Transverse Flow Marine Turbine with Autonomous Stages

BACKGROUND

The present invention relates to transverse flow hydraulic turbine engines formed of at least one column of stacked turbines.

DISCUSSION OF THE RELATED ART

The applicant has filed a set of patent applications relative to cross-flow hydraulic turbine engines, among which:

- French patent application 04/50209 filed on Feb. 4, 2004 (B6412) relative to a cross-flow hydraulic turbine engine comprising a column of turbines, each turbine comprising blades in the form of V-shaped wings;
- French patent application 05/50420 filed on Feb. 14, 2005 (B6869) relative to a holding structure intended to stiffen a turbine column and to avoid its deformation; and
- patent application PCT/FR2008/051917 filed on Oct. 23, 2008 (B8450) relative to a turbine engine formed of an assembly of two twin columns turning in opposite directions.

These patent applications, which will be considered as known herein, describe turbine engines formed of at least one column of stacked turbines rigidly attached to a common shaft. This common shaft transmits a rotating force to a single generator associated with each column.

Patent applications 05/50420 and PCT/FR2008/051917 provide using a fairing formed of two hollow profiled walls, or wings, intended to concentrate the incident flow towards the turbines and thus increase their efficiency. In all the described cases, the fairing is one-piece, that is, a single fairing is associated with all the turbines of a column or a pair of columns. As known, the association of such a fairing with a turbine, when the walls are wing-shaped, enables, when this fairing is maintained symmetrical facing the current, to substantially multiply by two the efficiency if the chord of each wing has a length substantially equal to three times the turbine diameter.

The intensity of a sea or river current is capable of varying along time. Now, the maximum power delivered by a turbine is obtained for a speed of rotation of the drive blades which depends on the velocity of the current which reaches it. A speed variation system for controlling along time the rotation speed of the drive shaft, identical to the rotation speed of each of the turbines of a column, has thus been provided. The speed variation system may be formed from a measurement of the upstream velocity of the sea or river current which reaches the column or directly from an analysis of the power provided by the column.

Apart from having a variable intensity, the current may vary along time in terms of orientation. Such variations are observed in periodically reversing tidal currents, that is, unidirectional tides, as well as in tidal currents rotating under the effect of the Coriolis force for depths greater than approximately 10 meters. In patent applications 05/50420 and PCT/FR2008/051917, various means have been provided to force the orientation of such turbine engines, at any time and globally, according to the orientation of the current: motor assistance, or autorotation by use of vane-type tail units. The autorotation may also be ensured by placing the rotation axis of the turbine engine upstream of the two resultant forces which exert on each of the hollow profiled walls and which cross their respective thrust centers.

Except for a possible draught, the entire height of the current all the way down to the sea or river ground may be exploited by a turbine column. The latter thus face intensity variations which inevitably appear in the lower portion. In French patent application 05/50420, relative to the current intensity variation according to depth, it has been provided to arrange, between the hub of each turbine and the associated drive shaft portion, a gear box or any other system enabling to control the rotation speed of the drive blades. The arranging of such a system at the level of each turbine enables to operate each turbine of a column so that it provides a maximum power for a given orientation of the current. However, apart from its intensity variations, a current may vary according to depth and also in terms of orientation in sea cases where large-scale flow systems generate winds capable of influencing tidal currents. Now, in the disclosed system, fairings form a block associated with an entire column and it is accordingly impossible to envisage optimally adapting the fairing direction for each turbine. Finally, this system is modular neither in its structure, nor in its operation since the blocking of a turbine results in the blocking of the column.

Patent application DE-A-10065548 provides, in the field of wind turbines, a single-column turbine engine in which each stage comprises a turbine and a generator assembled on a shaft independent from that of the other stages. The installing of a system enabling to control the blade rotation speed of each turbine enables to operate each turbine optimally in terms of efficiency but also of hold of the assembly since two successive stages are capable of rotating in opposite directions. It will be underlined that this patent application relates to wind turbines and that no fairing is provided therein.

All these turbine engines have one or other of various disadvantages and do not provide an optimal efficiency.

SUMMARY

An object of embodiments of the present invention is to provide a cross-flow turbine engine structure with turbine columns cumulating the advantages, in theory incompatible, of various previous structures, to optimize the efficiency.

Another object of embodiments of the present invention is to provide a turbine engine which is particularly simple to form, to maintain, to assemble, and to disassemble.

Another object of embodiments of the present invention is to provide a turbine engine where the blocking of a turbine does not block an entire column.

Another object of embodiments of the present invention is to provide a turbine engine where each turbine may rotate at a speed optimally adapted at any time to the effective intensity of the current velocity at the turbine level.

Another object of embodiments of the present invention is to provide a turbine engine where each turbine may rotate at a speed optimally adapted at any time to the effective orientation of the current at the turbine level.

Another object of embodiments of the present invention is to provide a turbine engine having a height modularity, that is, a number of stacked turbine stages, which has no influence on the selection of the generators, thus providing a greater manufacturing modularity.

To achieve these and other objects, an embodiment of the present invention provides a turbine engine comprising a stack of stages, each of which comprises a cross-flow turbine and a generator, where each turbine-generator stage has an independent shaft, and wherein each stage is associated with an independent fairing directing it with respect to a current, each fairing being of shroud type, with symmetrical profiled wings.

According to an embodiment of the present invention, the generators of the various stages are interconnected via rectifiers.

According to an embodiment of the present invention, the output of each rectifier is coupled to independent charge means for controlling the rotation speed of the associated generator or blocking it.

According to an embodiment of the present invention, two adjacent stages are designed so that their turbines rotate in opposite directions.

According to an embodiment of the present invention, each stage is coupled to the neighboring stages by controlled means setting the mutual orientation of the stages.

According to an embodiment of the present invention, each turbine-generator-fairing stage forms an independent module stackable in situ on another module.

According to an embodiment of the present invention, each module comprises a frame comprising the two walls of a shroud-type fairing, associated with an upper plate and a lower plate; a first housing attached to the lower plate and containing the generator; and a third plate rotatably assembled with respect to the lower plate, under the housing, this third plate being provided with means of attachment to a lower module.

According to an embodiment of the present invention, the attachment means comprise pins insertable into a lower module.

According to an embodiment of the present invention, each stage comprises a couple of contra-rotating turbines, each turbine being associated with a generator contained in a housing, each turbine being separated from the other by a symmetrical profile extending downstream at least all the way to the trailing edge, each stage being separated from the neighboring stages by an upper plate and a lower plate extending from the profile all the way to the fairings.

According to an embodiment of the present invention, the blades of each turbine are of V-shaped wing type.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings, among which:

FIG. 1A is a perspective view of an example of single-column turbine engine;

FIG. 1B is a perspective view of a stage of the turbine engine of FIG. 1A;

FIG. 1C is an axial cross-section view of a stage of the turbine engine of

FIG. 1A;

FIG. 2A is a perspective view of an example of single-column turbine engine;

FIG. 2B is a simplified top view, in cross-section, of a turbine of FIG. 2A;

FIG. 2C is a cross-section view of an embodiment of a stage of the turbine engine of FIG. 2A;

FIG. 2D is a cross-section view of another embodiment of a stage of the turbine engine of FIG. 2A;

FIG. 3A is a perspective view of an example of a turbine engine with twin columns;

FIG. 3B is a perspective view of a stage of the turbine engine of FIG. 3A; and

FIG. 4 is a perspective view of an example of a turbine engine with twin columns.

DETAILED DESCRIPTION

FIGS. 1A, 1B, and 1C are simplified views respectively showing a single-column cross-flow hydraulic turbine engine, a perspective view of a stage of this turbine engine, and a partial cross-section view of a stage of this turbine engine. These views are simplified in that, especially, they do not show the means for attaching or connecting the turbine engine. Turbine engine 1 is formed of an assembly of stages 3 where each stage comprises a cross-flow turbine 5 and a generator 7. Each elementary turbine for example is of the type described in patent application 04/50209 (B6412) and is rigidly attached to a shaft 8 rotatably assembled between upper and lower flanges 9 and 10 connected by posts 11. The shafts of the various turbine-generator stages are independent from one another. Each shaft 8 drives rotor 12 of a generator 7, the rotor rotating inside of a stator 13 which provides an electric power supply via conductors 14.

Conductors 14 of the various generators are interconnected, directly in parallel or by any other connection means capable of providing an electric power supply when the turbines of the turbine engine are rotated. It may be provided to associate a rectifier with the output of each generator to allow specific independent controls of each of the generators in terms of torque and/or of rotation speed. The different rectifiers are then connected in parallel on a D.C. bus. For the connection to the network, a single inverter is necessary, placed after the D.C. bus.

Further, the adjacent turbines of a same column are preferably designed to rotate in opposite directions when a sea or river current acts on the column. For example, in the embodiment of FIG. 1A, blades 21, 22, 23, 24 of the adjacent turbines are oriented differently so that the turbines comprising blades 21 and 23 rotate in a first direction and that the turbines comprising blades 22 and 24 rotate in the opposite direction. As a result, when the column is submitted to the action of a hydraulic current, it is only submitted to a drag force which tends to give it a flexion in the current direction. Given the opposite rotation of two adjacent turbines of the column, the lift forces orthogonal to the direction of the current mutually cancel or are at least strongly decreased. The lateral load tipping moment resulting from the sum of the moments associated with the lift forces of each turbine is further decreased.

FIGS. 2A and 2B respectively are a perspective view of an example of a single-column cross-flow turbine engine and a simplified top view of a turbine and of its associated fairing.

The turbine engine comprises the same elements as FIGS. 1A to 1C, which will not be described again. Further, each stage forms a self-contained module comprising a turbine, a generator, and a frame. This frame comprises a fairing formed of two vertical or symmetrical shaped walls (or wings) 31, 32, an upper plate 41, and a lower plate, not shown in FIG. 2A. A lower fairing element 33 protects the generator. Protection elements 34 are intended to avoid any shock between the turbine blades and possible bodies driven by the current which actuates the turbine. The turbine engine is assembled in a way not shown on a foundation structure so that the lower stage can freely rotate around a vertical axis.

The top view of FIG. 2B schematically shows three blades 21A, 21B, and 21C of a turbine and two profiled wings 31, 32 of the associated fairing. Direction A corresponds to the axis of symmetry of the module and arrow C indicates the current direction. Each wing 31, 32 has a chord with an inclination relative to the axis of symmetry defined by an angle β. Angle β ranges between a value of the incidence close to critical incidence α_c(detachment), that is, substantially between 10° and 25° and an inclination of one third thereof. The detachment here is considered in the presence of turbine in the shroud, and may be different from the detachment for an isolated profile or a couple of opposite profiles. As indicated, the association of such a fairing, independent at each stage, gives the possibility of optimizing the system operation.

Thus, calling β-kβ the angle between the direction of the current and the axis of symmetry of the system, and if the turbine rotates in the direction indicated by arrow R, angle α_rbetween the chord of the wing going up with the current and direction C of the current is equal to kβ and angle α_dbetween the chord of the wing going down with the current and direction C of the current is equal to (2−k)β. The optimal direction of the fairing is that where the profiled wall corresponding to the blade motion against the current has an incidence α_rsmaller β (corresponding to a fraction k β of β, value k depending on the selected profile, on the incident velocity of the current, and on the rotation speed of the machine). In such an orientation, each blade is confronted to an overspeed (or even an underspeed if k<0 with respect to the incident velocity) which is lower when it moves against the current than if aα_r=β. On the other hand, the profiled wall corresponding to the descending motion of the blades must have an incidence α_d=(2−k)β greater than β, close to, but smaller than α_c. The overspeed is accordingly greater during the descending motion than if α_d=β. In the prior art case of a tower (a column of stages) comprising a one-piece fairing plunged in a flow with non-uniform directions, some stages, however, will have a strong efficiency drop (which may reach 50%) if incidence α_ris stronger than β by from 5 to 10 degrees.

The natural (passive) orientation of the fairing of an independent module is close to a symmetrical situation, facing the current, α_r#α_d<β for ordinary values of the advance ratio (between 2 and 5), which is the ratio of the speed of a blade tip to the current velocity. This natural orientation provides an efficiency close, to better than within 20%, to the efficiency corresponding to an optimal orientation. The optimal efficiency of the turbine is thus approached, which shows the advantage of freely rotating independent stages. It is eventually advantageous, in this case, for β to be close to α_c: the more the shroud is open, the greater the acceleration of the fluid therein (only limited by cavitation) and the higher the sampled power.

According to a variation of the present invention, instead of providing stages freely rotating with respect to one another, it may be provided to bind each stage to an adjacent stage by a motor-driven system enabling to impose or to adjust the angular shift between two stages. Thus, the passive orientation situation may be advantageously modified by a forced orientation which corresponds, at any time and for each stage, to the optimal orientation. Such a control then combines with that of the turbine rotation speed.

The use of turbine-generator-fairing stages is particularly advantageous and, in addition to efficiency gains, provides several advantages, including the following points.

Each fairing wing may be lightened with respect to prior systems where a large wing has to withstand the stress of the structure.
It becomes possible to smooth along time the stress on the holding structures in a change of tide, the stages rotating with respect to one another with a given angular shift, which avoids repositioning jolts. The structure for holding a column formed by the coupling of the stacked frames can then be lighter. Indeed, it only has to resist flexural stress in a given direction and not additional variable stress orthogonal to this direction.
The adjacent turbines of a same column may be designed to rotate in opposite directions when a sea or river current acts on the column. Given the opposite rotation of two adjacent turbines of the column, the lift forces orthogonal to the direction of the current which are exerted on the coupled frames mutually cancel or are at least strongly decreased.

FIG. 2C is a cross-section view illustrating an example of a turbine-generator-frame stage usable in the structure of FIG. 2A. This structure does not exactly correspond to the cross-section view of FIG. 2A, but illustrates certain variations which will clearly occur to those skilled in the art.

The two wings 31, 32 of the fairing are connected by an upper plate 41. This plate comprises openings 42, 43 intended to receive screws 44 of assembly to a neighboring stage. The two wings are also connected by a lower plate 45. Shaft 8 of turbine 5 is pivotally assembled on bearings 47, 48 respectively fixedly attached to upper plate 41 and to lower plate 45. Shaft 8 is connected to rotor 50 of a generator arranged on the side of plate 45 opposite to the turbine. Stator 52 of the generator is attached, for example, via a housing 53, to plate 45. A second plate 60 is assembled to freely rotate in a plane parallel to that of plate 45. The articulation between plate 60 and plate 45 is as an example formed of two circular bearings 62, 63 respectively assembled on the bottom of plate 45 and on the lateral wall of housing 53.

Of course, various alternative embodiments are possible, the important point being to have a freedom of rotation between the fairing of a stage and the underlying stage.

FIG. 2D is a cross-section view illustrating another example of a turbine-generator-fairing stage usable in the structure illustrated in FIG. 2A. While the structure of FIG. 2C is intended to be assembled before immersion (due to the presence of screws or bolts 44), the structure of FIG. 2C is intended to be assembled in situ, stage by stage. FIG. 2D shows the same elements as in FIG. 2C designated with the same reference numerals. As concerns the assembly mode, openings 42, 43 and assembly screws 44 are replaced with openings 71, 72 and pins 73, 74. Thus, the structure may be assembled in situ, stage by stage.

Among the advantages of the embodiments of FIGS. 2C and 2D, the existence of plates separating two adjacent stages should be noted. This avoids for turbulent flows created by the rotation of elements of a stage to propagate to an adjacent stage.

FIGS. 3A and 3B are perspective views of a turbine engine with twin columns and of a stage of such a turbine engine. For the design of such a structure and the forming of different variations, reference may be made to above-mentioned patent application PCT/FR2008/051917. In the shown example, the various elements of the fairing are fixed with respect to one another and the assembly is rotatably mobile around a pile 80 which is for example rotatably assembled on a fixed base.

In this embodiment, the elements of a column rotate in a direction opposite to that of the elements of the adjacent columns to suppress lift forces on the entire structure. Each stage comprises a pair of turbines 41, 42, associated with a pair of generators 43, 44.

FIG. 4 shows a turbine engine with several turbine-generator-fairing stages with twin columns forming an advantageous modification of the structure of FIG. 3A. The fairing of each of the stages is independent from the fairing of the other stages. Each stage is articulated with respect to the upper stage by means of a pile (not shown) which crosses all stages at the level of the median wall and which is attached to a foundation. The pile blocks radial and axial displacements. The freedom of rotation is provided between stages by thrust bearings around the pile.

FIG. 4 shows an example where the orientation of the current varies between the bottom and the upper portion of the structure. The current has been assumed to vary regularly. Accordingly, each of the stages is angularly shifted in the same direction with respect to the previous stage. For such a turbine engine with several twin-column turbine-generator-fairing stages, and unlike a single-column turbine engine:

the natural (passive) orientation of the fairing is exactly the symmetrical situation “facing the current”,
the optimal orientation of the fairing is exactly the natural orientation of the fairing.

Stages each comprising a turbine, a generator, and a fairing have been described, where these stages can be stacked and assembled in various manners. Specific embodiments of turbines, of generators, and of fairings have been described. It will be understood by those skilled in the art that the forming of each of these elements is likely to have many alterations, examples of which can especially be found in prior patents applications of the applicant, without this being a limitation.

The above-described turbine-generator-fairing stage stack structures combine the following features and advantages.

1. Ease of assembly/disassembly: each turbine stage can be easily stacked by engaging on another stage. Further, the turbine-generator-fairing stages described herein enable to form a turbine engine which is easy to disassemble and to transport, each stage thereof having an equivalent weight which, in practical implementations, will not exceed a value ranging between 2 and 5 tons.
2. Electric autonomy both in terms of electric conversion (one generator per turbine) and of driving of the rotation speed according to the value of the incident velocity at the considered stage, to obtain the optimal efficiency (one control system per stage). Such an independence enables to reflect an inhomogeneity in terms of altitude of the intensity of the speed. As a result of this autonomy, it is possible, if necessary, for example in the occurrence where a turbine should fail, to slow down, for example, by electrically overcharging it, the generator of an adjacent or neighboring turbine. It is finally possible to adapt the number of stages according to the implantation site without modifying the generator.
3. Mechanical autonomy: in the case where a turbine is blocked, the other turbines of the same column remain active, possibly by taking the precaution mentioned at point 2 hereabove.
4. Hydrodynamic operation independence: there is no interaction between two stacked turbines, between a turbine and its shaft, between a generator and a turbine etc., which would adversely affect the performance of each stage, due to the plates separating neighboring stages.
5. Dynamic stability of the assembly of stages against vibrations induced by lift forces, and the resonance phenomena that may result therefrom, due to the inversion of the rotation direction between stages of a column, in the case of a single-column machine.
6. Static stability of the assembly of stages against drag forces which tend to flex the column in the current direction, or even to drag away the turbine engine along the current. The tipping moments induced by such forces are much greater than those of the lift forces; they may be difficult to balance when criteria 1), 3), and the following criterion 7) are desired to be introduced.
7. Optimization of the stage orientation: significant performance gains (at least doubled) are achieved by the use of shrouds, if these shrouds result in an optimal orientation of each stage with respect to the current direction.

The present invention is likely to have various alterations and modifications which will occur to those skilled in the art, who may especially adapt various alterations described in prior publications of the inventors.

The case where two adjacent turbines of a turbine engine rotate in opposite directions has been described. Different groups of turbines rotating in opposite directions may also be provided.

Finally, the present invention has been described in the case of turbine engines operating in liquid currents (hydraulic turbine engines). The present invention may be adapted to turbine engines operating in gas currents (wind turbine engines).

Transverse Flow Marine Turbine with Autonomous Stages

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