearing. 
     Means are provided for determining the water pressure in a duct belonging to the communication means. In which case, the pressure determination means are advantageously suitable for delivering a signal representative of the water pressure in the above-mentioned duct to a control unit for controlling the machine. 
     The cavity extends at an axial distance from the first edge that has a value less than 10% of the axial dimension of the bearing, and preferably less than 5% of said axial dimension. 
     The cavity has an axial dimension having a value lying in the range 2.5% of the axial dimension of the bearing to 5% of said axial dimension. 
     The cavity has a radial depth having a value at least twenty-five times greater than the radial thickness of the bearing, and preferably fifty times said radial thickness. 
     The invention also provides an installation for converting hydraulic energy into electrical or mechanical energy, or vice versa, said installation including a hydraulic machine as mentioned above. Such an installation is more reliable than state-of-the-art installations insofar as it makes it possible to accommodate any obstruction of a radial hydrostatic bearing, in the vicinity of one of the edges thereof, namely its upper edge or its lower edge. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be better understood and other advantages of the invention appear more clearly from the following description of three embodiments of a machine and of an installation that comply with the principle of the invention, the description being given merely by way of example and with reference to the accompanying drawings, in which: 
         FIG. 1  is an axial section view showing the principle of a machine and of an installation in a first embodiment of the invention; 
         FIG. 2  is a view on a larger scale of the detail II in  FIG. 1 ; 
         FIG. 3  is a view on a larger scale of the detail III of  FIG. 1  when an inflatable seal of the installation is jammed; 
         FIG. 4  is a view analogous to  FIG. 3  for a machine and an installation in a second embodiment of the invention; and 
         FIG. 5  is a view analogous to  FIG. 3  for a machine and an installation in a third embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The installation I shown in  FIG. 1  includes a Francis turbine  1  whose wheel or “runner”  2  is fed from a casing  3  into which a forced-flow duct  4  opens out. The turbine  1  also includes a shaft  5  on which the wheel  2  is mounted and that rotates with said wheel about a vertical axis X 5  that is also the longitudinal axis of the shaft  5 . The shaft  5  rotates the rotary portion of an alternator  6 . 
     Between the casing  3  and the wheel  2  there are disposed two series of stationary guide vanes  71  and of wicket gates  72  whose function is to guide and to regulate a flow E that is coming from the duct  4  and from the casing  3  and that is to pass through the wheel  2  towards a suction duct  8 . 
     The wheel  2  is provided with blades  21  that extend between a ceiling  22  and a belt  23 . 
     The elements  3  and  4 , and the civil engineering structure that support the turbine  1  are part of a stationary structure  9  relative to which the wheel  2  rotates about the axis X 5 . 
     The wheel  2  is fastened to the lower end  51  of the shaft  5  or “base of the shaft”, by means of screws  10  that are represented by lines marking their axes. The base of the shaft may be formed integrally with the remainder of the shaft, or else be mounted thereon. 
     In order to withstand the radial forces to which the base  51  of the shaft is subjected, a hydrostatic bearing  100  is formed between the radially outside surface  52  of the base  51  of the shaft and a radially inside surface  102  of a bushing  101  of annular shape that is disposed around the base  51  of the shaft. In  FIGS. 2 to 4 , the radial thickness e 100  of the bearing  100  is exaggerated in order to make the drawing clearer. 
     A flow E 1  of clean water is delivered to the bearing  100 , from the forced-flow duct  4 , by means of a duct  103  connected to a tapping  104  provided in the bushing  101 . In order to make the drawing clearer, the connection between the ducts  4  and  103  is not shown in the figures. The tapping  104  is equipped with a series of diaphragms  105  that make it possible to limit the pressure of the flow E 1  downstream. The tapping  104  opens out into a channel  106  that feeds a depression  107  provided in the surface  102  and making it possible to distribute the flow E 1 . This makes it possible to force water into the bearing  100  in order to guarantee that a continuous film of water is provided around the surface  52 . 
     In the present description, the words “top”, “bottom”, “upper”, and “lower”, and “upwards” and “downwards” correspond to the installation I being disposed in an operating configuration in which the axis X 5  is vertical and the top of a member points towards the top of  FIG. 1 , while the bottom of the member points towards the bottom of  FIG. 1 . The adjective “upper” describes a portion of a member that points towards the top, conversely to a “lower” portion that points downwards. 
     A flange  110  is mounted at the bottom portion of the bushing  101  by means of fastener screws  111 . This flange co-operates with the bushing  101  to define a housing for receiving an inflatable seal  112  that is suitable for coming into abutment against the surface  52  depending on whether or not it is fed with pressurized fluid, which fluid is pressurized water in this example. The inflatable seal  112  is a type of expansion seal that makes it possible to protect the bearing  100  from water rising from the wheel  2 . Other types of expansion seal may be used with the invention, e.g. an axial seal. 
     Reference  121  designates the upper edge of the bearing  100 , i.e. the upper limit of the gap of small thickness e 100  defined between the surfaces  52  and  102 , and in which a film of water is formed from the flow E 1 . In practice, the edge  121  is situated at the same height as the upper edge of the surface  102 . Similarly, reference  122  designates the lower edge of the bearing  100  that is defined by the lower edge of the surface  102 , above the housing for receiving the seal  112 . 
     An upper tank  125  is mounted on the bushing  101  and defines an annular volume V 1 , above the edge  121  and radially around the portion of the surface  52  that is not facing the surface  102 . The tank  125  carries two seals  126  that come into abutment against the surface  52 , in order to avoid upward water leaks. The volume V 1  is connected via an overflow (not shown) to the sump well of the installation I, i.e. to the portion of the installation in which the leaks are collected, before they are removed downstream. 
     When the bearing  100  is operating normally, i.e. when the shaft  5  is rotating about the axis X 5 , the flow E 1  forms a film of water inside the bearing  100 , between the edges  121  and  122 , and is then removed upwards and downwards, as indicated respectively by arrows F 1  and F 2  in  FIG. 2 . This continuous removal of the flow E 1  from the bearing  100  guarantees the lift of said bearing. 
     In the event that the turbine  1  is shut down, and in order to prevent potentially polluted water from rising towards the inside of the bearing  100 , the inflatable seal  112  is put under pressure, so that it shrinks radially towards the axis X 5  and comes into abutment against the surface  52 , thereby forming a leaktight barrier. 
     When the turbine  1  is started up again, and before the shaft  5  is caused to start rotating, the seal  112  normally resumes its configuration shown in  FIG. 2 , in which it is spaced apart from the surface  52 . However, it can happen that the seal might be damaged and remain in the configuration in which it bears against the surface  52 , even though the shaft  5  is rotating, as shown in  FIG. 3 . In such a situation, the fraction of the flow E 1  that is normally removed from the bearing  100  at the lower edge  122 , as indicated by arrow F 2 , could remain captive in the bearing  100 , which would be detrimental to operation thereof, in particular because the lift would be reduced and because that would give rise to localized heating of the film of water, or indeed to transformation thereof into steam. 
     An annular grove  130  is provided in the bushing  101  and opens out onto the surface  102  all the way around the axis X 5 . Reference d 1  designates the axial distance between the groove  130  and the edge  122 . The distance d 1  is the distance between the lower edge of the groove  130  and the edge  122 . Reference h 100  designates the height or axial length of the bearing  100 , said distance and said height being measured parallel to the axis X 5 . The distance d 1  is chosen to be less than 10% of the height h 100 , and preferably to be less than 5% of said height. 
     Reference h 130  designates the height or axial length of the groove  130 , as measured parallel to the axis X 5 . The height h 130  is considerably smaller than the height h 100 , so that the presence of the groove  130  does not disturb the thickness e 100  over most of the bearing  100  that is situated above the groove  130 . For example, for a bearing  100  of height h 100  lying in the range 300 millimeters (mm) to 400 mm, the groove  130  has an axial height h 130  lying in the range 10 mm to 15 mm. In practice, the value of the axial height h 130  represents in the range 2.5% to 5% of the axial height h 100 . 
     Reference p 130  designates the radial depth of the groove  130 , i.e. the depth over which it extends into the bushing  101  from the surface  102 . This depth is at least twenty-five times greater than the thickness e 100 , and is preferably greater than fifty times said thickness. 
     The groove  130  is in communication with four ducts  131 , only one of which is visible in  FIG. 3 , and that are distributed uniformly in the bushing  101  about the axis X 5 . Each duct  131  extends along an axis X 131  parallel to the axis X 5  and connects the groove  130  to a housing  132  in which a plurality of diaphragms  133  are disposed, and that opens out into the volume V 1 . The ducts  131  are separated from the bearing  100  by the material of the bushing  101 , by means of the value of the depth p 130 . 
     Thus, in the event that the seal  112  remains jammed in the expanded configuration, thereby preventing the flow E 1  from being removed downwards, the corresponding fraction E 2  of the flow E 1  can flow into the groove  130  and into the ducts  131  and then through the diaphragms  133 , to reach the volume V 1  from which it can be removed to the sump well. This thus makes it possible to guarantee that the water in the bearing  100  flows continuously in its lower portion, even in the event of malfunctioning of the inflatable seal  112 . 
     A fraction of the flow E 1  continues to be removed from the bearing  100  at the edge  121 , as indicated by arrow F 1 . This fraction joins the flow E 2  in the volume V 1 . 
     The diaphragms  133  guarantee head loss at the housing  132 , so that, when the inflatable seal  112  is operating correctly, the total head loss through the portions  130 ,  131 , and  132  is greater than the head loss at the edge  122 , so that the flow in the direction indicated by arrow F 2  in  FIG. 2  is given preference. 
     The elements  130  to  133  also enable any polluted flow rising from the wheel  2  in the event of ineffectiveness of the inflatable seal  112  during a shutdown to be removed directly to the volume V 1 . Such polluted water can be drained through the groove  130 , through the ducts  131 , and through the housings  132 , thereby making it possible to protect the bearing  100  from pollution. 
     A tapping  134  opening out into one of the ducts  131  is connected to a pressure gauge  135  that indicates the water pressure inside at least one of the ducts  131 . The pressure gauge  135  can deliver a signal S 135  representative of the pressure inside the duct(s)  131  to a control unit  200 . This signal enables the unit  200  to detect an operating defect, insofar as a variation in pressure in one of the ducts  131  corresponds to the bottom outlet of the bearing  100 , at its edge  122 , being obstructed or, during a shutdown, to the seal  112  leaking. The unit  200  can thus modify the operating conditions of the turbine  1  by taking account of such an anomaly, e.g. by sending to the wicket gates  72  a signal S 200  aiming to reduce the rate of the flow E progressively. As a function of the signal S 135 , the unit  200  can also actuate an audible or visible alarm  136 . 
     The embodiment shown in  FIGS. 1 to 3  makes it possible to take account of an obstruction at the lower portion of the bearing  100 , independently of the use of the inflatable seal  112 . If the bearing  100  is obstructed in the vicinity of the edge  122  by something other than the seal  112 , the flow E 2  can flow through the volumes  130  to  132 . 
     In the second embodiment of the invention shown in  FIG. 4 , elements analogous to the elements in the first embodiment bear like references. A radial hydrostatic bearing  100  is defined between the outer radial surface  52  of the base  51  of a shaft  5  and the inner radial surface  102  of a stationary bushing  101 . An inflatable seal  112  is mounted on the bushing  101  by means of an annular flange  110 . 
     An annular groove  130  is provided in the vicinity of the upper edge  121  of the bearing  100  and connected to four ducts  131 , each of which extends parallel to an axis X 131  parallel to the axis of rotation X 5  of the shaft  5 . At its end opposite from the groove  130 , each duct  131  opens out into a housing  132  that itself opens out onto the surface  102 , above the lower edge  122  of the bearing  100 . Diaphragms  133  are disposed in the housing  132 , and they have the same function as the diaphragms of the first embodiment. 
     Reference d 1  designates the axial distance between the edge  121  and the groove  130 , reference h 100  designates the axial height of the bearing  100 , reference e 100  designates its radial thickness, reference h 130  designates the axial height of the groove  130 , and reference p 130  designates its radial depth. d 1  is less than 10% of h 100 , and preferably less than 5% thereof. h 130  lies in the range 2.5 to % of h 100  to 5% thereof. p 130  is greater than twenty-five times e 100 , and preferably greater than fifty times e 100 . 
     In the event that the upper portion of the bearing  100  is obstructed, e.g. by waste flowing from the volume V 1 , a fraction E 3  of the feed flow of the bearing  100  flows into the groove  130  and into the ducts  131 , and then flows back out at the lower portion of the bearing, i.e. in the vicinity of its lower edge  122 , through the housings  132 . Whereupon, the water coming from the upper portion of the bearing  100 , through the elements  130  to  132  can be removed downwards towards a volume V 2  situated under the bearing, together with the water coming directly from the lower portion of the bearing  100 , as indicated by arrow F 2  in  FIG. 4 . 
     The technical characteristics of the two above-described embodiments may be combined. In particular, a machine of the invention may have both a groove  130  in the bottom portion that is connected via ducts  131  to the volume V 1  and a groove  130  in the top portion that is connected via ducts  131  to the bottom portion of the bearing  100 . 
     The number of ducts  131  is not necessarily equal to four, and it can be adapted as a function of the foreseeable rate(s) of the flows E 2  and/or E 3  to be removed in the event of localized obstruction of the bearing. 
     Although advantageous for circumferentially distributing the flows E 2  and E 3 , it is not essential to use a peripheral groove  130 . A plurality of non-touching cavities opening out in the surface  102  may be provided, each of which extends over a predetermined angular sector, and is connected to a duct of the same type as the above-mentioned ducts  131 . 
     Finally, the rotary surface defined by the radial hydrostatic bearing may belong to a portion of the shaft that is formed integrally with the main portion thereof, as mentioned above as regards the base  51  of the shaft, or else it may belong to a portion mounted on said main portion. 
     In the two above-mentioned embodiments, the groove  130  and the communication means  131 ,  132 , and  133  are active for removing a fraction E 2  or E 3  of the film of water, only in the event of obstruction of the edge  122  or  121  of the bearing  100  that is in the vicinity of the groove  130 . When the bearing  100  is operating normally, the head loss induced by the diaphragms  133  is such that the film of water flows in preference via the edges  121  and  122 . 
     The invention is described and shown with a bearing  100  of the hydrostatic type, i.e. with a bearing whose lift depends essentially on the feed pressure at which the bearing is fed with water. As shown in  FIG. 5 , where all references under 200 are the same as on  FIG. 3 , the invention may also be implemented with a hydrodynamic bearing  300  in which the lift is obtained by the speed of rotation of the shaft. The invention is described above and shown with reference to a machine of vertical axis. However, the invention is also applicable to machines of horizontal axis, or indeed of slanting axis, which machines may also be equipped with hydrostatic or hydrodynamic bearings.