RUNNER FOR A TIDAL POWER PLANT AND TIDAL POWER PLANT COMPRISING SUCH A RUNNER

A runner for a tidal power plant, comprising a hub body provided with openings for receiving blades, individual rotating means for rotating each blade with respect to the hub body, around an axis that is perpendicular to a rotation axis of the runner. The rotating means include at least one linear servomotor or an electric motor capable of rotating a corresponding blade independently of the other blades, over an angle superior or equal to 180° around its axis.

TECHNICAL FIELD

Embodiments of the present invention relate to a runner for a tidal power plant and a tidal power plant comprising such a runner.

BACKGROUND

Tidal power plants are arranged to convert into electricity the energy of tides. To this end, a turbine housing is generally arranged between the sea and a lagoon basin and the turbine housing includes a bulb runner comprising a hub body provided with openings for receiving blades. The bulb runner is integral to a rotating shaft which cooperates with an electricity generator.

When the water level of the sea rises with respect to the level of the lagoon, water can start flowing through the turbine to produce energy. This corresponds to the direct mode. Similarly, as the sea level starts to fall, the tidal head can be created by holding water back in the lagoon until a sufficient head is formed. Thus, the process can be reversed and the water flows in the opposite direction from the lagoon to the sea through the turbine. This corresponds to a reverse mode. In this way, generation of electricity is maximized, as it occurs with the flow of water in both directions.

In order to ensure an acceptable efficiency in both senses, it is known to orient each blade with respect to the hub body depending on the selected operating mode, that is in direct mode or in reverse mode.

A known system for achieving that goal consists in a large linear servomotor that extends within the hub body parallel to a rotation axis of the runner. A moving part of the large linear servomotor is connected to a blade lever of each blade by means of connecting rods. Therefore, the servomotor enables rotating all of the blades in a synchronized manner. However, the servomotor is designed for providing a maximum rotation of 150° about a rotation axis of the blade. As a result, the orientation of the blades in reverse mode is not satisfying and involves a significant decrease of efficiency.

SUMMARY OF THE INVENTION

It is an object of the present invention to solve the aforementioned technical problem by providing a runner for a tidal power plant having blades that can work efficiently in both operating modes.

To that end, an embodiment of the present invention concerns runner for a tidal power plant, comprising a hub body provided with openings for receiving blades, individual rotating means for rotating each blade with respect to the hub body, around an axis that is perpendicular to a rotation axis of the runner. According to an embodiment of the present invention, the rotating means include at least one linear servomotor or an electric motor capable of rotating a corresponding blade independently of the other blades, over an angle superior or equal to 180° around its axis.

In an embodiment of the present invention, when switching in reverse mode, the blades can be oriented to benefit as much as possible from hydraulic energy. Consequently, the yield of the turbine is preserved in reverse mode. Further, the rotating means used for rotating each blade are more compact than the large linear servomotor of the prior art. The diameter of the hub body is then smaller than that of a prior art runner hub body. The flow rate of water flowing around a runner according to an embodiment of the present invention is then increased with respect to the flow rate flowing around a prior art runner. Thus, the tidal power plant according to an embodiment of the present invention is more powerful.

Further aspects of the runner are beneficial but not required.

For example, in an embodiment, the blade includes a blade airfoil arranged on an external side of the hub body and a blade lever that is arranged on an internal side of the hub body and that is fixed to the blade airfoil In an embodiment, the blade airfoil bears against the outer surface of the hub body and the blade lever bears against the inner surface of the hub body.

In another embodiment, the rotating means include two linear servomotors for each blade, each linear servomotor having a fixed part which is fixed with respect to the hub body and a moving part, and two rods for each blade, the rods connecting the blade with the moving parts of the two servomotors.

In another embodiment, the rods are connected to the blade lever. Additionally, the rods may be articulated at both ends, respectively on the end of the linear servomotor moving part and on the blade.

In another embodiment, the rotating means include one linear servomotor for each blade, each linear servomotor having a fixed part which is fixed with respect to the hub body and a moving part, and a rack which is fixed to the moving part of the linear servomotor and which engages a geared pinion that is fixed with respect to the blade and that is centered on the rotation axis of the blade. In an embodiment, each linear servomotor extends parallel to the rotation axis of the runner and the moving part of each linear servomotor is a piston moving inside a housing forming the fixed part.

In another embodiment, the rotating means include a motor and a geared pinion for each blade, wherein the geared pinion is fixed with respect to the blade lever and centered on its rotation axis.

In another embodiment, the runner further includes a locking mechanism for blocking the orientation of the blades in two angular operative positions. The locking mechanism may include a retractable locking pin mounted on the hub body. Additionally, in an embodiment, the locking pin is configured to engage a recess formed in the blade lever for blocking the rotation of the blade.

In another embodiment, the locking mechanism is configured to move the locking pin between a releasing position and a locking position

The invention also relates to a tidal power plant comprising a runner as previously defined.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 to 3represent a runner2for a tidal power plant. For the clarity of the drawings, runner2is not hatched on the figures.

The tidal power plant, which is not represented in the example, is positioned between the sea and a lagoon basin. Depending on the tidal level, water may flow from the sea to the lagoon basin, which corresponds to a direct mode, or reversely, from the lagoon basin to the sea, which corresponds to a reverse mode.

Runner2is a bulb runner, suitable for being fitted into a bulb turbine. Runner2is designed for rotating around a central axis X2that is parallel to the streamflow. Axis X2is generally horizontal or slightly inclined with respect to horizontal direction. Runner2includes a hub body4that is hollow and that is secured to a rotating shaft6. In the example, bolts24are used to attach hub body4to shaft6. Shaft6is further coupled with a non-represented electricity generator for converting the mechanical energy arising from the rotation of runner2into electricity. As it can be seen onFIG. 1, hub body4is hollow and includes radial openings40for receiving blades10. Hub body4includes an internal wall42and an external wall44. Hub body4is filled with air.

Each blade10includes an airfoil portion100arranged on the external side of the hub body4and a lever portion102that is arranged on the internal side of the hub body4and that is fixed to the blade airfoil100. In the example, bolts12are used to attach lever portion102to the airfoil portion100. Blade airfoil100bears against the outer wall44of the hub body4and blade lever102bears against the inner wall42of the hub body4. Therefore, hub body4is sandwiched between blade airfoil100and blade lever102. Each blade10is movable around an axis Y10that is perpendicular to axis X2, in particular radial to axis X2. In other words, axis Y10intersects axis X2. A bearing bush is interposed, radially with respect to axis Y10, between blade10and the wall of opening40.

Runner2further includes individual rotating means8for rotating a corresponding blade10around axis Y10, with respect to the hub body4. Rotating means8enable rotating the corresponding blade10independently of the other blades, over an angle around axis Y10that is superior or equal to 180°. Individual rotating servomotors are excluded from the rotating means, as they require a lot of maintenance work and are subjected to fluid leakage. A rotating servomotor includes an internal cylinder arranged within a casing. The internal cylinder includes a protruding rib delimiting on both sides two chambers. The injection of fluid in one or other of the two chambers enables rotating the internal cylinder in the desired direction.

In the embodiment represented onFIGS. 1 to 3, rotating means8include two linear servomotors14for each blade10, each linear servomotor14having a fixed part140which is fixed with respect to the hub body4and a moving part142. Rotating means8further include two rods16for each blade10. The two linear servomotors14extend parallel to the rotation axis X2of runner2. The moving part142of each linear servomotor14is a piston moving inside a housing forming the fixed part140.

Rods16A and16B connect the blade lever102with the moving parts142of the two linear servomotors14. Connecting rods16are articulated at both ends around axes parallel to the rotation axis Y10of the blade10. More precisely, a first end160of each rod16A and16B is articulated with blade lever102, while a second end162is articulated at the end of a piston142. The end160of rod16A is hinged around a pin102A of blade lever102and the end160of rod16B is hinged around another pin102B of blade lever102.

The orientation of the blades10for switching from direct mode to reverse mode is described here-below in relation toFIGS. 2 and 3.FIG. 2represents a configuration wherein the blades10are oriented for direct mode. As the sea level starts to fall, a tidal head can be created by holding water back in the lagoon basin until a sufficient head is formed. Thus, the process can be reversed and the water flows in the opposite direction from the lagoon basin to the sea through the turbine. As a result, it is necessary to orient the blades10with respect to the streamflow direction.

The orientation of the blades10for switching in reverse mode or in direct mode is operated while the bulb turbine is not running. The tidal power plant is then equipped with means for closing the passageway between the sea and the lagoon basin. In an embodiment, the bulb turbine includes a mobile distributor and the passageway between the sea and the lagoon basin is closed by the wicket gates of the distributor. However, the tidal power plant includes two stoplogs for dewatering the turbine in order to proceed with maintenance operations.

Alternatively, the bulb turbine includes a fixed distributor. The tidal power plant then includes a gate for closing the passageway between the sea and the lagoon basin and two stoplogs for dewatering the turbine.) In an embodiment, the wicket gates of the distributor are closed when switching in direct mode or in reverse mode so that no water flows around the runner2while blades10are rotated. Thus, the means8for rotating the blades10are not oversized to compensate hydraulic forces.

Each blade10is oriented by retracting the piston142of the first servomotor14, as represented by arrow F1, and by extending piston142of the second servomotor14, as represented by arrow F2. These opposite motions mutual motions enable rotating blade lever102around axis Y10through links16A and16B, as evidenced by arrow R1.

As it can be seen by comparingFIGS. 2 and 3, the piston strokes of pistons142enable pivoting blade lever102over an angle that can be superior to 180°. In the illustrated embodiment, this angle is about 180°. This is more visible when comparing the position of pin102A or102B inFIGS. 2 and 3. The rotation R1is then sufficient to obtain an optimal orientation of the blades10both in direct mode and in reverse mode.

FIGS. 4 and 5represent a runner2for a tidal power plant, respectively according to a second and to a third embodiment of the invention. For conciseness purpose, only the differences with respect to the first embodiment are mentioned here-below. Further, components similar to that of the first embodiment keep their numerical references, while the other components have other numerical references.

In the second embodiment, rotating means8includes only one linear servomotor14for each blade10. This linear servomotor14includes a piston52designed for moving inside a housing140that is fixed with respect to the hub body4. Rotating means8further include a rack18which is fixed at one extremity142aof piston142. Rack18prolongs then the piston142parallel to axis X2. Rack18engages a geared pinion20that is fixed with respect to the blade10. In particular, geared pinion20is fixed with respect to blade lever102and centered on axis Y10. As a result, the linear displacement of piston142with respect to housing140involves the geared pinion20to rotate around axis Y10. The length of rack18together with the piston stroke of piston142inside housing140are calculated so that the blade10can be rotated around axis Y10over an angle at least superior to 180°.

In a non-represented alternative embodiment, rack18is integral with piston142.

In the third embodiment, rotating means8for rotating each blade10include an electric motor22and a geared pinion20for each blade10. More precisely, the output shaft of motor22engages geared pinion20that is fixed with respect to the blade10and centered on axis Y10.

In the illustrated embodiments, the runner2further includes a non-represented locking mechanism for each blade10. This locking mechanism is reversible and enables locking the orientation of a corresponding blade10under operating conditions, that is in two angular operative positions, respectively in direct mode and in reverse mode. In the example, this locking mechanism includes a retractable locking pin mounted on hub body4and means for moving locking pin from its locking position, wherein it engages a recess formed in blade lever102, and its releasing position, wherein it is disengaged from that recess. The means for moving the locking pin comprise two chambers. The injection of fluid in one or other of the two chambers allows engaging the locking pin into the recess or disengaging the locking pin from the recess. When the locking pin is engaged in the recess, it prevents blade10from rotating around axis Y10. One active chamber may be replaced by an elastic spring.

The locking mechanism supports centrifugal force and hydraulic forces applied on the blades10under operating conditions. As a result, the forces exerted on the rotating means8are limited.

In a non-represented alternative embodiment of the invention, other fixing means can be used to attach blade airfoil100and blade lever102. In particular, blade lever102can be welded with blade airfoil100.

In another non-represented alternative embodiment, the inner part of hub body2is filled with oil or water.

According to another non-represented alternative embodiment, the means8for rotating a corresponding blade10include an electric motor and a worm gear powered by the electric motor. The geared pinion of that system is also fixed with respect to the blade10and is centered on its rotation axis Y10. This particular embodiment is beneficial in that the worm gear is not reversible. As a result, no locking mechanism is needed to block the orientation of the corresponding blade under operating conditions.

The technical features of the different embodiments and alternative embodiments of the invention described here-above can be combined together to generate new embodiments of the invention.