AIR-FILLED KAPLAN RUNNER

Abstract

A water-fed turbine includes a shaft and a Kaplan runner having a plurality of blades and a hub, the hub located at an end of the shaft and bearing the blades. Means are provided for generating dry air, as well as a means for supplying the turbine with a flow of the dry air. Means are also provided for evacuating air out of the turbine after the flow of dry air has flowed at least through the hub.

Claims

1. (canceled)

2-15. (canceled)

16. A water-fed turbine comprising: a shaft; a Kaplan runner comprising a plurality of blades and a hub, the hub located at an end of the shaft and bearing the blades; means for generating dry air; means for supplying the turbine with a flow of the dry air; and means for evacuating air out of the turbine after the flow of dry air has flowed at least through the hub.

17. The water-fed turbine according to claim 16, further comprising means to monitor or measure humidity of the air evacuated out of the turbine.

18. The water-fed turbine according to claim 16, further comprising an outlet chamber or tank configured to collect at least part of the air evacuated out of the turbine.

19. The water-fed turbine according to claim 18, wherein the outlet chamber at least partly surrounds the shaft.

20. The water-fed turbine according to claim 16, wherein the supplying means comprises an inlet duct inside the shaft.

21. The water-fed turbine according to claim 16, wherein the evacuating means comprises an outlet duct that is fixed to, or rotating with, or located inside the shaft.

22. The water-fed turbine according to claim 16, wherein the evacuating means comprises an outlet configured to evacuate the air into a water flow.

23. The water-fed turbine according to claim 16, wherein the supply means comprises means for varying a flow or frequency of the flow of dry air.

24. The water-fed turbine according to claim 23, wherein the flow or frequency of the flow of dry air is regulated based on a humidity degree or flow rate of the of the air evacuated out of the turbine.

25. The water-fed turbine according to claim 16, wherein the supplying means comprises a tank configured to store the dry air.

26. The water-fed turbine according to claim 16, wherein the supplying means comprises an air dryer.

27. A method for operating the water-fed turbine according to claim 16, the method comprising: generating the flow of dry air; supplying the turbine with the flow of dry air; and evacuating the air out of the turbine after the flow of dry air has flowed at least through the hub.

28. The method according to claim 27, further comprising measuring a humidity or a rate of flow of the air evacuated out of the turbine.

29. The method according to claim 28, further comprising varying the flow of dry air based on the humidity or rate of flow.

30. The method according to claim 27, wherein: the flow of dry air is supplied to the turbine through an inlet duct that is at least partly located in the shaft; and the air is evacuated out of the turbine through an outlet duct fixed to, or rotating with, or at least partly located in the shaft, or is evacuated through an outlet into a water flow.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0052] FIG. 1 shows an example of a known vertical Kaplan turbine;

[0053] FIG. 2 shows an example of a known horizontal Kaplan turbine, also usually referred as a bulb turbine;

[0054] FIG. 3 shows a turbine according to the invention;

[0055] FIG. 4 shows a more detailed view of a horizontal turbine according to the invention;

[0056] FIGS. 5A and 5B show variants of a vertical turbine according to the invention;

[0057] FIG. 6 shows another embodiment of a vertical or horizontal runner with an air exhaust in water;

[0058] FIG. 7 shows a more detailed view of a shaft of a turbine according to the invention;

[0059] FIG. 8 shows a dry air generating and supply system for a turbine according to the invention; and

[0060] FIG. 9 shows an example of control system to control a turbine or a process according to the invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0061] An example of a Kaplan turbine, or a turbine comprising a Kaplan runner, comprising a dry air supply system according to the invention is illustrated in FIG. 3, wherein the same reference numbers designate the same elements as discussed above in connection with FIGS. 1 and 2.

[0062] In this figure, a dry air generating system 10 is connected to a circuit 12 in order to inject a flow 120 of dry air into the turbine, for example into a duct 16 formed in the rotating shaft 126 and extending down to the hub 114, in particular in order to keep the interior of the runner hub dry.

[0063] The system 10 generates dry air from atmospheric or outside air. Referring to FIG. 8, the system may include a tank or accumulator 40 (see FIG. 8) for buffering the dry air, a dryer 44, and a filter 42 and/or a compressor. This dry air may be compressed, for example at a pressure sufficient to provide the dry air flow. For a given pressure, the corresponding dry air flow can be calculated or obtained.

[0064] For example, for a Kaplan runner operating in water, for example water of a cold Nordic river, which has a temperature close to zero degree Celsius in winter, the upper limit for the dry air dew point should be zero degree Celsius. This would allow to avoid condensation inside the runner hub even when water is almost down to 0 C.

[0065] Furthermore, to remove moisture already present in the hub, the dry air should have a lower dew point than 0 C.: a dew point around 5 C. or preferably 10 C., or 20 C. or 40 C. could be selected to allow some capacity to remove some moisture already present in the runner hub. The lower the dew point, the more moisture can be extracted from the runner hub.

[0066] A dryer (of the means for generating dry air) can be selected based on its dew point and air flow rate. The inventors have observed that a dew point at least 10 C. lower than the water temperature provides a good capacity for efficient moisture removal, assuming a complete hub air exchange in no more than 60 minutes. An example of dryer which can be implemented is a desiccant air dryer, for example a D2 modular desiccant dryer of Nano Purification Solutions, Inc, see for example www.n-psi. com, ref.17-100-0120, Issue 007, Series 2. The dryer can be a compressed air dryer using the pressure swing adsorption principle of drying compressed air, utilizing two identical columns each containing a hygroscopic desiccant bed. Other dryers can be used.

[0067] The humidity level or rate of this dry air can be measured to make sure condensation will not occur and/or to be able to drag some humidity from the runner hub, preferably even under the most adverse temperature conditions which is the coldest possible hub temperature when the runner is in operation, at rest or even during maintenance when runner can be exposed to ambient air temperature. In other words, this air has a dew point low enough to ensure no condensation is formed inside the hub and able to remove or absorb humidity from the hub.

[0068] The circuit 12 may comprise one or more regulating valve(s) 13 in order to regulate or to stop the flow 120 of dry air circulating in direction of the duct 16. The one or more valve(s) can be controlled by a control system of the unit, for example a computer or a processor (not represented in the figure), for example based on an information or a signal from a humidity sensor as explained below. An example of such a control system is illustrated in FIG. 9.

[0069] In particular, the flow 120 of dry air can be supplied to the Kaplan runner through the shaft 126, and more particularly through the duct 16 extending along the shaft. As illustrated in FIG. 3, the air 8 then circulates in the hub 114 where it is mixed with air already present therein and then evacuated through a return or evacuation duct 14 that may also be formed in the shaft 126 and flows outside the shaft through an air outlet 18. Alternatively, the return or evacuation duct 14 may be located outside the shaft; preferably it is against the shaft or fixed to the shaft, thereby rotating with it. An air outlet tank 22 may be connected to the air outlet 18 and may include means, for example a sensor, to monitor the air condition, in particular the humidity, inside the runner and particularly inside the hub 114. The flow 120 of dry air can be regulated based on information from the means or sensor about the humidity rate inside the hub.

[0070] A turbine of the Kaplan type is composed of different parts which are assembled together. Water can leak from the outside of the runner hub 114 into the runner hub in particular at the interfaces between the blades and their seals or where sealing flanges are present, at the runner cone for example. The flow of dry air which is circulated as explained above therefore becomes laden with humidity as it flows through the hub 114. The air at outlet 18 can therefore be moist air. Thus, the measurement of the humidity level or rate in the air at air outlet 18 is an indication of possible leaks in the turbine. This measurement of the humidity level or rate can be compared with a reference value or with the humidity level or rate of the flow 120 of dry air injected into the inlet duct 16. In other words, the air that flows through the runner can be tracked and/or analysed to check the humidity inside the runner and to detect the presence of any leakage. For example, as illustrated on FIG. 3, a chamber or tank 22 can be located at the outlet 18 and collect air which has flowed through the runner as explained above, such chamber or tank being provided with humidity sensor and/or a float (not represented on FIG. 3). It is also possible to exhaust the moist air directly into the river without circulating back to the chamber or tank 22. In this case, for example, a bluetooth sensor can be located in the runner cone. The above explanation, given in connection with a Kaplan turbine with a vertical shaft, also applies to a Kaplan turbine with a horizontal shaft or for a Kaplan turbine at any angle.

[0071] FIG. 4 is a more detailed example of a horizontal Kaplan turbine implementing the invention and showing details of the air flow in the hub 114. A flow of dry air 120 is injected into the runner through horizontal duct 16, then into the hub 114 and is swept through areas 30, 30of the hub possibly containing water or humidity resulting from water leaking from outside the hub into the runner. References 20 (blade seals), 20A (cone flange), 20B (hub filling port), 20C (at cone closing plate) are examples of various locations where water can leak into the runner. Similar locations are found in a vertical Kaplan turbine. As it travels through the hub, the dry air can thus be progressively laden with humidity or moisture. It may flow through parts of the runner located at, or closer to, the zone 32 of largest diameter. References 21A and 21B designate bushings.

[0072] FIGS. 5A and 5B are other embodiments of a vertical Kaplan runner implementing the invention and showing details of the air flow through or into the hub 114. The same references as in FIG. 4 designate the same elements and reference is made for these elements to the above description. Here the dry air may flow through parts of the runner. The duct 14 is preferably positioned so that it may capture air at locations where water may accumulate during operation (FIG. 5B) and/or when the machine is stopped (FIG. 5A).

[0073] The inlet 14to duct 14 (the drain) may be located at the bottom of the hub, as shown on FIG. 5A; this will depend on the operation of the machine and where the water should actually accumulate.

[0074] As shown on FIG. 5B, the inlet to duct 14 (the drain) may be located at the largest diameter of the runner, because when the machine rotates, water is going to flow to this area due to centrifugal forces.

[0075] In any of the embodiments given in this application, the inlet duct 16 may have a first section at least partly located in the shaft and a second section having a plurality of distributing ducts 16a, 16b (see for example on FIG. 5A), for example at least two ducts 16a,, 16b connected to the first section and extending from said first section laterally or at an angle with respect to the direction of the shaft. These distributing ducts 16a, 16b can distribute dry air at locations which are offset from the vertical axis of the runner.

[0076] FIG. 6 is a more detailed example of a vertical and/or horizontal Kaplan implementing the invention and showing details of the air flow through or into the hub 114 and the moisty air exhaust inside the water passage. The same references as in the preceding figures designate the same air inlet elements and reference is made for these elements to the above description. Here the dry air may flow through various parts of the runner. A moist air exhaust 35 can be positioned to exhaust the moist air directly to the water passage.

[0077] FIG. 7 shows a detail of the shaft 126 of an embodiment of the invention comprising both the inner duct 16 to introduce a flow 120 of dry air and the lateral duct 14 through which the moisture laden air 185 is evacuated. Air 185 can then be evacuated through the rotating outlet 18 and then possibly to a chamber or tank 22 which is fixed and located close to, or around, the shaft 126 with labyrinths 26 which can be fixed on the shaft in order to maintain a tight gap between the rotating parts (the shaft) and the static part (the tank 22, which is preferably fixed on static parts, and is for example centred around the shaft, without contact between the tank and the shaft). Thus the shaft, including the inlet and the outlet ducts 16, 14, is rotating while the exit tank 22 is preferably fixed with respect to the shaft, while being located close to or around it. The air can then be evacuated from the tank 22 through an outlet duct 27 to the atmosphere. The reference 24 designates at least one humidity sensor and/or a water level indicator (indicating a water level in the tank 22), which can provide information about the humidity and/or water level in the tank 22, thus giving a measurement of, or information about, the humidity level in the hub 114, and therefore an information about possible leaks of water from outside the turbine into the hub. The information about the degree or rate of humidity can be provided to a controller which can be programmed to regulate the volume and/or the frequency of the inlet air flow 120 and/or some maintenance plan based on the information. Alternatively, even without a controller, this information can be used to plan maintenance of the system, for example the replacement of one or more seal(s).

[0078] FIG. 8 shows an example of a dry air generating system 10 together with the air supply system 12 that can be implemented in the frame of the present invention. In this embodiment, one or more filter(s) 42, a dryer(s) 44 and a compressor feed a tank 40 with dry air. The pressure inside the tank 40 can be measured with a pressure gauge 46 and controlled by pressure sensor 48. The system may include a pressure limit or relief valve 49 to protect the tank. Dry air 120 can be supplied from the tank 40 to a Kaplan turbine through supply system 12 which for example comprises one or more valve(s).

[0079] An example of a control system for a system according to the invention is illustrated on FIG. 9. It comprises a processor or a computer 17 configured or programed so as to implement a process according to the invention, in particular in order: [0080] to control the system 10 for generating dry air; [0081] and/or to control the system 12; [0082] and/or to receive signal(s) 240 from sensor(s), for example sensor(s) 24, and possibly regulate the volume and /r the frequency of the inlet air flow and/or some maintenance plan based on said signal(s); [0083] and/or to control the turbine.

[0084] Alternatively, or in addition, the processor or computer 17 can be configured or programed so as to implement a process according to the invention, in particular in order to control: [0085] the generation of a flow of dry air; [0086] the supply of the turbine with said flow of said dry air; [0087] the evacuation of a flow of air out of said turbine after said flow of dry air has flowed at least through the hub.

[0088] For example said processor or a computer 17 implements a computer program comprising instructions for implementing a method according to the invention.

[0089] The device of FIGS. 3-8 can be controlled by the processor or a computer 17.

[0090] The invention allows all elements of the runner, in particular the bushing(s) and/or bearing(s) and/or the blade mechanism to operate in dry air. The invention avoids any environmental risk associated with any liquid in the runner: there can be no leakage of any kind into the water of the river, since no oil or water inhibitor or anti-bacterial additive is used.

[0091] The invention also: [0092] reduces friction and wear of most or all the internal elements and components of the hub, like self-lubricated bushing(s), which increases their life; all these components behave much better in air than in water, the invention therefore extends the life of these components and reduces the need to repair them or to repair the hub; eliminates risks associated with rust in the runner hub; [0093] extends blades mechanical life to level comparable with what is usually seen for standard Kaplan runner with oil; indeed, as already explained above, the use of dry air reduces or eliminates the presence of humidity and therefore the risk of corrosion; [0094] eliminates the galvanic corrosion risk related to water-filled Kaplan design and eliminates the impact of the water on the fatigue of the runner.

[0095] The dry air generated by the dry air generator can be used to fill the runner. As air is lighter than water, an air-filled runner improves the behaviour of the turbine regarding shaft line vibrations and critical speed and the turbine shaft fatigue life. The use of dry air ensures that the critical speed remains constant all the time: without dry air, some water can accumulate into the hub, which may results in a decrease in the critical speed after some time.